# ffplay Documentation

# Table of Contents

# 1. Synopsis

    ffplay [options] [‘input_file’]

# 2. Description

FFplay is a very simple and portable media player using the FFmpeg libraries and the SDL library. It is mostly used as a testbed for the various FFmpeg APIs.

# 3. Options

All the numerical options, if not specified otherwise, accept in input a string representing a number, which may contain one of the International System number postfixes, for example ’K’, ’M’, ’G’. If ’i’ is appended after the postfix, powers of 2 are used instead of powers of 10. The ’B’ postfix multiplies the value for 8, and can be appended after another postfix or used alone. This allows using for example ’KB’, ’MiB’, ’G’ and ’B’ as postfix.

Options which do not take arguments are boolean options, and set the corresponding value to true. They can be set to false by prefixing with "no" the option name, for example using "-nofoo" in the command line will set to false the boolean option with name "foo".

## 3.1 Stream specifiers

Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers are used to precisely specify which stream(s) does a given option belong to.

A stream specifier is a string generally appended to the option name and separated from it by a colon. E.g. `-codec:a:1 ac3` option contains `a:1` stream specifer, which matches the second audio stream. Therefore it would select the ac3 codec for the second audio stream.

A stream specifier can match several stream, the option is then applied to all of them. E.g. the stream specifier in `-b:a 128k` matches all audio streams.

An empty stream specifier matches all streams, for example `-codec copy` or `-codec: copy` would copy all the streams without reencoding.

Possible forms of stream specifiers are:

‘`stream_index`’

  Matches the stream with this index. E.g. `-threads:1 4` would set the thread count for the second stream to 4.

‘`stream_type[:stream_index]`’

  stream_type is one of: ’v’ for video, ’a’ for audio, ’s’ for subtitle, ’d’ for data and ’t’ for attachments. If stream_index is given, then matches stream number stream_index of this type. Otherwise matches all streams of this type.

‘`p:program_id[:stream_index]`’

  If stream_index is given, then matches stream number stream_index in program with id program_id. Otherwise matches all streams in this program.

## 3.2 Generic options

These options are shared amongst the av* tools.

‘`-L`’

  Show license.

‘`-h, -?, -help, --help`’

  Show help.

‘`-version`’

  Show version.

‘`-formats`’

  Show available formats.

  The fields preceding the format names have the following meanings:

  ‘`D`’

    Decoding available

  ‘`E`’

    Encoding available

‘`-codecs`’

  Show available codecs.

  The fields preceding the codec names have the following meanings:

  ‘`D`’

    Decoding available

  ‘`E`’

    Encoding available

  ‘`V/A/S`’

    Video/audio/subtitle codec

  ‘`S`’

    Codec supports slices

  ‘`D`’

    Codec supports direct rendering

  ‘`T`’

    Codec can handle input truncated at random locations instead of only at frame boundaries

‘`-bsfs`’

  Show available bitstream filters.

‘`-protocols`’

  Show available protocols.

‘`-filters`’

  Show available libavfilter filters.

‘`-pix_fmts`’

  Show available pixel formats.

‘`-sample_fmts`’

  Show available sample formats.

‘`-loglevel loglevel | -v loglevel`’

  Set the logging level used by the library. loglevel is a number or a string containing one of the following values:

  ‘`quiet`’
  ‘`panic`’
  ‘`fatal`’
  ‘`error`’
  ‘`warning`’
  ‘`info`’
  ‘`verbose`’
  ‘`debug`’

  By default the program logs to stderr, if coloring is supported by the terminal, colors are used to mark errors and warnings. Log coloring can be disabled setting the environment variable `AV_LOG_FORCE_NOCOLOR` or `NO_COLOR`, or can be forced setting the environment variable `AV_LOG_FORCE_COLOR`. The use of the environment variable `NO_COLOR` is deprecated and will be dropped in a following FFmpeg version.

‘`-report`’

  Dump full command line and console output to a file named `program-YYYYMMDD-HHMMSS.log` in the current directory. This file can be useful for bug reports. It also implies `-loglevel verbose`.

  Note: setting the environment variable `FFREPORT` to any value has the same effect.

‘`-cpuflags flags (global)`’

  Allows setting and clearing cpu flags. This option is intended for testing. Do not use it unless you know what you’re doing.

      ffmpeg -cpuflags -sse+mmx ...
      ffmpeg -cpuflags mmx ...
      ffmpeg -cpuflags 0 ...

## 3.3 AVOptions

These options are provided directly by the libavformat, libavdevice and libavcodec libraries. To see the list of available AVOptions, use the ‘`-help`’ option. They are separated into two categories:

‘`generic`’

  These options can be set for any container, codec or device. Generic options are listed under AVFormatContext options for containers/devices and under AVCodecContext options for codecs.

‘`private`’

  These options are specific to the given container, device or codec. Private options are listed under their corresponding containers/devices/codecs.

For example to write an ID3v2.3 header instead of a default ID3v2.4 to an MP3 file, use the ‘`id3v2_version`’ private option of the MP3 muxer:

    ffmpeg -i input.flac -id3v2_version 3 out.mp3

All codec AVOptions are obviously per-stream, so the chapter on stream specifiers applies to them

Note ‘`-nooption`’ syntax cannot be used for boolean AVOptions, use ‘`-option 0`’/‘`-option 1`’.

Note2 old undocumented way of specifying per-stream AVOptions by prepending v/a/s to the options name is now obsolete and will be removed soon.

## 3.4 Codec AVOptions

‘`-b[:stream_specifier] integer (output,audio,video)`’

  set bitrate (in bits/s)

‘`-ab[:stream_specifier] integer (output,audio)`’

  set bitrate (in bits/s)

‘`-bt[:stream_specifier] integer (output,video)`’

  Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far ratecontrol is willing to deviate from the target average bitrate value. This is not related to min/max bitrate. Lowering tolerance too much has an adverse effect on quality.

‘`-flags[:stream_specifier] flags (input/output,audio,video)`’

  Possible values:

  ‘`mv4`’

    use four motion vector by macroblock (mpeg4)

  ‘`qpel`’

    use 1/4 pel motion compensation

  ‘`loop`’

    use loop filter

  ‘`qscale`’

    use fixed qscale

  ‘`gmc`’

    use gmc

  ‘`mv0`’

    always try a mb with mv=<0,0>

  ‘`input_preserved`’
  ‘`pass1`’

    use internal 2pass ratecontrol in first pass mode

  ‘`pass2`’

    use internal 2pass ratecontrol in second pass mode

  ‘`gray`’

    only decode/encode grayscale

  ‘`emu_edge`’

    don’t draw edges

  ‘`psnr`’

    error[?] variables will be set during encoding

  ‘`truncated`’
  ‘`naq`’

    normalize adaptive quantization

  ‘`ildct`’

    use interlaced dct

  ‘`low_delay`’

    force low delay

  ‘`global_header`’

    place global headers in extradata instead of every keyframe

  ‘`bitexact`’

    use only bitexact stuff (except (i)dct)

  ‘`aic`’

    h263 advanced intra coding / mpeg4 ac prediction

  ‘`cbp`’

    Deprecated, use mpegvideo private options instead

  ‘`qprd`’

    Deprecated, use mpegvideo private options instead

  ‘`ilme`’

    interlaced motion estimation

  ‘`cgop`’

    closed gop

‘`-sub_id[:stream_specifier] integer ()`’
‘`-me_method[:stream_specifier] integer (output,video)`’

  set motion estimation method

  Possible values:

  ‘`zero`’

    zero motion estimation (fastest)

  ‘`full`’

    full motion estimation (slowest)

  ‘`epzs`’

    EPZS motion estimation (default)

  ‘`esa`’

    esa motion estimation (alias for full)

  ‘`tesa`’

    tesa motion estimation

  ‘`dia`’

    dia motion estimation (alias for epzs)

  ‘`log`’

    log motion estimation

  ‘`phods`’

    phods motion estimation

  ‘`x1`’

    X1 motion estimation

  ‘`hex`’

    hex motion estimation

  ‘`umh`’

    umh motion estimation

  ‘`iter`’

    iter motion estimation

‘`-extradata_size[:stream_specifier] integer ()`’
‘`-time_base[:stream_specifier] rational number ()`’
‘`-g[:stream_specifier] integer (output,video)`’

  set the group of picture size

‘`-ar[:stream_specifier] integer (input/output,audio)`’

  set audio sampling rate (in Hz)

‘`-ac[:stream_specifier] integer (input/output,audio)`’

  set number of audio channels

‘`-cutoff[:stream_specifier] integer (output,audio)`’

  set cutoff bandwidth

‘`-frame_size[:stream_specifier] integer (output,audio)`’
‘`-frame_number[:stream_specifier] integer ()`’
‘`-delay[:stream_specifier] integer ()`’
‘`-qcomp[:stream_specifier] float (output,video)`’

  video quantizer scale compression (VBR). Constant of ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0

‘`-qblur[:stream_specifier] float (output,video)`’

  video quantizer scale blur (VBR)

‘`-qmin[:stream_specifier] integer (output,video)`’

  min video quantizer scale (VBR)

‘`-qmax[:stream_specifier] integer (output,video)`’

  max video quantizer scale (VBR)

‘`-qdiff[:stream_specifier] integer (output,video)`’

  max difference between the quantizer scale (VBR)

‘`-bf[:stream_specifier] integer (output,video)`’

  use ’frames’ B frames

‘`-b_qfactor[:stream_specifier] float (output,video)`’

  qp factor between p and b frames

‘`-rc_strategy[:stream_specifier] integer (output,video)`’

  ratecontrol method

‘`-b_strategy[:stream_specifier] integer (output,video)`’

  strategy to choose between I/P/B-frames

‘`-ps[:stream_specifier] integer (output,video)`’

  rtp payload size in bytes

‘`-mv_bits[:stream_specifier] integer ()`’
‘`-header_bits[:stream_specifier] integer ()`’
‘`-i_tex_bits[:stream_specifier] integer ()`’
‘`-p_tex_bits[:stream_specifier] integer ()`’
‘`-i_count[:stream_specifier] integer ()`’
‘`-p_count[:stream_specifier] integer ()`’
‘`-skip_count[:stream_specifier] integer ()`’
‘`-misc_bits[:stream_specifier] integer ()`’
‘`-frame_bits[:stream_specifier] integer ()`’
‘`-codec_tag[:stream_specifier] integer ()`’
‘`-bug[:stream_specifier] flags (input,video)`’

  workaround not auto detected encoder bugs

  Possible values:

  ‘`autodetect`’
  ‘`old_msmpeg4`’

    some old lavc generated msmpeg4v3 files (no autodetection)

  ‘`xvid_ilace`’

    Xvid interlacing bug (autodetected if fourcc==XVIX)

  ‘`ump4`’

    (autodetected if fourcc==UMP4)

  ‘`no_padding`’

    padding bug (autodetected)

  ‘`amv`’
  ‘`ac_vlc`’

    illegal vlc bug (autodetected per fourcc)

  ‘`qpel_chroma`’
  ‘`std_qpel`’

    old standard qpel (autodetected per fourcc/version)

  ‘`qpel_chroma2`’
  ‘`direct_blocksize`’

    direct-qpel-blocksize bug (autodetected per fourcc/version)

  ‘`edge`’

    edge padding bug (autodetected per fourcc/version)

  ‘`hpel_chroma`’
  ‘`dc_clip`’
  ‘`ms`’

    workaround various bugs in microsofts broken decoders

  ‘`trunc`’

    trancated frames

‘`-lelim[:stream_specifier] integer (output,video)`’

  single coefficient elimination threshold for luminance (negative values also consider dc coefficient)

‘`-celim[:stream_specifier] integer (output,video)`’

  single coefficient elimination threshold for chrominance (negative values also consider dc coefficient)

‘`-strict[:stream_specifier] integer (input/output,audio,video)`’

  how strictly to follow the standards

  Possible values:

  ‘`very`’

    strictly conform to a older more strict version of the spec or reference software

  ‘`strict`’

    strictly conform to all the things in the spec no matter what consequences

  ‘`normal`’
  ‘`unofficial`’

    allow unofficial extensions

  ‘`experimental`’

    allow non standardized experimental things

‘`-b_qoffset[:stream_specifier] float (output,video)`’

  qp offset between P and B frames

‘`-err_detect[:stream_specifier] flags (input,audio,video)`’

  set error detection flags

  Possible values:

  ‘`crccheck`’

    verify embedded CRCs

  ‘`bitstream`’

    detect bitstream specification deviations

  ‘`buffer`’

    detect improper bitstream length

  ‘`explode`’

    abort decoding on minor error detection

  ‘`careful`’

    consider things that violate the spec and have not been seen in the wild as errors

  ‘`compliant`’

    consider all spec non compliancies as errors

  ‘`aggressive`’

    consider things that a sane encoder shouldnt do as an error

‘`-has_b_frames[:stream_specifier] integer ()`’
‘`-block_align[:stream_specifier] integer ()`’
‘`-mpeg_quant[:stream_specifier] integer (output,video)`’

  use MPEG quantizers instead of H.263

‘`-stats_out[:stream_specifier] string ()`’
‘`-stats_in[:stream_specifier] string ()`’
‘`-qsquish[:stream_specifier] float (output,video)`’

  how to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function)

‘`-rc_qmod_amp[:stream_specifier] float (output,video)`’

  experimental quantizer modulation

‘`-rc_qmod_freq[:stream_specifier] integer (output,video)`’

  experimental quantizer modulation

‘`-rc_override_count[:stream_specifier] integer ()`’
‘`-rc_eq[:stream_specifier] string (output,video)`’

  Set rate control equation. When computing the expression, besides the standard functions defined in the section ’Expression Evaluation’, the following functions are available: bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.

‘`-maxrate[:stream_specifier] integer (output,audio,video)`’

  Set max bitrate tolerance (in bits/s). Requires bufsize to be set.

‘`-minrate[:stream_specifier] integer (output,audio,video)`’

  Set min bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little use elsewise.

‘`-bufsize[:stream_specifier] integer (output,audio,video)`’

  set ratecontrol buffer size (in bits)

‘`-rc_buf_aggressivity[:stream_specifier] float (output,video)`’

  currently useless

‘`-i_qfactor[:stream_specifier] float (output,video)`’

  qp factor between P and I frames

‘`-i_qoffset[:stream_specifier] float (output,video)`’

  qp offset between P and I frames

‘`-rc_init_cplx[:stream_specifier] float (output,video)`’

  initial complexity for 1-pass encoding

‘`-dct[:stream_specifier] integer (output,video)`’

  DCT algorithm

  Possible values:

  ‘`auto`’

    autoselect a good one (default)

  ‘`fastint`’

    fast integer

  ‘`int`’

    accurate integer

  ‘`mmx`’
  ‘`altivec`’
  ‘`faan`’

    floating point AAN DCT

‘`-lumi_mask[:stream_specifier] float (output,video)`’

  compresses bright areas stronger than medium ones

‘`-tcplx_mask[:stream_specifier] float (output,video)`’

  temporal complexity masking

‘`-scplx_mask[:stream_specifier] float (output,video)`’

  spatial complexity masking

‘`-p_mask[:stream_specifier] float (output,video)`’

  inter masking

‘`-dark_mask[:stream_specifier] float (output,video)`’

  compresses dark areas stronger than medium ones

‘`-idct[:stream_specifier] integer (input/output,video)`’

  select IDCT implementation

  Possible values:

  ‘`auto`’
  ‘`int`’
  ‘`simple`’
  ‘`simplemmx`’
  ‘`libmpeg2mmx`’
  ‘`mmi`’
  ‘`arm`’
  ‘`altivec`’
  ‘`sh4`’
  ‘`simplearm`’
  ‘`simplearmv5te`’
  ‘`simplearmv6`’
  ‘`simpleneon`’
  ‘`simplealpha`’
  ‘`h264`’
  ‘`vp3`’
  ‘`ipp`’
  ‘`xvidmmx`’
  ‘`faani`’

    floating point AAN IDCT

‘`-slice_count[:stream_specifier] integer ()`’
‘`-ec[:stream_specifier] flags (input,video)`’

  set error concealment strategy

  Possible values:

  ‘`guess_mvs`’

    iterative motion vector (MV) search (slow)

  ‘`deblock`’

    use strong deblock filter for damaged MBs

‘`-bits_per_coded_sample[:stream_specifier] integer ()`’
‘`-pred[:stream_specifier] integer (output,video)`’

  prediction method

  Possible values:

  ‘`left`’
  ‘`plane`’
  ‘`median`’
‘`-aspect[:stream_specifier] rational number (output,video)`’

  sample aspect ratio

‘`-debug[:stream_specifier] flags (input/output,audio,video,subtitles)`’

  print specific debug info

  Possible values:

  ‘`pict`’

    picture info

  ‘`rc`’

    rate control

  ‘`bitstream`’
  ‘`mb_type`’

    macroblock (MB) type

  ‘`qp`’

    per-block quantization parameter (QP)

  ‘`mv`’

    motion vector

  ‘`dct_coeff`’
  ‘`skip`’
  ‘`startcode`’
  ‘`pts`’
  ‘`er`’

    error recognition

  ‘`mmco`’

    memory management control operations (H.264)

  ‘`bugs`’
  ‘`vis_qp`’

    visualize quantization parameter (QP), lower QP are tinted greener

  ‘`vis_mb_type`’

    visualize block types

  ‘`buffers`’

    picture buffer allocations

  ‘`thread_ops`’

    threading operations

‘`-vismv[:stream_specifier] integer (input,video)`’

  visualize motion vectors (MVs)

  Possible values:

  ‘`pf`’

    forward predicted MVs of P-frames

  ‘`bf`’

    forward predicted MVs of B-frames

  ‘`bb`’

    backward predicted MVs of B-frames

‘`-cmp[:stream_specifier] integer (output,video)`’

  full pel me compare function

  Possible values:

  ‘`sad`’

    sum of absolute differences, fast (default)

  ‘`sse`’

    sum of squared errors

  ‘`satd`’

    sum of absolute Hadamard transformed differences

  ‘`dct`’

    sum of absolute DCT transformed differences

  ‘`psnr`’

    sum of squared quantization errors (avoid, low quality)

  ‘`bit`’

    number of bits needed for the block

  ‘`rd`’

    rate distortion optimal, slow

  ‘`zero`’

    0

  ‘`vsad`’

    sum of absolute vertical differences

  ‘`vsse`’

    sum of squared vertical differences

  ‘`nsse`’

    noise preserving sum of squared differences

  ‘`dctmax`’
  ‘`chroma`’
‘`-subcmp[:stream_specifier] integer (output,video)`’

  sub pel me compare function

  Possible values:

  ‘`sad`’

    sum of absolute differences, fast (default)

  ‘`sse`’

    sum of squared errors

  ‘`satd`’

    sum of absolute Hadamard transformed differences

  ‘`dct`’

    sum of absolute DCT transformed differences

  ‘`psnr`’

    sum of squared quantization errors (avoid, low quality)

  ‘`bit`’

    number of bits needed for the block

  ‘`rd`’

    rate distortion optimal, slow

  ‘`zero`’

    0

  ‘`vsad`’

    sum of absolute vertical differences

  ‘`vsse`’

    sum of squared vertical differences

  ‘`nsse`’

    noise preserving sum of squared differences

  ‘`dctmax`’
  ‘`chroma`’
‘`-mbcmp[:stream_specifier] integer (output,video)`’

  macroblock compare function

  Possible values:

  ‘`sad`’

    sum of absolute differences, fast (default)

  ‘`sse`’

    sum of squared errors

  ‘`satd`’

    sum of absolute Hadamard transformed differences

  ‘`dct`’

    sum of absolute DCT transformed differences

  ‘`psnr`’

    sum of squared quantization errors (avoid, low quality)

  ‘`bit`’

    number of bits needed for the block

  ‘`rd`’

    rate distortion optimal, slow

  ‘`zero`’

    0

  ‘`vsad`’

    sum of absolute vertical differences

  ‘`vsse`’

    sum of squared vertical differences

  ‘`nsse`’

    noise preserving sum of squared differences

  ‘`dctmax`’
  ‘`chroma`’
‘`-ildctcmp[:stream_specifier] integer (output,video)`’

  interlaced dct compare function

  Possible values:

  ‘`sad`’

    sum of absolute differences, fast (default)

  ‘`sse`’

    sum of squared errors

  ‘`satd`’

    sum of absolute Hadamard transformed differences

  ‘`dct`’

    sum of absolute DCT transformed differences

  ‘`psnr`’

    sum of squared quantization errors (avoid, low quality)

  ‘`bit`’

    number of bits needed for the block

  ‘`rd`’

    rate distortion optimal, slow

  ‘`zero`’

    0

  ‘`vsad`’

    sum of absolute vertical differences

  ‘`vsse`’

    sum of squared vertical differences

  ‘`nsse`’

    noise preserving sum of squared differences

  ‘`dctmax`’
  ‘`chroma`’
‘`-dia_size[:stream_specifier] integer (output,video)`’

  diamond type & size for motion estimation

‘`-last_pred[:stream_specifier] integer (output,video)`’

  amount of motion predictors from the previous frame

‘`-preme[:stream_specifier] integer (output,video)`’

  pre motion estimation

‘`-precmp[:stream_specifier] integer (output,video)`’

  pre motion estimation compare function

  Possible values:

  ‘`sad`’

    sum of absolute differences, fast (default)

  ‘`sse`’

    sum of squared errors

  ‘`satd`’

    sum of absolute Hadamard transformed differences

  ‘`dct`’

    sum of absolute DCT transformed differences

  ‘`psnr`’

    sum of squared quantization errors (avoid, low quality)

  ‘`bit`’

    number of bits needed for the block

  ‘`rd`’

    rate distortion optimal, slow

  ‘`zero`’

    0

  ‘`vsad`’

    sum of absolute vertical differences

  ‘`vsse`’

    sum of squared vertical differences

  ‘`nsse`’

    noise preserving sum of squared differences

  ‘`dctmax`’
  ‘`chroma`’
‘`-pre_dia_size[:stream_specifier] integer (output,video)`’

  diamond type & size for motion estimation pre-pass

‘`-subq[:stream_specifier] integer (output,video)`’

  sub pel motion estimation quality

‘`-dtg_active_format[:stream_specifier] integer ()`’
‘`-me_range[:stream_specifier] integer (output,video)`’

  limit motion vectors range (1023 for DivX player)

‘`-ibias[:stream_specifier] integer (output,video)`’

  intra quant bias

‘`-pbias[:stream_specifier] integer (output,video)`’

  inter quant bias

‘`-color_table_id[:stream_specifier] integer ()`’
‘`-global_quality[:stream_specifier] integer (output,audio,video)`’
‘`-coder[:stream_specifier] integer (output,video)`’

  Possible values:

  ‘`vlc`’

    variable length coder / huffman coder

  ‘`ac`’

    arithmetic coder

  ‘`raw`’

    raw (no encoding)

  ‘`rle`’

    run-length coder

  ‘`deflate`’

    deflate-based coder

‘`-context[:stream_specifier] integer (output,video)`’

  context model

‘`-slice_flags[:stream_specifier] integer ()`’
‘`-xvmc_acceleration[:stream_specifier] integer ()`’
‘`-mbd[:stream_specifier] integer (output,video)`’

  macroblock decision algorithm (high quality mode)

  Possible values:

  ‘`simple`’

    use mbcmp (default)

  ‘`bits`’

    use fewest bits

  ‘`rd`’

    use best rate distortion

‘`-stream_codec_tag[:stream_specifier] integer ()`’
‘`-sc_threshold[:stream_specifier] integer (output,video)`’

  scene change threshold

‘`-lmin[:stream_specifier] integer (output,video)`’

  min lagrange factor (VBR)

‘`-lmax[:stream_specifier] integer (output,video)`’

  max lagrange factor (VBR)

‘`-nr[:stream_specifier] integer (output,video)`’

  noise reduction

‘`-rc_init_occupancy[:stream_specifier] integer (output,video)`’

  number of bits which should be loaded into the rc buffer before decoding starts

‘`-inter_threshold[:stream_specifier] integer (output,video)`’
‘`-flags2[:stream_specifier] flags (input/output,audio,video)`’

  Possible values:

  ‘`fast`’

    allow non spec compliant speedup tricks

  ‘`sgop`’

    Deprecated, use mpegvideo private options instead

  ‘`noout`’

    skip bitstream encoding

  ‘`local_header`’

    place global headers at every keyframe instead of in extradata

  ‘`chunks`’

    Frame data might be split into multiple chunks

  ‘`showall`’

    Show all frames before the first keyframe

  ‘`skiprd`’

    Deprecated, use mpegvideo private options instead

‘`-error[:stream_specifier] integer (output,video)`’
‘`-qns[:stream_specifier] integer (output,video)`’

  deprecated, use mpegvideo private options instead

‘`-threads[:stream_specifier] integer (input/output,video)`’

  Possible values:

  ‘`auto`’

    detect a good number of threads

‘`-me_threshold[:stream_specifier] integer (output,video)`’

  motion estimaton threshold

‘`-mb_threshold[:stream_specifier] integer (output,video)`’

  macroblock threshold

‘`-dc[:stream_specifier] integer (output,video)`’

  intra_dc_precision

‘`-nssew[:stream_specifier] integer (output,video)`’

  nsse weight

‘`-skip_top[:stream_specifier] integer (input,video)`’

  number of macroblock rows at the top which are skipped

‘`-skip_bottom[:stream_specifier] integer (input,video)`’

  number of macroblock rows at the bottom which are skipped

‘`-profile[:stream_specifier] integer (output,audio,video)`’

  Possible values:

  ‘`unknown`’
  ‘`aac_main`’
  ‘`aac_low`’
  ‘`aac_ssr`’
  ‘`aac_ltp`’
  ‘`dts`’
  ‘`dts_es`’
  ‘`dts_96_24`’
  ‘`dts_hd_hra`’
  ‘`dts_hd_ma`’
‘`-level[:stream_specifier] integer (output,audio,video)`’

  Possible values:

  ‘`unknown`’
‘`-lowres[:stream_specifier] integer (input,audio,video)`’

  decode at 1= 1/2, 2=1/4, 3=1/8 resolutions

‘`-skip_threshold[:stream_specifier] integer (output,video)`’

  frame skip threshold

‘`-skip_factor[:stream_specifier] integer (output,video)`’

  frame skip factor

‘`-skip_exp[:stream_specifier] integer (output,video)`’

  frame skip exponent

‘`-skipcmp[:stream_specifier] integer (output,video)`’

  frame skip compare function

  Possible values:

  ‘`sad`’

    sum of absolute differences, fast (default)

  ‘`sse`’

    sum of squared errors

  ‘`satd`’

    sum of absolute Hadamard transformed differences

  ‘`dct`’

    sum of absolute DCT transformed differences

  ‘`psnr`’

    sum of squared quantization errors (avoid, low quality)

  ‘`bit`’

    number of bits needed for the block

  ‘`rd`’

    rate distortion optimal, slow

  ‘`zero`’

    0

  ‘`vsad`’

    sum of absolute vertical differences

  ‘`vsse`’

    sum of squared vertical differences

  ‘`nsse`’

    noise preserving sum of squared differences

  ‘`dctmax`’
  ‘`chroma`’
‘`-border_mask[:stream_specifier] float (output,video)`’

  increases the quantizer for macroblocks close to borders

‘`-mblmin[:stream_specifier] integer (output,video)`’

  min macroblock lagrange factor (VBR)

‘`-mblmax[:stream_specifier] integer (output,video)`’

  max macroblock lagrange factor (VBR)

‘`-mepc[:stream_specifier] integer (output,video)`’

  motion estimation bitrate penalty compensation (1.0 = 256)

‘`-skip_loop_filter[:stream_specifier] integer (input,video)`’

  Possible values:

  ‘`none`’
  ‘`default`’
  ‘`noref`’
  ‘`bidir`’
  ‘`nokey`’
  ‘`all`’
‘`-skip_idct[:stream_specifier] integer (input,video)`’

  Possible values:

  ‘`none`’
  ‘`default`’
  ‘`noref`’
  ‘`bidir`’
  ‘`nokey`’
  ‘`all`’
‘`-skip_frame[:stream_specifier] integer (input,video)`’

  Possible values:

  ‘`none`’
  ‘`default`’
  ‘`noref`’
  ‘`bidir`’
  ‘`nokey`’
  ‘`all`’
‘`-bidir_refine[:stream_specifier] integer (output,video)`’

  refine the two motion vectors used in bidirectional macroblocks

‘`-brd_scale[:stream_specifier] integer (output,video)`’

  downscales frames for dynamic B-frame decision

‘`-keyint_min[:stream_specifier] integer (output,video)`’

  minimum interval between IDR-frames

‘`-refs[:stream_specifier] integer (output,video)`’

  reference frames to consider for motion compensation

‘`-chromaoffset[:stream_specifier] integer (output,video)`’

  chroma qp offset from luma

‘`-trellis[:stream_specifier] integer (output,audio,video)`’

  rate-distortion optimal quantization

‘`-sc_factor[:stream_specifier] integer (output,video)`’

  multiplied by qscale for each frame and added to scene_change_score

‘`-mv0_threshold[:stream_specifier] integer (output,video)`’
‘`-b_sensitivity[:stream_specifier] integer (output,video)`’

  adjusts sensitivity of b_frame_strategy 1

‘`-compression_level[:stream_specifier] integer (output,audio,video)`’
‘`-min_prediction_order[:stream_specifier] integer (output,audio)`’
‘`-max_prediction_order[:stream_specifier] integer (output,audio)`’
‘`-timecode_frame_start[:stream_specifier] integer (output,video)`’

  GOP timecode frame start number, in non drop frame format

‘`-request_channels[:stream_specifier] integer (input,audio)`’

  set desired number of audio channels

‘`-bits_per_raw_sample[:stream_specifier] integer ()`’
‘`-channel_layout[:stream_specifier] integer (input/output,audio)`’

  Possible values:

‘`-request_channel_layout[:stream_specifier] integer (input,audio)`’

  Possible values:

‘`-rc_max_vbv_use[:stream_specifier] float (output,video)`’
‘`-rc_min_vbv_use[:stream_specifier] float (output,video)`’
‘`-ticks_per_frame[:stream_specifier] integer (input/output,audio,video)`’
‘`-color_primaries[:stream_specifier] integer (input/output,video)`’
‘`-color_trc[:stream_specifier] integer (input/output,video)`’
‘`-colorspace[:stream_specifier] integer (input/output,video)`’
‘`-color_range[:stream_specifier] integer (input/output,video)`’
‘`-chroma_sample_location[:stream_specifier] integer (input/output,video)`’
‘`-log_level_offset[:stream_specifier] integer ()`’

  set the log level offset

‘`-slices[:stream_specifier] integer (output,video)`’

  number of slices, used in parallelized encoding

‘`-thread_type[:stream_specifier] flags (input/output,video)`’

  select multithreading type

  Possible values:

  ‘`slice`’
  ‘`frame`’
‘`-audio_service_type[:stream_specifier] integer (output,audio)`’

  audio service type

  Possible values:

  ‘`ma`’

    Main Audio Service

  ‘`ef`’

    Effects

  ‘`vi`’

    Visually Impaired

  ‘`hi`’

    Hearing Impaired

  ‘`di`’

    Dialogue

  ‘`co`’

    Commentary

  ‘`em`’

    Emergency

  ‘`vo`’

    Voice Over

  ‘`ka`’

    Karaoke

‘`-request_sample_fmt[:stream_specifier] integer (input,audio)`’

  sample format audio decoders should prefer

  Possible values:

  ‘`u8`’

    8-bit unsigned integer

  ‘`s16`’

    16-bit signed integer

  ‘`s32`’

    32-bit signed integer

  ‘`flt`’

    32-bit float

  ‘`dbl`’

    64-bit double

## 3.5 Format AVOptions

‘`-avioflags flags (input/output)`’

  Possible values:

  ‘`direct`’

    reduce buffering

‘`-probesize integer (input)`’

  set probing size

‘`-packetsize integer (output)`’

  set packet size

‘`-fflags flags (input/output)`’

  Possible values:

  ‘`ignidx`’

    ignore index

  ‘`genpts`’

    generate pts

  ‘`nofillin`’

    do not fill in missing values that can be exactly calculated

  ‘`noparse`’

    disable AVParsers, this needs nofillin too

  ‘`igndts`’

    ignore dts

  ‘`discardcorrupt`’

    discard corrupted frames

  ‘`sortdts`’

    try to interleave outputted packets by dts

  ‘`keepside`’

    dont merge side data

  ‘`latm`’

    enable RTP MP4A-LATM payload

‘`-analyzeduration integer (input)`’

  how many microseconds are analyzed to estimate duration

‘`-cryptokey hexadecimal string (input)`’

  decryption key

‘`-indexmem integer (input)`’

  max memory used for timestamp index (per stream)

‘`-rtbufsize integer (input)`’

  max memory used for buffering real-time frames

‘`-fdebug flags (input/output)`’

  print specific debug info

  Possible values:

  ‘`ts`’
‘`-max_delay integer (input/output)`’

  maximum muxing or demuxing delay in microseconds

‘`-fpsprobesize integer (input)`’

  number of frames used to probe fps

‘`-audio_preload integer (output)`’

  microseconds by which audio packets should be interleaved earlier

‘`-chunk_duration integer (output)`’

  microseconds for each chunk

‘`-chunk_size integer (output)`’

  size in bytes for each chunk

‘`-f_err_detect flags (input)`’

  set error detection flags (deprecated; use err_detect, save via avconv)

  Possible values:

  ‘`crccheck`’

    verify embedded CRCs

  ‘`bitstream`’

    detect bitstream specification deviations

  ‘`buffer`’

    detect improper bitstream length

  ‘`explode`’

    abort decoding on minor error detection

  ‘`careful`’

    consider things that violate the spec and have not been seen in the wild as errors

  ‘`compliant`’

    consider all spec non compliancies as errors

  ‘`aggressive`’

    consider things that a sane encoder shouldnt do as an error

‘`-err_detect flags (input)`’

  set error detection flags

  Possible values:

  ‘`crccheck`’

    verify embedded CRCs

  ‘`bitstream`’

    detect bitstream specification deviations

  ‘`buffer`’

    detect improper bitstream length

  ‘`explode`’

    abort decoding on minor error detection

  ‘`careful`’

    consider things that violate the spec and have not been seen in the wild as errors

  ‘`compliant`’

    consider all spec non compliancies as errors

  ‘`aggressive`’

    consider things that a sane encoder shouldnt do as an error

## 3.6 Main options

‘`-x width`’

  Force displayed width.

‘`-y height`’

  Force displayed height.

‘`-s size`’

  Set frame size (WxH or abbreviation), needed for videos which do not contain a header with the frame size like raw YUV. This option has been deprecated in favor of private options, try -video_size.

‘`-an`’

  Disable audio.

‘`-vn`’

  Disable video.

‘`-ss pos`’

  Seek to a given position in seconds.

‘`-t duration`’

  play <duration> seconds of audio/video

‘`-bytes`’

  Seek by bytes.

‘`-nodisp`’

  Disable graphical display.

‘`-f fmt`’

  Force format.

‘`-window_title title`’

  Set window title (default is the input filename).

‘`-loop number`’

  Loops movie playback <number> times. 0 means forever.

‘`-showmode mode`’

  Set the show mode to use. Available values for mode are:

  ‘`0, video`’

    show video

  ‘`1, waves`’

    show audio waves

  ‘`2, rdft`’

    show audio frequency band using RDFT ((Inverse) Real Discrete Fourier Transform)

  Default value is "video", if video is not present or cannot be played "rdft" is automatically selected.

  You can interactively cycle through the available show modes by pressing the key <w>.

‘`-vf filter_graph`’

  filter_graph is a description of the filter graph to apply to the input video. Use the option "-filters" to show all the available filters (including also sources and sinks).

‘`-i input_file`’

  Read input_file.

## 3.7 Advanced options

‘`-pix_fmt format`’

  Set pixel format. This option has been deprecated in favor of private options, try -pixel_format.

‘`-stats`’

  Show the stream duration, the codec parameters, the current position in the stream and the audio/video synchronisation drift.

‘`-bug`’

  Work around bugs.

‘`-fast`’

  Non-spec-compliant optimizations.

‘`-genpts`’

  Generate pts.

‘`-rtp_tcp`’

  Force RTP/TCP protocol usage instead of RTP/UDP. It is only meaningful if you are streaming with the RTSP protocol.

‘`-sync type`’

  Set the master clock to audio (`type=audio`), video (`type=video`) or external (`type=ext`). Default is audio. The master clock is used to control audio-video synchronization. Most media players use audio as master clock, but in some cases (streaming or high quality broadcast) it is necessary to change that. This option is mainly used for debugging purposes.

‘`-threads count`’

  Set the thread count.

‘`-ast audio_stream_number`’

  Select the desired audio stream number, counting from 0. The number refers to the list of all the input audio streams. If it is greater than the number of audio streams minus one, then the last one is selected, if it is negative the audio playback is disabled.

‘`-vst video_stream_number`’

  Select the desired video stream number, counting from 0. The number refers to the list of all the input video streams. If it is greater than the number of video streams minus one, then the last one is selected, if it is negative the video playback is disabled.

‘`-sst subtitle_stream_number`’

  Select the desired subtitle stream number, counting from 0. The number refers to the list of all the input subtitle streams. If it is greater than the number of subtitle streams minus one, then the last one is selected, if it is negative the subtitle rendering is disabled.

‘`-autoexit`’

  Exit when video is done playing.

‘`-exitonkeydown`’

  Exit if any key is pressed.

‘`-exitonmousedown`’

  Exit if any mouse button is pressed.

‘`-codec:stream_type`’

  Force a specific decoder implementation

## 3.8 While playing

<q, ESC>

  Quit.

<f>

  Toggle full screen.

<p, SPC>

  Pause.

<a>

  Cycle audio channel.

<v>

  Cycle video channel.

<t>

  Cycle subtitle channel.

<w>

  Show audio waves.

<left/right>

  Seek backward/forward 10 seconds.

<down/up>

  Seek backward/forward 1 minute.

<page down/page up>

  Seek backward/forward 10 minutes.

<mouse click>

  Seek to percentage in file corresponding to fraction of width.

# 4. Expression Evaluation

When evaluating an arithmetic expression, FFmpeg uses an internal formula evaluator, implemented through the ‘`libavutil/eval.h`’ interface.

An expression may contain unary, binary operators, constants, and functions.

Two expressions expr1 and expr2 can be combined to form another expression "expr1;expr2". expr1 and expr2 are evaluated in turn, and the new expression evaluates to the value of expr2.

The following binary operators are available: `+`, `-`, `*`, `/`, `^`.

The following unary operators are available: `+`, `-`.

The following functions are available:

‘`sinh(x)`’
‘`cosh(x)`’
‘`tanh(x)`’
‘`sin(x)`’
‘`cos(x)`’
‘`tan(x)`’
‘`atan(x)`’
‘`asin(x)`’
‘`acos(x)`’
‘`exp(x)`’
‘`log(x)`’
‘`abs(x)`’
‘`squish(x)`’
‘`gauss(x)`’
‘`isnan(x)`’

  Return 1.0 if x is NAN, 0.0 otherwise.

‘`mod(x, y)`’
‘`max(x, y)`’
‘`min(x, y)`’
‘`eq(x, y)`’
‘`gte(x, y)`’
‘`gt(x, y)`’
‘`lte(x, y)`’
‘`lt(x, y)`’
‘`st(var, expr)`’

  Allow to store the value of the expression expr in an internal variable. var specifies the number of the variable where to store the value, and it is a value ranging from 0 to 9. The function returns the value stored in the internal variable. Note, Variables are currently not shared between expressions.

‘`ld(var)`’

  Allow to load the value of the internal variable with number var, which was previously stored with st(var, expr). The function returns the loaded value.

‘`while(cond, expr)`’

  Evaluate expression expr while the expression cond is non-zero, and returns the value of the last expr evaluation, or NAN if cond was always false.

‘`ceil(expr)`’

  Round the value of expression expr upwards to the nearest integer. For example, "ceil(1.5)" is "2.0".

‘`floor(expr)`’

  Round the value of expression expr downwards to the nearest integer. For example, "floor(-1.5)" is "-2.0".

‘`trunc(expr)`’

  Round the value of expression expr towards zero to the nearest integer. For example, "trunc(-1.5)" is "-1.0".

‘`sqrt(expr)`’

  Compute the square root of expr. This is equivalent to "(expr)^.5".

‘`not(expr)`’

  Return 1.0 if expr is zero, 0.0 otherwise.

‘`pow(x, y)`’

  Compute the power of x elevated y, it is equivalent to "(x)^(y)".

‘`random(x)`’

  Return a pseudo random value between 0.0 and 1.0. x is the index of the internal variable which will be used to save the seed/state.

‘`hypot(x, y)`’

  This function is similar to the C function with the same name; it returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right triangle with sides of length x and y, or the distance of the point (x, y) from the origin.

‘`gcd(x, y)`’

  Return the greatest common divisor of x and y. If both x and y are 0 or either or both are less than zero then behavior is undefined.

‘`if(x, y)`’

  Evaluate x, and if the result is non-zero return the result of the evaluation of y, return 0 otherwise.

‘`ifnot(x, y)`’

  Evaluate x, and if the result is zero return the result of the evaluation of y, return 0 otherwise.

‘`taylor(expr, x) taylor(expr, x, id)`’

  Evaluate a taylor series at x. expr represents the LD(id)-th derivates of f(x) at 0. If id is not specified then 0 is assumed. note, when you have the derivatives at y instead of 0 taylor(expr, x-y) can be used When the series does not converge the results are undefined.

‘`root(expr, max)`’

  Finds x where f(x)=0 in the interval 0..max. f() must be continuous or the result is undefined.

The following constants are available:

‘`PI`’

  area of the unit disc, approximately 3.14

‘`E`’

  exp(1) (Euler’s number), approximately 2.718

‘`PHI`’

  golden ratio (1+sqrt(5))/2, approximately 1.618

Assuming that an expression is considered "true" if it has a non-zero value, note that:

`*` works like AND

`+` works like OR

and the construct:

    if A then B else C

is equivalent to

    if(A,B) + ifnot(A,C)

In your C code, you can extend the list of unary and binary functions, and define recognized constants, so that they are available for your expressions.

The evaluator also recognizes the International System number postfixes. If ’i’ is appended after the postfix, powers of 2 are used instead of powers of 10. The ’B’ postfix multiplies the value for 8, and can be appended after another postfix or used alone. This allows using for example ’KB’, ’MiB’, ’G’ and ’B’ as postfix.

Follows the list of available International System postfixes, with indication of the corresponding powers of 10 and of 2.

‘`y`’

  -24 / -80

‘`z`’

  -21 / -70

‘`a`’

  -18 / -60

‘`f`’

  -15 / -50

‘`p`’

  -12 / -40

‘`n`’

  -9 / -30

‘`u`’

  -6 / -20

‘`m`’

  -3 / -10

‘`c`’

  -2

‘`d`’

  -1

‘`h`’

  2

‘`k`’

  3 / 10

‘`K`’

  3 / 10

‘`M`’

  6 / 20

‘`G`’

  9 / 30

‘`T`’

  12 / 40

‘`P`’

  15 / 40

‘`E`’

  18 / 50

‘`Z`’

  21 / 60

‘`Y`’

  24 / 70

# 5. Decoders

Decoders are configured elements in FFmpeg which allow the decoding of multimedia streams.

When you configure your FFmpeg build, all the supported native decoders are enabled by default. Decoders requiring an external library must be enabled manually via the corresponding `--enable-lib` option. You can list all available decoders using the configure option `--list-decoders`.

You can disable all the decoders with the configure option `--disable-decoders` and selectively enable / disable single decoders with the options `--enable-decoder=DECODER` / `--disable-decoder=DECODER`.

The option `-codecs` of the ff* tools will display the list of enabled decoders.

# 6. Video Decoders

A description of some of the currently available video decoders follows.

## 6.1 rawvideo

Raw video decoder.

This decoder decodes rawvideo streams.

### 6.1.1 Options

‘`top top_field_first`’

  Specify the assumed field type of the input video.

  ‘`-1`’

    the video is assumed to be progressive (default)

  ‘`0`’

    bottom-field-first is assumed

  ‘`1`’

    top-field-first is assumed

# 7. Audio Decoders

## 7.1 ffwavesynth

Internal wave synthetizer.

This decoder generates wave patterns according to predefined sequences. Its use is purely internal and the format of the data it accepts is not publicly documented.

# 8. Demuxers

Demuxers are configured elements in FFmpeg which allow to read the multimedia streams from a particular type of file.

When you configure your FFmpeg build, all the supported demuxers are enabled by default. You can list all available ones using the configure option "–list-demuxers".

You can disable all the demuxers using the configure option "–disable-demuxers", and selectively enable a single demuxer with the option "–enable-demuxer=DEMUXER", or disable it with the option "–disable-demuxer=DEMUXER".

The option "-formats" of the ff* tools will display the list of enabled demuxers.

The description of some of the currently available demuxers follows.

## 8.1 image2

Image file demuxer.

This demuxer reads from a list of image files specified by a pattern.

The pattern may contain the string "%d" or "%0Nd", which specifies the position of the characters representing a sequential number in each filename matched by the pattern. If the form "%d0Nd" is used, the string representing the number in each filename is 0-padded and N is the total number of 0-padded digits representing the number. The literal character ’%’ can be specified in the pattern with the string "%%".

If the pattern contains "%d" or "%0Nd", the first filename of the file list specified by the pattern must contain a number inclusively contained between 0 and 4, all the following numbers must be sequential. This limitation may be hopefully fixed.

The pattern may contain a suffix which is used to automatically determine the format of the images contained in the files.

For example the pattern "img-%03d.bmp" will match a sequence of filenames of the form ‘`img-001.bmp`’, ‘`img-002.bmp`’, ..., ‘`img-010.bmp`’, etc.; the pattern "i%%m%%g-%d.jpg" will match a sequence of filenames of the form ‘`i%m%g-1.jpg`’, ‘`i%m%g-2.jpg`’, ..., ‘`i%m%g-10.jpg`’, etc.

The size, the pixel format, and the format of each image must be the same for all the files in the sequence.

The following example shows how to use `ffmpeg` for creating a video from the images in the file sequence ‘`img-001.jpeg`’, ‘`img-002.jpeg`’, ..., assuming an input frame rate of 10 frames per second:

    ffmpeg -i 'img-%03d.jpeg' -r 10 out.mkv

Note that the pattern must not necessarily contain "%d" or "%0Nd", for example to convert a single image file ‘`img.jpeg`’ you can employ the command:

    ffmpeg -i img.jpeg img.png

## 8.2 applehttp

Apple HTTP Live Streaming demuxer.

This demuxer presents all AVStreams from all variant streams. The id field is set to the bitrate variant index number. By setting the discard flags on AVStreams (by pressing ’a’ or ’v’ in ffplay), the caller can decide which variant streams to actually receive. The total bitrate of the variant that the stream belongs to is available in a metadata key named "variant_bitrate".

## 8.3 sbg

SBaGen script demuxer.

This demuxer reads the script language used by SBaGen http://uazu.net/sbagen/ to generate binaural beats sessions. A SBG script looks like that:

    -SE
    a: 300-2.5/3 440+4.5/0
    b: 300-2.5/0 440+4.5/3
    off: -
    NOW      == a
    +0:07:00 == b
    +0:14:00 == a
    +0:21:00 == b
    +0:30:00    off

A SBG script can mix absolute and relative timestamps. If the script uses either only absolute timestamps (including the script start time) or only relative ones, then its layout is fixed, and the conversion is straightforward. On the other hand, if the script mixes both kind of timestamps, then the NOW reference for relative timestamps will be taken from the current time of day at the time the script is read, and the script layout will be frozen according to that reference. That means that if the script is directly played, the actual times will match the absolute timestamps up to the sound controller’s clock accuracy, but if the user somehow pauses the playback or seeks, all times will be shifted accordingly.

# 9. Muxers

Muxers are configured elements in FFmpeg which allow writing multimedia streams to a particular type of file.

When you configure your FFmpeg build, all the supported muxers are enabled by default. You can list all available muxers using the configure option `--list-muxers`.

You can disable all the muxers with the configure option `--disable-muxers` and selectively enable / disable single muxers with the options `--enable-muxer=MUXER` / `--disable-muxer=MUXER`.

The option `-formats` of the ff* tools will display the list of enabled muxers.

A description of some of the currently available muxers follows.

## 9.1 crc

CRC (Cyclic Redundancy Check) testing format.

This muxer computes and prints the Adler-32 CRC of all the input audio and video frames. By default audio frames are converted to signed 16-bit raw audio and video frames to raw video before computing the CRC.

The output of the muxer consists of a single line of the form: CRC=0xCRC, where CRC is a hexadecimal number 0-padded to 8 digits containing the CRC for all the decoded input frames.

For example to compute the CRC of the input, and store it in the file ‘`out.crc`’:

    ffmpeg -i INPUT -f crc out.crc

You can print the CRC to stdout with the command:

    ffmpeg -i INPUT -f crc -

You can select the output format of each frame with `ffmpeg` by specifying the audio and video codec and format. For example to compute the CRC of the input audio converted to PCM unsigned 8-bit and the input video converted to MPEG-2 video, use the command:

    ffmpeg -i INPUT -c:a pcm_u8 -c:v mpeg2video -f crc -

See also the framecrc muxer.

## 9.2 framecrc

Per-packet CRC (Cyclic Redundancy Check) testing format.

This muxer computes and prints the Adler-32 CRC for each audio and video packet. By default audio frames are converted to signed 16-bit raw audio and video frames to raw video before computing the CRC.

The output of the muxer consists of a line for each audio and video packet of the form:

    stream_index, packet_dts, packet_pts, packet_duration, packet_size, 0xCRC

CRC is a hexadecimal number 0-padded to 8 digits containing the CRC of the packet.

For example to compute the CRC of the audio and video frames in ‘`INPUT`’, converted to raw audio and video packets, and store it in the file ‘`out.crc`’:

    ffmpeg -i INPUT -f framecrc out.crc

To print the information to stdout, use the command:

    ffmpeg -i INPUT -f framecrc -

With `ffmpeg`, you can select the output format to which the audio and video frames are encoded before computing the CRC for each packet by specifying the audio and video codec. For example, to compute the CRC of each decoded input audio frame converted to PCM unsigned 8-bit and of each decoded input video frame converted to MPEG-2 video, use the command:

    ffmpeg -i INPUT -c:a pcm_u8 -c:v mpeg2video -f framecrc -

See also the crc muxer.

## 9.3 framemd5

Per-packet MD5 testing format.

This muxer computes and prints the MD5 hash for each audio and video packet. By default audio frames are converted to signed 16-bit raw audio and video frames to raw video before computing the hash.

The output of the muxer consists of a line for each audio and video packet of the form:

    stream_index, packet_dts, packet_pts, packet_duration, packet_size, MD5

MD5 is a hexadecimal number representing the computed MD5 hash for the packet.

For example to compute the MD5 of the audio and video frames in ‘`INPUT`’, converted to raw audio and video packets, and store it in the file ‘`out.md5`’:

    ffmpeg -i INPUT -f framemd5 out.md5

To print the information to stdout, use the command:

    ffmpeg -i INPUT -f framemd5 -

See also the md5 muxer.

## 9.4 image2

Image file muxer.

The image file muxer writes video frames to image files.

The output filenames are specified by a pattern, which can be used to produce sequentially numbered series of files. The pattern may contain the string "%d" or "%0Nd", this string specifies the position of the characters representing a numbering in the filenames. If the form "%0Nd" is used, the string representing the number in each filename is 0-padded to N digits. The literal character ’%’ can be specified in the pattern with the string "%%".

If the pattern contains "%d" or "%0Nd", the first filename of the file list specified will contain the number 1, all the following numbers will be sequential.

The pattern may contain a suffix which is used to automatically determine the format of the image files to write.

For example the pattern "img-%03d.bmp" will specify a sequence of filenames of the form ‘`img-001.bmp`’, ‘`img-002.bmp`’, ..., ‘`img-010.bmp`’, etc. The pattern "img%%-%d.jpg" will specify a sequence of filenames of the form ‘`img%-1.jpg`’, ‘`img%-2.jpg`’, ..., ‘`img%-10.jpg`’, etc.

The following example shows how to use `ffmpeg` for creating a sequence of files ‘`img-001.jpeg`’, ‘`img-002.jpeg`’, ..., taking one image every second from the input video:

    ffmpeg -i in.avi -vsync 1 -r 1 -f image2 'img-%03d.jpeg'

Note that with `ffmpeg`, if the format is not specified with the `-f` option and the output filename specifies an image file format, the image2 muxer is automatically selected, so the previous command can be written as:

    ffmpeg -i in.avi -vsync 1 -r 1 'img-%03d.jpeg'

Note also that the pattern must not necessarily contain "%d" or "%0Nd", for example to create a single image file ‘`img.jpeg`’ from the input video you can employ the command:

    ffmpeg -i in.avi -f image2 -frames:v 1 img.jpeg

The image muxer supports the .Y.U.V image file format. This format is special in that that each image frame consists of three files, for each of the YUV420P components. To read or write this image file format, specify the name of the ’.Y’ file. The muxer will automatically open the ’.U’ and ’.V’ files as required.

## 9.5 md5

MD5 testing format.

This muxer computes and prints the MD5 hash of all the input audio and video frames. By default audio frames are converted to signed 16-bit raw audio and video frames to raw video before computing the hash.

The output of the muxer consists of a single line of the form: MD5=MD5, where MD5 is a hexadecimal number representing the computed MD5 hash.

For example to compute the MD5 hash of the input converted to raw audio and video, and store it in the file ‘`out.md5`’:

    ffmpeg -i INPUT -f md5 out.md5

You can print the MD5 to stdout with the command:

    ffmpeg -i INPUT -f md5 -

See also the framemd5 muxer.

## 9.6 MOV/MP4/ISMV

The mov/mp4/ismv muxer supports fragmentation. Normally, a MOV/MP4 file has all the metadata about all packets stored in one location (written at the end of the file, it can be moved to the start for better playback using the `qt-faststart` tool). A fragmented file consists of a number of fragments, where packets and metadata about these packets are stored together. Writing a fragmented file has the advantage that the file is decodable even if the writing is interrupted (while a normal MOV/MP4 is undecodable if it is not properly finished), and it requires less memory when writing very long files (since writing normal MOV/MP4 files stores info about every single packet in memory until the file is closed). The downside is that it is less compatible with other applications.

Fragmentation is enabled by setting one of the AVOptions that define how to cut the file into fragments:

‘`-moov_size bytes`’

  Reserves space for the moov atom at the beginning of the file instead of placing the moov atom at the end. If the space reserved is insufficient, muxing will fail.

‘`-movflags frag_keyframe`’

  Start a new fragment at each video keyframe.

‘`-frag_duration duration`’

  Create fragments that are duration microseconds long.

‘`-frag_size size`’

  Create fragments that contain up to size bytes of payload data.

‘`-movflags frag_custom`’

  Allow the caller to manually choose when to cut fragments, by calling `av_write_frame(ctx, NULL)` to write a fragment with the packets written so far. (This is only useful with other applications integrating libavformat, not from `ffmpeg`.)

‘`-min_frag_duration duration`’

  Don’t create fragments that are shorter than duration microseconds long.

If more than one condition is specified, fragments are cut when one of the specified conditions is fulfilled. The exception to this is `-min_frag_duration`, which has to be fulfilled for any of the other conditions to apply.

Additionally, the way the output file is written can be adjusted through a few other options:

‘`-movflags empty_moov`’

  Write an initial moov atom directly at the start of the file, without describing any samples in it. Generally, an mdat/moov pair is written at the start of the file, as a normal MOV/MP4 file, containing only a short portion of the file. With this option set, there is no initial mdat atom, and the moov atom only describes the tracks but has a zero duration.

  Files written with this option set do not work in QuickTime. This option is implicitly set when writing ismv (Smooth Streaming) files.

‘`-movflags separate_moof`’

  Write a separate moof (movie fragment) atom for each track. Normally, packets for all tracks are written in a moof atom (which is slightly more efficient), but with this option set, the muxer writes one moof/mdat pair for each track, making it easier to separate tracks.

  This option is implicitly set when writing ismv (Smooth Streaming) files.

Smooth Streaming content can be pushed in real time to a publishing point on IIS with this muxer. Example:

    ffmpeg -re <normal input/transcoding options> -movflags isml+frag_keyframe -f ismv http://server/publishingpoint.isml/Streams(Encoder1)

## 9.7 mpegts

MPEG transport stream muxer.

This muxer implements ISO 13818-1 and part of ETSI EN 300 468.

The muxer options are:

‘`-mpegts_original_network_id number`’

  Set the original_network_id (default 0x0001). This is unique identifier of a network in DVB. Its main use is in the unique identification of a service through the path Original_Network_ID, Transport_Stream_ID.

‘`-mpegts_transport_stream_id number`’

  Set the transport_stream_id (default 0x0001). This identifies a transponder in DVB.

‘`-mpegts_service_id number`’

  Set the service_id (default 0x0001) also known as program in DVB.

‘`-mpegts_pmt_start_pid number`’

  Set the first PID for PMT (default 0x1000, max 0x1f00).

‘`-mpegts_start_pid number`’

  Set the first PID for data packets (default 0x0100, max 0x0f00).

The recognized metadata settings in mpegts muxer are `service_provider` and `service_name`. If they are not set the default for `service_provider` is "FFmpeg" and the default for `service_name` is "Service01".

    ffmpeg -i file.mpg -c copy \
         -mpegts_original_network_id 0x1122 \
         -mpegts_transport_stream_id 0x3344 \
         -mpegts_service_id 0x5566 \
         -mpegts_pmt_start_pid 0x1500 \
         -mpegts_start_pid 0x150 \
         -metadata service_provider="Some provider" \
         -metadata service_name="Some Channel" \
         -y out.ts

## 9.8 null

Null muxer.

This muxer does not generate any output file, it is mainly useful for testing or benchmarking purposes.

For example to benchmark decoding with `ffmpeg` you can use the command:

    ffmpeg -benchmark -i INPUT -f null out.null

Note that the above command does not read or write the ‘`out.null`’ file, but specifying the output file is required by the `ffmpeg` syntax.

Alternatively you can write the command as:

    ffmpeg -benchmark -i INPUT -f null -

## 9.9 matroska

Matroska container muxer.

This muxer implements the matroska and webm container specs.

The recognized metadata settings in this muxer are:

‘`title=title name`’

  Name provided to a single track

‘`language=language name`’

  Specifies the language of the track in the Matroska languages form

‘`stereo_mode=mode`’

  Stereo 3D video layout of two views in a single video track

  ‘`mono`’

    video is not stereo

  ‘`left_right`’

    Both views are arranged side by side, Left-eye view is on the left

  ‘`bottom_top`’

    Both views are arranged in top-bottom orientation, Left-eye view is at bottom

  ‘`top_bottom`’

    Both views are arranged in top-bottom orientation, Left-eye view is on top

  ‘`checkerboard_rl`’

    Each view is arranged in a checkerboard interleaved pattern, Left-eye view being first

  ‘`checkerboard_lr`’

    Each view is arranged in a checkerboard interleaved pattern, Right-eye view being first

  ‘`row_interleaved_rl`’

    Each view is constituted by a row based interleaving, Right-eye view is first row

  ‘`row_interleaved_lr`’

    Each view is constituted by a row based interleaving, Left-eye view is first row

  ‘`col_interleaved_rl`’

    Both views are arranged in a column based interleaving manner, Right-eye view is first column

  ‘`col_interleaved_lr`’

    Both views are arranged in a column based interleaving manner, Left-eye view is first column

  ‘`anaglyph_cyan_red`’

    All frames are in anaglyph format viewable through red-cyan filters

  ‘`right_left`’

    Both views are arranged side by side, Right-eye view is on the left

  ‘`anaglyph_green_magenta`’

    All frames are in anaglyph format viewable through green-magenta filters

  ‘`block_lr`’

    Both eyes laced in one Block, Left-eye view is first

  ‘`block_rl`’

    Both eyes laced in one Block, Right-eye view is first

For example a 3D WebM clip can be created using the following command line:

    ffmpeg -i sample_left_right_clip.mpg -an -c:v libvpx -metadata stereo_mode=left_right -y stereo_clip.webm

## 9.10 segment

Basic stream segmenter.

The segmenter muxer outputs streams to a number of separate files of nearly fixed duration. Output filename pattern can be set in a fashion similar to image2.

Every segment starts with a video keyframe, if a video stream is present. The segment muxer works best with a single constant frame rate video.

Optionally it can generate a flat list of the created segments, one segment per line.

‘`segment_format format`’

  Override the inner container format, by default it is guessed by the filename extension.

‘`segment_time t`’

  Set segment duration to t seconds.

‘`segment_list name`’

  Generate also a listfile named name.

‘`segment_list_size size`’

  Overwrite the listfile once it reaches size entries.

‘`segment_wrap limit`’

  Wrap around segment index once it reaches limit.

    ffmpeg -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut

## 9.11 mp3

The MP3 muxer writes a raw MP3 stream with an ID3v2 header at the beginning and optionally an ID3v1 tag at the end. ID3v2.3 and ID3v2.4 are supported, the `id3v2_version` option controls which one is used. The legacy ID3v1 tag is not written by default, but may be enabled with the `write_id3v1` option.

For seekable output the muxer also writes a Xing frame at the beginning, which contains the number of frames in the file. It is useful for computing duration of VBR files.

The muxer supports writing ID3v2 attached pictures (APIC frames). The pictures are supplied to the muxer in form of a video stream with a single packet. There can be any number of those streams, each will correspond to a single APIC frame. The stream metadata tags title and comment map to APIC description and picture type respectively. See http://id3.org/id3v2.4.0-frames for allowed picture types.

Note that the APIC frames must be written at the beginning, so the muxer will buffer the audio frames until it gets all the pictures. It is therefore advised to provide the pictures as soon as possible to avoid excessive buffering.

Examples:

Write an mp3 with an ID3v2.3 header and an ID3v1 footer:

    ffmpeg -i INPUT -id3v2_version 3 -write_id3v1 1 out.mp3

Attach a picture to an mp3:

    ffmpeg -i input.mp3 -i cover.png -c copy -metadata:s:v title="Album cover"
    -metadata:s:v comment="Cover (Front)" out.mp3

# 10. Input Devices

Input devices are configured elements in FFmpeg which allow to access the data coming from a multimedia device attached to your system.

When you configure your FFmpeg build, all the supported input devices are enabled by default. You can list all available ones using the configure option "–list-indevs".

You can disable all the input devices using the configure option "–disable-indevs", and selectively enable an input device using the option "–enable-indev=INDEV", or you can disable a particular input device using the option "–disable-indev=INDEV".

The option "-formats" of the ff* tools will display the list of supported input devices (amongst the demuxers).

A description of the currently available input devices follows.

## 10.1 alsa

ALSA (Advanced Linux Sound Architecture) input device.

To enable this input device during configuration you need libasound installed on your system.

This device allows capturing from an ALSA device. The name of the device to capture has to be an ALSA card identifier.

An ALSA identifier has the syntax:

    hw:CARD[,DEV[,SUBDEV]]

where the DEV and SUBDEV components are optional.

The three arguments (in order: CARD,DEV,SUBDEV) specify card number or identifier, device number and subdevice number (-1 means any).

To see the list of cards currently recognized by your system check the files ‘`/proc/asound/cards`’ and ‘`/proc/asound/devices`’.

For example to capture with `ffmpeg` from an ALSA device with card id 0, you may run the command:

    ffmpeg -f alsa -i hw:0 alsaout.wav

For more information see: http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html

## 10.2 bktr

BSD video input device.

## 10.3 dshow

Windows DirectShow input device.

DirectShow support is enabled when FFmpeg is built with the mingw-w64 project. Currently only audio and video devices are supported.

Multiple devices may be opened as separate inputs, but they may also be opened on the same input, which should improve synchronism between them.

The input name should be in the format:

    TYPE=NAME[:TYPE=NAME]

where TYPE can be either audio or video, and NAME is the device’s name.

### 10.3.1 Options

If no options are specified, the device’s defaults are used. If the device does not support the requested options, it will fail to open.

‘`video_size`’

  Set the video size in the captured video.

‘`framerate`’

  Set the framerate in the captured video.

‘`sample_rate`’

  Set the sample rate (in Hz) of the captured audio.

‘`sample_size`’

  Set the sample size (in bits) of the captured audio.

‘`channels`’

  Set the number of channels in the captured audio.

‘`list_devices`’

  If set to ‘`true`’, print a list of devices and exit.

‘`list_options`’

  If set to ‘`true`’, print a list of selected device’s options and exit.

‘`video_device_number`’

  Set video device number for devices with same name (starts at 0, defaults to 0).

‘`audio_device_number`’

  Set audio device number for devices with same name (starts at 0, defaults to 0).

### 10.3.2 Examples

- Print the list of DirectShow supported devices and exit:

      $ ffmpeg -list_devices true -f dshow -i dummy

- Open video device Camera:

      $ ffmpeg -f dshow -i video="Camera"

- Open second video device with name Camera:

      $ ffmpeg -f dshow -video_device_number 1 -i video="Camera"

- Open video device Camera and audio device Microphone:

      $ ffmpeg -f dshow -i video="Camera":audio="Microphone"

- Print the list of supported options in selected device and exit:

      $ ffmpeg -list_options true -f dshow -i video="Camera"

## 10.4 dv1394

Linux DV 1394 input device.

## 10.5 fbdev

Linux framebuffer input device.

The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console. It is accessed through a file device node, usually ‘`/dev/fb0`’.

For more detailed information read the file Documentation/fb/framebuffer.txt included in the Linux source tree.

To record from the framebuffer device ‘`/dev/fb0`’ with `ffmpeg`:

    ffmpeg -f fbdev -r 10 -i /dev/fb0 out.avi

You can take a single screenshot image with the command:

    ffmpeg -f fbdev -frames:v 1 -r 1 -i /dev/fb0 screenshot.jpeg

See also http://linux-fbdev.sourceforge.net/, and fbset(1).

## 10.6 jack

JACK input device.

To enable this input device during configuration you need libjack installed on your system.

A JACK input device creates one or more JACK writable clients, one for each audio channel, with name client_name:input_N, where client_name is the name provided by the application, and N is a number which identifies the channel. Each writable client will send the acquired data to the FFmpeg input device.

Once you have created one or more JACK readable clients, you need to connect them to one or more JACK writable clients.

To connect or disconnect JACK clients you can use the `jack_connect` and `jack_disconnect` programs, or do it through a graphical interface, for example with `qjackctl`.

To list the JACK clients and their properties you can invoke the command `jack_lsp`.

Follows an example which shows how to capture a JACK readable client with `ffmpeg`.

    # Create a JACK writable client with name "ffmpeg".
    $ ffmpeg -f jack -i ffmpeg -y out.wav

    # Start the sample jack_metro readable client.
    $ jack_metro -b 120 -d 0.2 -f 4000

    # List the current JACK clients.
    $ jack_lsp -c
    system:capture_1
    system:capture_2
    system:playback_1
    system:playback_2
    ffmpeg:input_1
    metro:120_bpm

    # Connect metro to the ffmpeg writable client.
    $ jack_connect metro:120_bpm ffmpeg:input_1

For more information read: http://jackaudio.org/

## 10.7 lavfi

Libavfilter input virtual device.

This input device reads data from the open output pads of a libavfilter filtergraph.

For each filtergraph open output, the input device will create a corresponding stream which is mapped to the generated output. Currently only video data is supported. The filtergraph is specified through the option ‘`graph`’.

### 10.7.1 Options

‘`graph`’

  Specify the filtergraph to use as input. Each video open output must be labelled by a unique string of the form "outN", where N is a number starting from 0 corresponding to the mapped input stream generated by the device. The first unlabelled output is automatically assigned to the "out0" label, but all the others need to be specified explicitly.

  If not specified defaults to the filename specified for the input device.

### 10.7.2 Examples

- Create a color video stream and play it back with `ffplay`:

      ffplay -f lavfi -graph "color=pink [out0]" dummy

- As the previous example, but use filename for specifying the graph description, and omit the "out0" label:

      ffplay -f lavfi color=pink

- Create three different video test filtered sources and play them:

      ffplay -f lavfi -graph "testsrc [out0]; testsrc,hflip [out1]; testsrc,negate [out2]" test3

- Read an audio stream from a file using the amovie source and play it back with `ffplay`:

      ffplay -f lavfi "amovie=test.wav"

- Read an audio stream and a video stream and play it back with `ffplay`:

      ffplay -f lavfi "movie=test.avi[out0];amovie=test.wav[out1]"

## 10.8 libdc1394

IIDC1394 input device, based on libdc1394 and libraw1394.

## 10.9 openal

The OpenAL input device provides audio capture on all systems with a working OpenAL 1.1 implementation.

To enable this input device during configuration, you need OpenAL headers and libraries installed on your system, and need to configure FFmpeg with `--enable-openal`.

OpenAL headers and libraries should be provided as part of your OpenAL implementation, or as an additional download (an SDK). Depending on your installation you may need to specify additional flags via the `--extra-cflags` and `--extra-ldflags` for allowing the build system to locate the OpenAL headers and libraries.

An incomplete list of OpenAL implementations follows:

Creative

  The official Windows implementation, providing hardware acceleration with supported devices and software fallback. See http://openal.org/.

OpenAL Soft

  Portable, open source (LGPL) software implementation. Includes backends for the most common sound APIs on the Windows, Linux, Solaris, and BSD operating systems. See http://kcat.strangesoft.net/openal.html.

Apple

  OpenAL is part of Core Audio, the official Mac OS X Audio interface. See http://developer.apple.com/technologies/mac/audio-and-video.html

This device allows to capture from an audio input device handled through OpenAL.

You need to specify the name of the device to capture in the provided filename. If the empty string is provided, the device will automatically select the default device. You can get the list of the supported devices by using the option list_devices.

### 10.9.1 Options

‘`channels`’

  Set the number of channels in the captured audio. Only the values ‘`1`’ (monaural) and ‘`2`’ (stereo) are currently supported. Defaults to ‘`2`’.

‘`sample_size`’

  Set the sample size (in bits) of the captured audio. Only the values ‘`8`’ and ‘`16`’ are currently supported. Defaults to ‘`16`’.

‘`sample_rate`’

  Set the sample rate (in Hz) of the captured audio. Defaults to ‘`44.1k`’.

‘`list_devices`’

  If set to ‘`true`’, print a list of devices and exit. Defaults to ‘`false`’.

### 10.9.2 Examples

Print the list of OpenAL supported devices and exit:

    $ ffmpeg -list_devices true -f openal -i dummy out.ogg

Capture from the OpenAL device ‘`DR-BT101 via PulseAudio`’:

    $ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out.ogg

Capture from the default device (note the empty string ” as filename):

    $ ffmpeg -f openal -i '' out.ogg

Capture from two devices simultaneously, writing to two different files, within the same `ffmpeg` command:

    $ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out1.ogg -f openal -i 'ALSA Default' out2.ogg

Note: not all OpenAL implementations support multiple simultaneous capture - try the latest OpenAL Soft if the above does not work.

## 10.10 oss

Open Sound System input device.

The filename to provide to the input device is the device node representing the OSS input device, and is usually set to ‘`/dev/dsp`’.

For example to grab from ‘`/dev/dsp`’ using `ffmpeg` use the command:

    ffmpeg -f oss -i /dev/dsp /tmp/oss.wav

For more information about OSS see: http://manuals.opensound.com/usersguide/dsp.html

## 10.11 pulse

pulseaudio input device.

To enable this input device during configuration you need libpulse-simple installed in your system.

The filename to provide to the input device is a source device or the string "default"

To list the pulse source devices and their properties you can invoke the command `pactl list sources`.

    ffmpeg -f pulse -i default /tmp/pulse.wav

### 10.11.1 server AVOption

The syntax is:

    -server server name

Connects to a specific server.

### 10.11.2 name AVOption

The syntax is:

    -name application name

Specify the application name pulse will use when showing active clients, by default it is the LIBAVFORMAT_IDENT string

### 10.11.3 stream_name AVOption

The syntax is:

    -stream_name stream name

Specify the stream name pulse will use when showing active streams, by default it is "record"

### 10.11.4 sample_rate AVOption

The syntax is:

    -sample_rate samplerate

Specify the samplerate in Hz, by default 48kHz is used.

### 10.11.5 channels AVOption

The syntax is:

    -channels N

Specify the channels in use, by default 2 (stereo) is set.

### 10.11.6 frame_size AVOption

The syntax is:

    -frame_size bytes

Specify the number of byte per frame, by default it is set to 1024.

### 10.11.7 fragment_size AVOption

The syntax is:

    -fragment_size bytes

Specify the minimal buffering fragment in pulseaudio, it will affect the audio latency. By default it is unset.

## 10.12 sndio

sndio input device.

To enable this input device during configuration you need libsndio installed on your system.

The filename to provide to the input device is the device node representing the sndio input device, and is usually set to ‘`/dev/audio0`’.

For example to grab from ‘`/dev/audio0`’ using `ffmpeg` use the command:

    ffmpeg -f sndio -i /dev/audio0 /tmp/oss.wav

## 10.13 video4linux2

Video4Linux2 input video device.

The name of the device to grab is a file device node, usually Linux systems tend to automatically create such nodes when the device (e.g. an USB webcam) is plugged into the system, and has a name of the kind ‘`/dev/videoN`’, where N is a number associated to the device.

Video4Linux2 devices usually support a limited set of widthxheight sizes and framerates. You can check which are supported using `-list_formats all` for Video4Linux2 devices.

Some usage examples of the video4linux2 devices with ffmpeg and ffplay:

The time base for the timestamps is 1 microsecond. Depending on the kernel version and configuration, the timestamps may be derived from the real time clock (origin at the Unix Epoch) or the monotonic clock (origin usually at boot time, unaffected by NTP or manual changes to the clock). The ‘`-timestamps abs`’ or ‘`-ts abs`’ option can be used to force conversion into the real time clock.

Note that if FFmpeg is build with v4l-utils support ("–enable-libv4l2" option), it will always be used.

    # Grab and show the input of a video4linux2 device.
    ffplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0

    # Grab and record the input of a video4linux2 device, leave the
    framerate and size as previously set.
    ffmpeg -f video4linux2 -input_format mjpeg -i /dev/video0 out.mpeg

"v4l" and "v4l2" can be used as aliases for the respective "video4linux" and "video4linux2".

## 10.14 vfwcap

VfW (Video for Windows) capture input device.

The filename passed as input is the capture driver number, ranging from 0 to 9. You may use "list" as filename to print a list of drivers. Any other filename will be interpreted as device number 0.

## 10.15 x11grab

X11 video input device.

This device allows to capture a region of an X11 display.

The filename passed as input has the syntax:

    [hostname]:display_number.screen_number[+x_offset,y_offset]

hostname:display_number.screen_number specifies the X11 display name of the screen to grab from. hostname can be omitted, and defaults to "localhost". The environment variable `DISPLAY` contains the default display name.

x_offset and y_offset specify the offsets of the grabbed area with respect to the top-left border of the X11 screen. They default to 0.

Check the X11 documentation (e.g. man X) for more detailed information.

Use the `dpyinfo` program for getting basic information about the properties of your X11 display (e.g. grep for "name" or "dimensions").

For example to grab from ‘`:0.0`’ using `ffmpeg`:

    ffmpeg -f x11grab -r 25 -s cif -i :0.0 out.mpg

    # Grab at position 10,20.
    ffmpeg -f x11grab -r 25 -s cif -i :0.0+10,20 out.mpg

### 10.15.1 follow_mouse AVOption

The syntax is:

    -follow_mouse centered|PIXELS

When it is specified with "centered", the grabbing region follows the mouse pointer and keeps the pointer at the center of region; otherwise, the region follows only when the mouse pointer reaches within PIXELS (greater than zero) to the edge of region.

For example:

    ffmpeg -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg

    # Follows only when the mouse pointer reaches within 100 pixels to edge
    ffmpeg -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg

### 10.15.2 show_region AVOption

The syntax is:

    -show_region 1

If show_region AVOption is specified with 1, then the grabbing region will be indicated on screen. With this option, it’s easy to know what is being grabbed if only a portion of the screen is grabbed.

For example:

    ffmpeg -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg

    # With follow_mouse
    ffmpeg -f x11grab -follow_mouse centered -show_region 1  -r 25 -s cif -i :0.0 out.mpg

# 11. Output Devices

Output devices are configured elements in FFmpeg which allow to write multimedia data to an output device attached to your system.

When you configure your FFmpeg build, all the supported output devices are enabled by default. You can list all available ones using the configure option "–list-outdevs".

You can disable all the output devices using the configure option "–disable-outdevs", and selectively enable an output device using the option "–enable-outdev=OUTDEV", or you can disable a particular input device using the option "–disable-outdev=OUTDEV".

The option "-formats" of the ff* tools will display the list of enabled output devices (amongst the muxers).

A description of the currently available output devices follows.

## 11.1 alsa

ALSA (Advanced Linux Sound Architecture) output device.

## 11.2 oss

OSS (Open Sound System) output device.

## 11.3 sdl

SDL (Simple DirectMedia Layer) output device.

This output devices allows to show a video stream in an SDL window. Only one SDL window is allowed per application, so you can have only one instance of this output device in an application.

To enable this output device you need libsdl installed on your system when configuring your build.

For more information about SDL, check: http://www.libsdl.org/

### 11.3.1 Options

‘`window_title`’

  Set the SDL window title, if not specified default to the filename specified for the output device.

‘`icon_title`’

  Set the name of the iconified SDL window, if not specified it is set to the same value of window_title.

‘`window_size`’

  Set the SDL window size, can be a string of the form widthxheight or a video size abbreviation. If not specified it defaults to the size of the input video.

### 11.3.2 Examples

The following command shows the `ffmpeg` output is an SDL window, forcing its size to the qcif format:

    ffmpeg -i INPUT -vcodec rawvideo -pix_fmt yuv420p -window_size qcif -f sdl "SDL output"

## 11.4 sndio

sndio audio output device.

# 12. Protocols

Protocols are configured elements in FFmpeg which allow to access resources which require the use of a particular protocol.

When you configure your FFmpeg build, all the supported protocols are enabled by default. You can list all available ones using the configure option "–list-protocols".

You can disable all the protocols using the configure option "–disable-protocols", and selectively enable a protocol using the option "–enable-protocol=PROTOCOL", or you can disable a particular protocol using the option "–disable-protocol=PROTOCOL".

The option "-protocols" of the ff* tools will display the list of supported protocols.

A description of the currently available protocols follows.

## 12.1 bluray

Read BluRay playlist.

The accepted options are:

‘`angle`’

  BluRay angle

‘`chapter`’

  Start chapter (1...N)

‘`playlist`’

  Playlist to read (BDMV/PLAYLIST/?????.mpls)

Examples:

Read longest playlist from BluRay mounted to /mnt/bluray:

    bluray:/mnt/bluray

Read angle 2 of playlist 4 from BluRay mounted to /mnt/bluray, start from chapter 2:

    -playlist 4 -angle 2 -chapter 2 bluray:/mnt/bluray

## 12.2 concat

Physical concatenation protocol.

Allow to read and seek from many resource in sequence as if they were a unique resource.

A URL accepted by this protocol has the syntax:

    concat:URL1|URL2|...|URLN

where URL1, URL2, ..., URLN are the urls of the resource to be concatenated, each one possibly specifying a distinct protocol.

For example to read a sequence of files ‘`split1.mpeg`’, ‘`split2.mpeg`’, ‘`split3.mpeg`’ with `ffplay` use the command:

    ffplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg

Note that you may need to escape the character "|" which is special for many shells.

## 12.3 file

File access protocol.

Allow to read from or read to a file.

For example to read from a file ‘`input.mpeg`’ with `ffmpeg` use the command:

    ffmpeg -i file:input.mpeg output.mpeg

The ff* tools default to the file protocol, that is a resource specified with the name "FILE.mpeg" is interpreted as the URL "file:FILE.mpeg".

## 12.4 gopher

Gopher protocol.

## 12.5 hls

Read Apple HTTP Live Streaming compliant segmented stream as a uniform one. The M3U8 playlists describing the segments can be remote HTTP resources or local files, accessed using the standard file protocol. The nested protocol is declared by specifying "+proto" after the hls URI scheme name, where proto is either "file" or "http".

    hls+http://host/path/to/remote/resource.m3u8
    hls+file://path/to/local/resource.m3u8

Using this protocol is discouraged - the hls demuxer should work just as well (if not, please report the issues) and is more complete. To use the hls demuxer instead, simply use the direct URLs to the m3u8 files.

## 12.6 http

HTTP (Hyper Text Transfer Protocol).

## 12.7 mmst

MMS (Microsoft Media Server) protocol over TCP.

## 12.8 mmsh

MMS (Microsoft Media Server) protocol over HTTP.

The required syntax is:

    mmsh://server[:port][/app][/playpath]

## 12.9 md5

MD5 output protocol.

Computes the MD5 hash of the data to be written, and on close writes this to the designated output or stdout if none is specified. It can be used to test muxers without writing an actual file.

Some examples follow.

    # Write the MD5 hash of the encoded AVI file to the file output.avi.md5.
    ffmpeg -i input.flv -f avi -y md5:output.avi.md5

    # Write the MD5 hash of the encoded AVI file to stdout.
    ffmpeg -i input.flv -f avi -y md5:

Note that some formats (typically MOV) require the output protocol to be seekable, so they will fail with the MD5 output protocol.

## 12.10 pipe

UNIX pipe access protocol.

Allow to read and write from UNIX pipes.

The accepted syntax is:

    pipe:[number]

number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading.

For example to read from stdin with `ffmpeg`:

    cat test.wav | ffmpeg -i pipe:0
    # ...this is the same as...
    cat test.wav | ffmpeg -i pipe:

For writing to stdout with `ffmpeg`:

    ffmpeg -i test.wav -f avi pipe:1 | cat > test.avi
    # ...this is the same as...
    ffmpeg -i test.wav -f avi pipe: | cat > test.avi

Note that some formats (typically MOV), require the output protocol to be seekable, so they will fail with the pipe output protocol.

## 12.11 rtmp

Real-Time Messaging Protocol.

The Real-Time Messaging Protocol (RTMP) is used for streaming multimedia content across a TCP/IP network.

The required syntax is:

    rtmp://server[:port][/app][/playpath]

The accepted parameters are:

‘`server`’

  The address of the RTMP server.

‘`port`’

  The number of the TCP port to use (by default is 1935).

‘`app`’

  It is the name of the application to access. It usually corresponds to the path where the application is installed on the RTMP server (e.g. ‘`/ondemand/`’, ‘`/flash/live/`’, etc.).

‘`playpath`’

  It is the path or name of the resource to play with reference to the application specified in app, may be prefixed by "mp4:".

For example to read with `ffplay` a multimedia resource named "sample" from the application "vod" from an RTMP server "myserver":

    ffplay rtmp://myserver/vod/sample

## 12.12 rtmp, rtmpe, rtmps, rtmpt, rtmpte

Real-Time Messaging Protocol and its variants supported through librtmp.

Requires the presence of the librtmp headers and library during configuration. You need to explicitly configure the build with "–enable-librtmp". If enabled this will replace the native RTMP protocol.

This protocol provides most client functions and a few server functions needed to support RTMP, RTMP tunneled in HTTP (RTMPT), encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled variants of these encrypted types (RTMPTE, RTMPTS).

The required syntax is:

    rtmp_proto://server[:port][/app][/playpath] options

where rtmp_proto is one of the strings "rtmp", "rtmpt", "rtmpe", "rtmps", "rtmpte", "rtmpts" corresponding to each RTMP variant, and server, port, app and playpath have the same meaning as specified for the RTMP native protocol. options contains a list of space-separated options of the form key=val.

See the librtmp manual page (man 3 librtmp) for more information.

For example, to stream a file in real-time to an RTMP server using `ffmpeg`:

    ffmpeg -re -i myfile -f flv rtmp://myserver/live/mystream

To play the same stream using `ffplay`:

    ffplay "rtmp://myserver/live/mystream live=1"

## 12.13 rtp

Real-Time Protocol.

## 12.14 rtsp

RTSP is not technically a protocol handler in libavformat, it is a demuxer and muxer. The demuxer supports both normal RTSP (with data transferred over RTP; this is used by e.g. Apple and Microsoft) and Real-RTSP (with data transferred over RDT).

The muxer can be used to send a stream using RTSP ANNOUNCE to a server supporting it (currently Darwin Streaming Server and Mischa Spiegelmock’s RTSP server).

The required syntax for a RTSP url is:

    rtsp://hostname[:port]/path

The following options (set on the `ffmpeg`/`ffplay` command line, or set in code via `AVOption`s or in `avformat_open_input`), are supported:

Flags for `rtsp_transport`:

‘`udp`’

  Use UDP as lower transport protocol.

‘`tcp`’

  Use TCP (interleaving within the RTSP control channel) as lower transport protocol.

‘`udp_multicast`’

  Use UDP multicast as lower transport protocol.

‘`http`’

  Use HTTP tunneling as lower transport protocol, which is useful for passing proxies.

Multiple lower transport protocols may be specified, in that case they are tried one at a time (if the setup of one fails, the next one is tried). For the muxer, only the `tcp` and `udp` options are supported.

Flags for `rtsp_flags`:

‘`filter_src`’

  Accept packets only from negotiated peer address and port.

When receiving data over UDP, the demuxer tries to reorder received packets (since they may arrive out of order, or packets may get lost totally). This can be disabled by setting the maximum demuxing delay to zero (via the `max_delay` field of AVFormatContext).

When watching multi-bitrate Real-RTSP streams with `ffplay`, the streams to display can be chosen with `-vst` n and `-ast` n for video and audio respectively, and can be switched on the fly by pressing `v` and `a`.

Example command lines:

To watch a stream over UDP, with a max reordering delay of 0.5 seconds:

    ffplay -max_delay 500000 -rtsp_transport udp rtsp://server/video.mp4

To watch a stream tunneled over HTTP:

    ffplay -rtsp_transport http rtsp://server/video.mp4

To send a stream in realtime to a RTSP server, for others to watch:

    ffmpeg -re -i input -f rtsp -muxdelay 0.1 rtsp://server/live.sdp

## 12.15 sap

Session Announcement Protocol (RFC 2974). This is not technically a protocol handler in libavformat, it is a muxer and demuxer. It is used for signalling of RTP streams, by announcing the SDP for the streams regularly on a separate port.

### 12.15.1 Muxer

The syntax for a SAP url given to the muxer is:

    sap://destination[:port][?options]

The RTP packets are sent to destination on port port, or to port 5004 if no port is specified. options is a `&`-separated list. The following options are supported:

‘`announce_addr=address`’

  Specify the destination IP address for sending the announcements to. If omitted, the announcements are sent to the commonly used SAP announcement multicast address 224.2.127.254 (sap.mcast.net), or ff0e::2:7ffe if destination is an IPv6 address.

‘`announce_port=port`’

  Specify the port to send the announcements on, defaults to 9875 if not specified.

‘`ttl=ttl`’

  Specify the time to live value for the announcements and RTP packets, defaults to 255.

‘`same_port=0|1`’

  If set to 1, send all RTP streams on the same port pair. If zero (the default), all streams are sent on unique ports, with each stream on a port 2 numbers higher than the previous. VLC/Live555 requires this to be set to 1, to be able to receive the stream. The RTP stack in libavformat for receiving requires all streams to be sent on unique ports.

Example command lines follow.

To broadcast a stream on the local subnet, for watching in VLC:

    ffmpeg -re -i input -f sap sap://224.0.0.255?same_port=1

Similarly, for watching in `ffplay`:

    ffmpeg -re -i input -f sap sap://224.0.0.255

And for watching in `ffplay`, over IPv6:

    ffmpeg -re -i input -f sap sap://[ff0e::1:2:3:4]

### 12.15.2 Demuxer

The syntax for a SAP url given to the demuxer is:

    sap://[address][:port]

address is the multicast address to listen for announcements on, if omitted, the default 224.2.127.254 (sap.mcast.net) is used. port is the port that is listened on, 9875 if omitted.

The demuxers listens for announcements on the given address and port. Once an announcement is received, it tries to receive that particular stream.

Example command lines follow.

To play back the first stream announced on the normal SAP multicast address:

    ffplay sap://

To play back the first stream announced on one the default IPv6 SAP multicast address:

    ffplay sap://[ff0e::2:7ffe]

## 12.16 tcp

Trasmission Control Protocol.

The required syntax for a TCP url is:

    tcp://hostname:port[?options]

‘`listen`’

  Listen for an incoming connection

      ffmpeg -i input -f format tcp://hostname:port?listen
      ffplay tcp://hostname:port

## 12.17 udp

User Datagram Protocol.

The required syntax for a UDP url is:

    udp://hostname:port[?options]

options contains a list of &-seperated options of the form key=val. Follow the list of supported options.

‘`buffer_size=size`’

  set the UDP buffer size in bytes

‘`localport=port`’

  override the local UDP port to bind with

‘`localaddr=addr`’

  Choose the local IP address. This is useful e.g. if sending multicast and the host has multiple interfaces, where the user can choose which interface to send on by specifying the IP address of that interface.

‘`pkt_size=size`’

  set the size in bytes of UDP packets

‘`reuse=1|0`’

  explicitly allow or disallow reusing UDP sockets

‘`ttl=ttl`’

  set the time to live value (for multicast only)

‘`connect=1|0`’

  Initialize the UDP socket with `connect()`. In this case, the destination address can’t be changed with ff_udp_set_remote_url later. If the destination address isn’t known at the start, this option can be specified in ff_udp_set_remote_url, too. This allows finding out the source address for the packets with getsockname, and makes writes return with AVERROR(ECONNREFUSED) if "destination unreachable" is received. For receiving, this gives the benefit of only receiving packets from the specified peer address/port.

Some usage examples of the udp protocol with `ffmpeg` follow.

To stream over UDP to a remote endpoint:

    ffmpeg -i input -f format udp://hostname:port

To stream in mpegts format over UDP using 188 sized UDP packets, using a large input buffer:

    ffmpeg -i input -f mpegts udp://hostname:port?pkt_size=188&buffer_size=65535

To receive over UDP from a remote endpoint:

    ffmpeg -i udp://[multicast-address]:port

# 13. Filtergraph description

A filtergraph is a directed graph of connected filters. It can contain cycles, and there can be multiple links between a pair of filters. Each link has one input pad on one side connecting it to one filter from which it takes its input, and one output pad on the other side connecting it to the one filter accepting its output.

Each filter in a filtergraph is an instance of a filter class registered in the application, which defines the features and the number of input and output pads of the filter.

A filter with no input pads is called a "source", a filter with no output pads is called a "sink".

## 13.1 Filtergraph syntax

A filtergraph can be represented using a textual representation, which is recognized by the ‘`-filter`’/‘`-vf`’ and ‘`-filter_complex`’ options in `ffmpeg` and ‘`-vf`’ in `ffplay`, and by the `avfilter_graph_parse()`/`avfilter_graph_parse2()` function defined in ‘`libavfilter/avfiltergraph.h`’.

A filterchain consists of a sequence of connected filters, each one connected to the previous one in the sequence. A filterchain is represented by a list of ","-separated filter descriptions.

A filtergraph consists of a sequence of filterchains. A sequence of filterchains is represented by a list of ";"-separated filterchain descriptions.

A filter is represented by a string of the form: [in_link_1]...[in_link_N]filter_name=arguments[out_link_1]...[out_link_M]

filter_name is the name of the filter class of which the described filter is an instance of, and has to be the name of one of the filter classes registered in the program. The name of the filter class is optionally followed by a string "=arguments".

arguments is a string which contains the parameters used to initialize the filter instance, and are described in the filter descriptions below.

The list of arguments can be quoted using the character "’" as initial and ending mark, and the character ’\’ for escaping the characters within the quoted text; otherwise the argument string is considered terminated when the next special character (belonging to the set "[]=;,") is encountered.

The name and arguments of the filter are optionally preceded and followed by a list of link labels. A link label allows to name a link and associate it to a filter output or input pad. The preceding labels in_link_1 ... in_link_N, are associated to the filter input pads, the following labels out_link_1 ... out_link_M, are associated to the output pads.

When two link labels with the same name are found in the filtergraph, a link between the corresponding input and output pad is created.

If an output pad is not labelled, it is linked by default to the first unlabelled input pad of the next filter in the filterchain. For example in the filterchain:

    nullsrc, split[L1], [L2]overlay, nullsink

the split filter instance has two output pads, and the overlay filter instance two input pads. The first output pad of split is labelled "L1", the first input pad of overlay is labelled "L2", and the second output pad of split is linked to the second input pad of overlay, which are both unlabelled.

In a complete filterchain all the unlabelled filter input and output pads must be connected. A filtergraph is considered valid if all the filter input and output pads of all the filterchains are connected.

Libavfilter will automatically insert scale filters where format conversion is required. It is possible to specify swscale flags for those automatically inserted scalers by prepending `sws_flags=flags;` to the filtergraph description.

Follows a BNF description for the filtergraph syntax:

    NAME             ::= sequence of alphanumeric characters and '_'
    LINKLABEL        ::= "[" NAME "]"
    LINKLABELS       ::= LINKLABEL [LINKLABELS]
    FILTER_ARGUMENTS ::= sequence of chars (eventually quoted)
    FILTER           ::= [LINKNAMES] NAME ["=" ARGUMENTS] [LINKNAMES]
    FILTERCHAIN      ::= FILTER [,FILTERCHAIN]
    FILTERGRAPH      ::= [sws_flags=flags;] FILTERCHAIN [;FILTERGRAPH]

# 14. Audio Filters

When you configure your FFmpeg build, you can disable any of the existing filters using `--disable-filters`. The configure output will show the audio filters included in your build.

Below is a description of the currently available audio filters.

## 14.1 aconvert

Convert the input audio format to the specified formats.

The filter accepts a string of the form: "sample_format:channel_layout".

sample_format specifies the sample format, and can be a string or the corresponding numeric value defined in ‘`libavutil/samplefmt.h`’. Use ’p’ suffix for a planar sample format.

channel_layout specifies the channel layout, and can be a string or the corresponding number value defined in ‘`libavutil/audioconvert.h`’.

The special parameter "auto", signifies that the filter will automatically select the output format depending on the output filter.

Some examples follow.

- Convert input to float, planar, stereo:

      aconvert=fltp:stereo

- Convert input to unsigned 8-bit, automatically select out channel layout:

      aconvert=u8:auto

## 14.2 aformat

Convert the input audio to one of the specified formats. The framework will negotiate the most appropriate format to minimize conversions.

The filter accepts three lists of formats, separated by ":", in the form: "sample_formats:channel_layouts:packing_formats".

Elements in each list are separated by "," which has to be escaped in the filtergraph specification.

The special parameter "all", in place of a list of elements, signifies all supported formats.

Some examples follow:

    aformat=u8\\,s16:mono:packed

    aformat=s16:mono\\,stereo:all

## 14.3 amerge

Merge two audio streams into a single multi-channel stream.

This filter does not need any argument.

If the channel layouts of the inputs are disjoint, and therefore compatible, the channel layout of the output will be set accordingly and the channels will be reordered as necessary. If the channel layouts of the inputs are not disjoint, the output will have all the channels of the first input then all the channels of the second input, in that order, and the channel layout of the output will be the default value corresponding to the total number of channels.

For example, if the first input is in 2.1 (FL+FR+LF) and the second input is FC+BL+BR, then the output will be in 5.1, with the channels in the following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the first input, b1 is the first channel of the second input).

On the other hand, if both input are in stereo, the output channels will be in the default order: a1, a2, b1, b2, and the channel layout will be arbitrarily set to 4.0, which may or may not be the expected value.

Both inputs must have the same sample rate, format and packing.

If inputs do not have the same duration, the output will stop with the shortest.

Example: merge two mono files into a stereo stream:

    amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge

If you need to do multiple merges (for instance multiple mono audio streams in a single video media), you can do:

    ffmpeg -f lavfi -i "
    amovie=input.mkv:si=0 [a0];
    amovie=input.mkv:si=1 [a1];
    amovie=input.mkv:si=2 [a2];
    amovie=input.mkv:si=3 [a3];
    amovie=input.mkv:si=4 [a4];
    amovie=input.mkv:si=5 [a5];
    [a0][a1] amerge [x0];
    [x0][a2] amerge [x1];
    [x1][a3] amerge [x2];
    [x2][a4] amerge [x3];
    [x3][a5] amerge" -c:a pcm_s16le output.mkv

## 14.4 anull

Pass the audio source unchanged to the output.

## 14.5 aresample

Resample the input audio to the specified sample rate.

The filter accepts exactly one parameter, the output sample rate. If not specified then the filter will automatically convert between its input and output sample rates.

For example, to resample the input audio to 44100Hz:

    aresample=44100

## 14.6 ashowinfo

Show a line containing various information for each input audio frame. The input audio is not modified.

The shown line contains a sequence of key/value pairs of the form key:value.

A description of each shown parameter follows:

‘`n`’

  sequential number of the input frame, starting from 0

‘`pts`’

  presentation TimeStamp of the input frame, expressed as a number of time base units. The time base unit depends on the filter input pad, and is usually 1/sample_rate.

‘`pts_time`’

  presentation TimeStamp of the input frame, expressed as a number of seconds

‘`pos`’

  position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic audio)

‘`fmt`’

  sample format name

‘`chlayout`’

  channel layout description

‘`nb_samples`’

  number of samples (per each channel) contained in the filtered frame

‘`rate`’

  sample rate for the audio frame

‘`planar`’

  if the packing format is planar, 0 if packed

‘`checksum`’

  Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame

‘`plane_checksum`’

  Adler-32 checksum (printed in hexadecimal) for each input frame plane, expressed in the form "[c0 c1 c2 c3 c4 c5 c6 c7]"

## 14.7 asplit

Pass on the input audio to two outputs. Both outputs are identical to the input audio.

For example:

    [in] asplit[out0], showaudio[out1]

will create two separate outputs from the same input, one cropped and one padded.

## 14.8 astreamsync

Forward two audio streams and control the order the buffers are forwarded.

The argument to the filter is an expression deciding which stream should be forwarded next: if the result is negative, the first stream is forwarded; if the result is positive or zero, the second stream is forwarded. It can use the following variables:

b1 b2

  number of buffers forwarded so far on each stream

s1 s2

  number of samples forwarded so far on each stream

t1 t2

  current timestamp of each stream

The default value is `t1-t2`, which means to always forward the stream that has a smaller timestamp.

Example: stress-test `amerge` by randomly sending buffers on the wrong input, while avoiding too much of a desynchronization:

    amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
    [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
    [a2] [b2] amerge

## 14.9 earwax

Make audio easier to listen to on headphones.

This filter adds ‘cues’ to 44.1kHz stereo (i.e. audio CD format) audio so that when listened to on headphones the stereo image is moved from inside your head (standard for headphones) to outside and in front of the listener (standard for speakers).

Ported from SoX.

## 14.10 pan

Mix channels with specific gain levels. The filter accepts the output channel layout followed by a set of channels definitions.

This filter is also designed to remap efficiently the channels of an audio stream.

The filter accepts parameters of the form: "l:outdef:outdef:..."

‘`l`’

  output channel layout or number of channels

‘`outdef`’

  output channel specification, of the form: "out_name=[gain*]in_name[+[gain*]in_name...]"

‘`out_name`’

  output channel to define, either a channel name (FL, FR, etc.) or a channel number (c0, c1, etc.)

‘`gain`’

  multiplicative coefficient for the channel, 1 leaving the volume unchanged

‘`in_name`’

  input channel to use, see out_name for details; it is not possible to mix named and numbered input channels

If the ‘=’ in a channel specification is replaced by ‘<’, then the gains for that specification will be renormalized so that the total is 1, thus avoiding clipping noise.

### 14.10.1 Mixing examples

For example, if you want to down-mix from stereo to mono, but with a bigger factor for the left channel:

    pan=1:c0=0.9*c0+0.1*c1

A customized down-mix to stereo that works automatically for 3-, 4-, 5- and 7-channels surround:

    pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR

Note that `ffmpeg` integrates a default down-mix (and up-mix) system that should be preferred (see "-ac" option) unless you have very specific needs.

### 14.10.2 Remapping examples

The channel remapping will be effective if, and only if:

- gain coefficients are zeroes or ones,
- only one input per channel output,

If all these conditions are satisfied, the filter will notify the user ("Pure channel mapping detected"), and use an optimized and lossless method to do the remapping.

For example, if you have a 5.1 source and want a stereo audio stream by dropping the extra channels:

    pan="stereo: c0=FL : c1=FR"

Given the same source, you can also switch front left and front right channels and keep the input channel layout:

    pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"

If the input is a stereo audio stream, you can mute the front left channel (and still keep the stereo channel layout) with:

    pan="stereo:c1=c1"

Still with a stereo audio stream input, you can copy the right channel in both front left and right:

    pan="stereo: c0=FR : c1=FR"

## 14.11 silencedetect

Detect silence in an audio stream.

This filter logs a message when it detects that the input audio volume is less or equal to a noise tolerance value for a duration greater or equal to the minimum detected noise duration.

The printed times and duration are expressed in seconds.

‘`duration, d`’

  Set silence duration until notification (default is 2 seconds).

‘`noise, n`’

  Set noise tolerance. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default is -60dB, or 0.001.

Detect 5 seconds of silence with -50dB noise tolerance:

    silencedetect=n=-50dB:d=5

Complete example with `ffmpeg` to detect silence with 0.0001 noise tolerance in ‘`silence.mp3`’:

    ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -

## 14.12 volume

Adjust the input audio volume.

The filter accepts exactly one parameter vol, which expresses how the audio volume will be increased or decreased.

Output values are clipped to the maximum value.

If vol is expressed as a decimal number, the output audio volume is given by the relation:

    output_volume = vol * input_volume

If vol is expressed as a decimal number followed by the string "dB", the value represents the requested change in decibels of the input audio power, and the output audio volume is given by the relation:

    output_volume = 10^(vol/20) * input_volume

Otherwise vol is considered an expression and its evaluated value is used for computing the output audio volume according to the first relation.

Default value for vol is 1.0.

### 14.12.1 Examples

- Half the input audio volume:

      volume=0.5

  The above example is equivalent to:

      volume=1/2

- Decrease input audio power by 12 decibels:

      volume=-12dB

# 15. Audio Sources

Below is a description of the currently available audio sources.

## 15.1 abuffer

Buffer audio frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular through the interface defined in ‘`libavfilter/asrc_abuffer.h`’.

It accepts the following mandatory parameters: sample_rate:sample_fmt:channel_layout:packing

‘`sample_rate`’

  The sample rate of the incoming audio buffers.

‘`sample_fmt`’

  The sample format of the incoming audio buffers. Either a sample format name or its corresponging integer representation from the enum AVSampleFormat in ‘`libavutil/samplefmt.h`’

‘`channel_layout`’

  The channel layout of the incoming audio buffers. Either a channel layout name from channel_layout_map in ‘`libavutil/audioconvert.c`’ or its corresponding integer representation from the AV_CH_LAYOUT_* macros in ‘`libavutil/audioconvert.h`’

‘`packing`’

  Either "packed" or "planar", or their integer representation: 0 or 1 respectively.

For example:

    abuffer=44100:s16:stereo:planar

will instruct the source to accept planar 16bit signed stereo at 44100Hz. Since the sample format with name "s16" corresponds to the number 1 and the "stereo" channel layout corresponds to the value 0x3, this is equivalent to:

    abuffer=44100:1:0x3:1

## 15.2 aevalsrc

Generate an audio signal specified by an expression.

This source accepts in input one or more expressions (one for each channel), which are evaluated and used to generate a corresponding audio signal.

It accepts the syntax: exprs[::options]. exprs is a list of expressions separated by ":", one for each separate channel. The output channel layout depends on the number of provided expressions, up to 8 channels are supported.

options is an optional sequence of key=value pairs, separated by ":".

The description of the accepted options follows.

‘`duration, d`’

  Set the minimum duration of the sourced audio. See the function `av_parse_time()` for the accepted format. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame.

  If not specified, or the expressed duration is negative, the audio is supposed to be generated forever.

‘`nb_samples, n`’

  Set the number of samples per channel per each output frame, default to 1024.

‘`sample_rate, s`’

  Specify the sample rate, default to 44100.

Each expression in exprs can contain the following constants:

‘`n`’

  number of the evaluated sample, starting from 0

‘`t`’

  time of the evaluated sample expressed in seconds, starting from 0

‘`s`’

  sample rate

### 15.2.1 Examples

- Generate silence:

      aevalsrc=0

- Generate a sin signal with frequency of 440 Hz, set sample rate to 8000 Hz:

      aevalsrc="sin(440*2*PI*t)::s=8000"

- Generate white noise:

      aevalsrc="-2+random(0)"

- Generate an amplitude modulated signal:

      aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"

- Generate 2.5 Hz binaural beats on a 360 Hz carrier:

      aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"

## 15.3 amovie

Read an audio stream from a movie container.

It accepts the syntax: movie_name[:options] where movie_name is the name of the resource to read (not necessarily a file but also a device or a stream accessed through some protocol), and options is an optional sequence of key=value pairs, separated by ":".

The description of the accepted options follows.

‘`format_name, f`’

  Specify the format assumed for the movie to read, and can be either the name of a container or an input device. If not specified the format is guessed from movie_name or by probing.

‘`seek_point, sp`’

  Specify the seek point in seconds, the frames will be output starting from this seek point, the parameter is evaluated with `av_strtod` so the numerical value may be suffixed by an IS postfix. Default value is "0".

‘`stream_index, si`’

  Specify the index of the audio stream to read. If the value is -1, the best suited audio stream will be automatically selected. Default value is "-1".

## 15.4 anullsrc

Null audio source, return unprocessed audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools, or as the source for filters which ignore the input data (for example the sox synth filter).

It accepts an optional sequence of key=value pairs, separated by ":".

The description of the accepted options follows.

‘`sample_rate, s`’

  Specify the sample rate, and defaults to 44100.

‘`channel_layout, cl`’

  Specify the channel layout, and can be either an integer or a string representing a channel layout. The default value of channel_layout is "stereo".

  Check the channel_layout_map definition in ‘`libavcodec/audioconvert.c`’ for the mapping between strings and channel layout values.

‘`nb_samples, n`’

  Set the number of samples per requested frames.

Follow some examples:

    #  set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
    anullsrc=r=48000:cl=4

    # same as
    anullsrc=r=48000:cl=mono

# 16. Audio Sinks

Below is a description of the currently available audio sinks.

## 16.1 abuffersink

Buffer audio frames, and make them available to the end of filter chain.

This sink is mainly intended for programmatic use, in particular through the interface defined in ‘`libavfilter/buffersink.h`’.

It requires a pointer to an AVABufferSinkContext structure, which defines the incoming buffers’ formats, to be passed as the opaque parameter to `avfilter_init_filter` for initialization.

## 16.2 anullsink

Null audio sink, do absolutely nothing with the input audio. It is mainly useful as a template and to be employed in analysis / debugging tools.

# 17. Video Filters

When you configure your FFmpeg build, you can disable any of the existing filters using `--disable-filters`. The configure output will show the video filters included in your build.

Below is a description of the currently available video filters.

## 17.1 ass

Draw ASS (Advanced Substation Alpha) subtitles on top of input video using the libass library.

To enable compilation of this filter you need to configure FFmpeg with `--enable-libass`.

This filter accepts the syntax: ass_filename[:options], where ass_filename is the filename of the ASS file to read, and options is an optional sequence of key=value pairs, separated by ":".

A description of the accepted options follows.

‘`original_size`’

  Specifies the size of the original video, the video for which the ASS file was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is necessary to correctly scale the fonts if the aspect ratio has been changed.

For example, to render the file ‘`sub.ass`’ on top of the input video, use the command:

    ass=sub.ass

## 17.2 bbox

Compute the bounding box for the non-black pixels in the input frame luminance plane.

This filter computes the bounding box containing all the pixels with a luminance value greater than the minimum allowed value. The parameters describing the bounding box are printed on the filter log.

## 17.3 blackdetect

Detect video intervals that are (almost) completely black. Can be useful to detect chapter transitions, commercials, or invalid recordings. Output lines contains the time for the start, end and duration of the detected black interval expressed in seconds.

In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.

This filter accepts a list of options in the form of key=value pairs separated by ":". A description of the accepted options follows.

‘`black_min_duration, d`’

  Set the minimum detected black duration expressed in seconds. It must be a non-negative floating point number.

  Default value is 2.0.

‘`picture_black_ratio_th, pic_th`’

  Set the threshold for considering a picture "black". Express the minimum value for the ratio:

      nb_black_pixels / nb_pixels

  for which a picture is considered black. Default value is 0.98.

‘`pixel_black_th, pix_th`’

  Set the threshold for considering a pixel "black".

  The threshold expresses the maximum pixel luminance value for which a pixel is considered "black". The provided value is scaled according to the following equation:

      absolute_threshold = luminance_minimum_value + pixel_black_th * luminance_range_size

  luminance_range_size and luminance_minimum_value depend on the input video format, the range is [0-255] for YUV full-range formats and [16-235] for YUV non full-range formats.

  Default value is 0.10.

The following example sets the maximum pixel threshold to the minimum value, and detects only black intervals of 2 or more seconds:

    blackdetect=d=2:pix_th=0.00

## 17.4 blackframe

Detect frames that are (almost) completely black. Can be useful to detect chapter transitions or commercials. Output lines consist of the frame number of the detected frame, the percentage of blackness, the position in the file if known or -1 and the timestamp in seconds.

In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.

The filter accepts the syntax:

    blackframe[=amount:[threshold]]

amount is the percentage of the pixels that have to be below the threshold, and defaults to 98.

threshold is the threshold below which a pixel value is considered black, and defaults to 32.

## 17.5 boxblur

Apply boxblur algorithm to the input video.

This filter accepts the parameters: luma_radius:luma_power:chroma_radius:chroma_power:alpha_radius:alpha_power

Chroma and alpha parameters are optional, if not specified they default to the corresponding values set for luma_radius and luma_power.

luma_radius, chroma_radius, and alpha_radius represent the radius in pixels of the box used for blurring the corresponding input plane. They are expressions, and can contain the following constants:

‘`w, h`’

  the input width and height in pixels

‘`cw, ch`’

  the input chroma image width and height in pixels

‘`hsub, vsub`’

  horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

The radius must be a non-negative number, and must not be greater than the value of the expression `min(w,h)/2` for the luma and alpha planes, and of `min(cw,ch)/2` for the chroma planes.

luma_power, chroma_power, and alpha_power represent how many times the boxblur filter is applied to the corresponding plane.

Some examples follow:

- Apply a boxblur filter with luma, chroma, and alpha radius set to 2:

      boxblur=2:1

- Set luma radius to 2, alpha and chroma radius to 0

      boxblur=2:1:0:0:0:0

- Set luma and chroma radius to a fraction of the video dimension

      boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1

## 17.6 colormatrix

The colormatrix filter allows conversion between any of the following color space: BT.709 (bt709), BT.601 (bt601), SMPTE-240M (smpte240m) and FCC (fcc).

The syntax of the parameters is source:destination:

    colormatrix=bt601:smpte240m

## 17.7 copy

Copy the input source unchanged to the output. Mainly useful for testing purposes.

## 17.8 crop

Crop the input video to out_w:out_h:x:y:keep_aspect

The keep_aspect parameter is optional, if specified and set to a non-zero value will force the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio.

The out_w, out_h, x, y parameters are expressions containing the following constants:

‘`x, y`’

  the computed values for x and y. They are evaluated for each new frame.

‘`in_w, in_h`’

  the input width and height

‘`iw, ih`’

  same as in_w and in_h

‘`out_w, out_h`’

  the output (cropped) width and height

‘`ow, oh`’

  same as out_w and out_h

‘`a`’

  same as iw / ih

‘`sar`’

  input sample aspect ratio

‘`dar`’

  input display aspect ratio, it is the same as (iw / ih) * sar

‘`hsub, vsub`’

  horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

‘`n`’

  the number of input frame, starting from 0

‘`pos`’

  the position in the file of the input frame, NAN if unknown

‘`t`’

  timestamp expressed in seconds, NAN if the input timestamp is unknown

The out_w and out_h parameters specify the expressions for the width and height of the output (cropped) video. They are evaluated just at the configuration of the filter.

The default value of out_w is "in_w", and the default value of out_h is "in_h".

The expression for out_w may depend on the value of out_h, and the expression for out_h may depend on out_w, but they cannot depend on x and y, as x and y are evaluated after out_w and out_h.

The x and y parameters specify the expressions for the position of the top-left corner of the output (non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is approximated to the nearest valid value.

The default value of x is "(in_w-out_w)/2", and the default value for y is "(in_h-out_h)/2", which set the cropped area at the center of the input image.

The expression for x may depend on y, and the expression for y may depend on x.

Follow some examples:

    # crop the central input area with size 100x100
    crop=100:100

    # crop the central input area with size 2/3 of the input video
    "crop=2/3*in_w:2/3*in_h"

    # crop the input video central square
    crop=in_h

    # delimit the rectangle with the top-left corner placed at position
    # 100:100 and the right-bottom corner corresponding to the right-bottom
    # corner of the input image.
    crop=in_w-100:in_h-100:100:100

    # crop 10 pixels from the left and right borders, and 20 pixels from
    # the top and bottom borders
    "crop=in_w-2*10:in_h-2*20"

    # keep only the bottom right quarter of the input image
    "crop=in_w/2:in_h/2:in_w/2:in_h/2"

    # crop height for getting Greek harmony
    "crop=in_w:1/PHI*in_w"

    # trembling effect
    "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"

    # erratic camera effect depending on timestamp
    "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"

    # set x depending on the value of y
    "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"

## 17.9 cropdetect

Auto-detect crop size.

Calculate necessary cropping parameters and prints the recommended parameters through the logging system. The detected dimensions correspond to the non-black area of the input video.

It accepts the syntax:

    cropdetect[=limit[:round[:reset]]]

‘`limit`’

  Threshold, which can be optionally specified from nothing (0) to everything (255), defaults to 24.

‘`round`’

  Value which the width/height should be divisible by, defaults to 16. The offset is automatically adjusted to center the video. Use 2 to get only even dimensions (needed for 4:2:2 video). 16 is best when encoding to most video codecs.

‘`reset`’

  Counter that determines after how many frames cropdetect will reset the previously detected largest video area and start over to detect the current optimal crop area. Defaults to 0.

  This can be useful when channel logos distort the video area. 0 indicates never reset and return the largest area encountered during playback.

## 17.10 delogo

Suppress a TV station logo by a simple interpolation of the surrounding pixels. Just set a rectangle covering the logo and watch it disappear (and sometimes something even uglier appear - your mileage may vary).

The filter accepts parameters as a string of the form "x:y:w:h:band", or as a list of key=value pairs, separated by ":".

The description of the accepted parameters follows.

‘`x, y`’

  Specify the top left corner coordinates of the logo. They must be specified.

‘`w, h`’

  Specify the width and height of the logo to clear. They must be specified.

‘`band, t`’

  Specify the thickness of the fuzzy edge of the rectangle (added to w and h). The default value is 4.

‘`show`’

  When set to 1, a green rectangle is drawn on the screen to simplify finding the right x, y, w, h parameters, and band is set to 4. The default value is 0.

Some examples follow.

- Set a rectangle covering the area with top left corner coordinates 0,0 and size 100x77, setting a band of size 10:

      delogo=0:0:100:77:10

- As the previous example, but use named options:

      delogo=x=0:y=0:w=100:h=77:band=10

## 17.11 deshake

Attempt to fix small changes in horizontal and/or vertical shift. This filter helps remove camera shake from hand-holding a camera, bumping a tripod, moving on a vehicle, etc.

The filter accepts parameters as a string of the form "x:y:w:h:rx:ry:edge:blocksize:contrast:search:filename"

A description of the accepted parameters follows.

‘`x, y, w, h`’

  Specify a rectangular area where to limit the search for motion vectors. If desired the search for motion vectors can be limited to a rectangular area of the frame defined by its top left corner, width and height. These parameters have the same meaning as the drawbox filter which can be used to visualise the position of the bounding box.

  This is useful when simultaneous movement of subjects within the frame might be confused for camera motion by the motion vector search.

  If any or all of x, y, w and h are set to -1 then the full frame is used. This allows later options to be set without specifying the bounding box for the motion vector search.

  Default - search the whole frame.

‘`rx, ry`’

  Specify the maximum extent of movement in x and y directions in the range 0-64 pixels. Default 16.

‘`edge`’

  Specify how to generate pixels to fill blanks at the edge of the frame. An integer from 0 to 3 as follows:

  ‘`0`’

    Fill zeroes at blank locations

  ‘`1`’

    Original image at blank locations

  ‘`2`’

    Extruded edge value at blank locations

  ‘`3`’

    Mirrored edge at blank locations

  The default setting is mirror edge at blank locations.

‘`blocksize`’

  Specify the blocksize to use for motion search. Range 4-128 pixels, default 8.

‘`contrast`’

  Specify the contrast threshold for blocks. Only blocks with more than the specified contrast (difference between darkest and lightest pixels) will be considered. Range 1-255, default 125.

‘`search`’

  Specify the search strategy 0 = exhaustive search, 1 = less exhaustive search. Default - exhaustive search.

‘`filename`’

  If set then a detailed log of the motion search is written to the specified file.

## 17.12 drawbox

Draw a colored box on the input image.

It accepts the syntax:

    drawbox=x:y:width:height:color

‘`x, y`’

  Specify the top left corner coordinates of the box. Default to 0.

‘`width, height`’

  Specify the width and height of the box, if 0 they are interpreted as the input width and height. Default to 0.

‘`color`’

  Specify the color of the box to write, it can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence.

Follow some examples:

    # draw a black box around the edge of the input image
    drawbox

    # draw a box with color red and an opacity of 50%
    drawbox=10:20:200:60:red@0.5"

## 17.13 drawtext

Draw text string or text from specified file on top of video using the libfreetype library.

To enable compilation of this filter you need to configure FFmpeg with `--enable-libfreetype`.

The filter also recognizes strftime() sequences in the provided text and expands them accordingly. Check the documentation of strftime().

The filter accepts parameters as a list of key=value pairs, separated by ":".

The description of the accepted parameters follows.

‘`fontfile`’

  The font file to be used for drawing text. Path must be included. This parameter is mandatory.

‘`text`’

  The text string to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter is mandatory if no file is specified with the parameter textfile.

‘`textfile`’

  A text file containing text to be drawn. The text must be a sequence of UTF-8 encoded characters.

  This parameter is mandatory if no text string is specified with the parameter text.

  If both text and textfile are specified, an error is thrown.

‘`x, y`’

  The expressions which specify the offsets where text will be drawn within the video frame. They are relative to the top/left border of the output image.

  The default value of x and y is "0".

  See below for the list of accepted constants.

‘`fontsize`’

  The font size to be used for drawing text. The default value of fontsize is 16.

‘`fontcolor`’

  The color to be used for drawing fonts. Either a string (e.g. "red") or in 0xRRGGBB[AA] format (e.g. "0xff000033"), possibly followed by an alpha specifier. The default value of fontcolor is "black".

‘`boxcolor`’

  The color to be used for drawing box around text. Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of boxcolor is "white".

‘`box`’

  Used to draw a box around text using background color. Value should be either 1 (enable) or 0 (disable). The default value of box is 0.

‘`shadowx, shadowy`’

  The x and y offsets for the text shadow position with respect to the position of the text. They can be either positive or negative values. Default value for both is "0".

‘`shadowcolor`’

  The color to be used for drawing a shadow behind the drawn text. It can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA] form (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of shadowcolor is "black".

‘`ft_load_flags`’

  Flags to be used for loading the fonts.

  The flags map the corresponding flags supported by libfreetype, and are a combination of the following values:

  default
  no_scale
  no_hinting
  render
  no_bitmap
  vertical_layout
  force_autohint
  crop_bitmap
  pedantic
  ignore_global_advance_width
  no_recurse
  ignore_transform
  monochrome
  linear_design
  no_autohint
  end table

  Default value is "render".

  For more information consult the documentation for the FT_LOAD_* libfreetype flags.

‘`tabsize`’

  The size in number of spaces to use for rendering the tab. Default value is 4.

‘`fix_bounds`’

  If true, check and fix text coords to avoid clipping.

The parameters for x and y are expressions containing the following constants:

‘`W, H`’

  the input width and height

‘`tw, text_w`’

  the width of the rendered text

‘`th, text_h`’

  the height of the rendered text

‘`lh, line_h`’

  the height of each text line

‘`sar`’

  input sample aspect ratio

‘`dar`’

  input display aspect ratio, it is the same as (w / h) * sar

‘`hsub, vsub`’

  horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

‘`max_glyph_w`’

  maximum glyph width, that is the maximum width for all the glyphs contained in the rendered text

‘`max_glyph_h`’

  maximum glyph height, that is the maximum height for all the glyphs contained in the rendered text, it is equivalent to ascent - descent.

‘`max_glyph_a, ascent`’

  the maximum distance from the baseline to the highest/upper grid coordinate used to place a glyph outline point, for all the rendered glyphs. It is a positive value, due to the grid’s orientation with the Y axis upwards.

‘`max_glyph_d, descent`’

  the maximum distance from the baseline to the lowest grid coordinate used to place a glyph outline point, for all the rendered glyphs. This is a negative value, due to the grid’s orientation, with the Y axis upwards.

‘`n`’

  the number of input frame, starting from 0

‘`t`’

  timestamp expressed in seconds, NAN if the input timestamp is unknown

‘`timecode`’

  initial timecode representation in "hh:mm:ss[:;.]ff" format. It can be used with or without text parameter. rate option must be specified.

‘`r, rate`’

  frame rate (timecode only)

If libavfilter was built with `--enable-fontconfig`, then ‘`fontfile`’ can be a fontconfig pattern or omitted.

Some examples follow.

- Draw "Test Text" with font FreeSerif, using the default values for the optional parameters.

      drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"

- Draw ’Test Text’ with font FreeSerif of size 24 at position x=100 and y=50 (counting from the top-left corner of the screen), text is yellow with a red box around it. Both the text and the box have an opacity of 20%.

      drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
                x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"

  Note that the double quotes are not necessary if spaces are not used within the parameter list.

- Show the text at the center of the video frame:

      drawtext=fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"

- Show a text line sliding from right to left in the last row of the video frame. The file ‘`LONG_LINE`’ is assumed to contain a single line with no newlines.

      drawtext=fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t

- Show the content of file ‘`CREDITS`’ off the bottom of the frame and scroll up.

      drawtext=fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"

- Draw a single green letter "g", at the center of the input video. The glyph baseline is placed at half screen height.

      drawtext=fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent

- Use fontconfig to set the font. Note that the colons need to be escaped.

      drawtext='fontfile=Linux Libertine O-40\\:style=Semibold:text=FFmpeg'

For more information about libfreetype, check: http://www.freetype.org/.

For more information about fontconfig, check: http://freedesktop.org/software/fontconfig/fontconfig-user.html.

## 17.14 fade

Apply fade-in/out effect to input video.

It accepts the parameters: type:start_frame:nb_frames[:options]

type specifies if the effect type, can be either "in" for fade-in, or "out" for a fade-out effect.

start_frame specifies the number of the start frame for starting to apply the fade effect.

nb_frames specifies the number of frames for which the fade effect has to last. At the end of the fade-in effect the output video will have the same intensity as the input video, at the end of the fade-out transition the output video will be completely black.

options is an optional sequence of key=value pairs, separated by ":". The description of the accepted options follows.

‘`type, t`’

  See type.

‘`start_frame, s`’

  See start_frame.

‘`nb_frames, n`’

  See nb_frames.

‘`alpha`’

  If set to 1, fade only alpha channel, if one exists on the input. Default value is 0.

A few usage examples follow, usable too as test scenarios.

    # fade in first 30 frames of video
    fade=in:0:30

    # fade out last 45 frames of a 200-frame video
    fade=out:155:45

    # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
    fade=in:0:25, fade=out:975:25

    # make first 5 frames black, then fade in from frame 5-24
    fade=in:5:20

    # fade in alpha over first 25 frames of video
    fade=in:0:25:alpha=1

## 17.15 fieldorder

Transform the field order of the input video.

It accepts one parameter which specifies the required field order that the input interlaced video will be transformed to. The parameter can assume one of the following values:

‘`0 or bff`’

  output bottom field first

‘`1 or tff`’

  output top field first

Default value is "tff".

Transformation is achieved by shifting the picture content up or down by one line, and filling the remaining line with appropriate picture content. This method is consistent with most broadcast field order converters.

If the input video is not flagged as being interlaced, or it is already flagged as being of the required output field order then this filter does not alter the incoming video.

This filter is very useful when converting to or from PAL DV material, which is bottom field first.

For example:

    ffmpeg -i in.vob -vf "fieldorder=bff" out.dv

## 17.16 fifo

Buffer input images and send them when they are requested.

This filter is mainly useful when auto-inserted by the libavfilter framework.

The filter does not take parameters.

## 17.17 format

Convert the input video to one of the specified pixel formats. Libavfilter will try to pick one that is supported for the input to the next filter.

The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24".

Some examples follow:

    # convert the input video to the format "yuv420p"
    format=yuv420p

    # convert the input video to any of the formats in the list
    format=yuv420p:yuv444p:yuv410p

## 17.18 frei0r

Apply a frei0r effect to the input video.

To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with `--enable-frei0r`.

The filter supports the syntax:

    filter_name[{:|=}param1:param2:...:paramN]

filter_name is the name to the frei0r effect to load. If the environment variable `FREI0R_PATH` is defined, the frei0r effect is searched in each one of the directories specified by the colon separated list in `FREIOR_PATH`, otherwise in the standard frei0r paths, which are in this order: ‘`HOME/.frei0r-1/lib/`’, ‘`/usr/local/lib/frei0r-1/`’, ‘`/usr/lib/frei0r-1/`’.

param1, param2, ... , paramN specify the parameters for the frei0r effect.

A frei0r effect parameter can be a boolean (whose values are specified with "y" and "n"), a double, a color (specified by the syntax R/G/B, R, G, and B being float numbers from 0.0 to 1.0) or by an `av_parse_color()` color description), a position (specified by the syntax X/Y, X and Y being float numbers) and a string.

The number and kind of parameters depend on the loaded effect. If an effect parameter is not specified the default value is set.

Some examples follow:

    # apply the distort0r effect, set the first two double parameters
    frei0r=distort0r:0.5:0.01

    # apply the colordistance effect, takes a color as first parameter
    frei0r=colordistance:0.2/0.3/0.4
    frei0r=colordistance:violet
    frei0r=colordistance:0x112233

    # apply the perspective effect, specify the top left and top right
    # image positions
    frei0r=perspective:0.2/0.2:0.8/0.2

For more information see: http://piksel.org/frei0r

## 17.19 gradfun

Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8bit color depth. Interpolate the gradients that should go where the bands are, and dither them.

This filter is designed for playback only. Do not use it prior to lossy compression, because compression tends to lose the dither and bring back the bands.

The filter takes two optional parameters, separated by ’:’: strength:radius

strength is the maximum amount by which the filter will change any one pixel. Also the threshold for detecting nearly flat regions. Acceptable values range from .51 to 255, default value is 1.2, out-of-range values will be clipped to the valid range.

radius is the neighborhood to fit the gradient to. A larger radius makes for smoother gradients, but also prevents the filter from modifying the pixels near detailed regions. Acceptable values are 8-32, default value is 16, out-of-range values will be clipped to the valid range.

    # default parameters
    gradfun=1.2:16

    # omitting radius
    gradfun=1.2

## 17.20 hflip

Flip the input video horizontally.

For example to horizontally flip the input video with `ffmpeg`:

    ffmpeg -i in.avi -vf "hflip" out.avi

## 17.21 hqdn3d

High precision/quality 3d denoise filter. This filter aims to reduce image noise producing smooth images and making still images really still. It should enhance compressibility.

It accepts the following optional parameters: luma_spatial:chroma_spatial:luma_tmp:chroma_tmp

‘`luma_spatial`’

  a non-negative float number which specifies spatial luma strength, defaults to 4.0

‘`chroma_spatial`’

  a non-negative float number which specifies spatial chroma strength, defaults to 3.0*luma_spatial/4.0

‘`luma_tmp`’

  a float number which specifies luma temporal strength, defaults to 6.0*luma_spatial/4.0

‘`chroma_tmp`’

  a float number which specifies chroma temporal strength, defaults to luma_tmp*chroma_spatial/luma_spatial

## 17.22 idet

Interlaceing detect filter. This filter tries to detect if the input is interlaced or progressive. Top or bottom field first.

## 17.23 lut, lutrgb, lutyuv

Compute a look-up table for binding each pixel component input value to an output value, and apply it to input video.

lutyuv applies a lookup table to a YUV input video, lutrgb to an RGB input video.

These filters accept in input a ":"-separated list of options, which specify the expressions used for computing the lookup table for the corresponding pixel component values.

The lut filter requires either YUV or RGB pixel formats in input, and accepts the options:

‘`c0`’

  first pixel component

‘`c1`’

  second pixel component

‘`c2`’

  third pixel component

‘`c3`’

  fourth pixel component, corresponds to the alpha component

The exact component associated to each option depends on the format in input.

The lutrgb filter requires RGB pixel formats in input, and accepts the options:

‘`r`’

  red component

‘`g`’

  green component

‘`b`’

  blue component

‘`a`’

  alpha component

The lutyuv filter requires YUV pixel formats in input, and accepts the options:

‘`y`’

  Y/luminance component

‘`u`’

  U/Cb component

‘`v`’

  V/Cr component

‘`a`’

  alpha component

The expressions can contain the following constants and functions:

‘`w, h`’

  the input width and height

‘`val`’

  input value for the pixel component

‘`clipval`’

  the input value clipped in the minval-maxval range

‘`maxval`’

  maximum value for the pixel component

‘`minval`’

  minimum value for the pixel component

‘`negval`’

  the negated value for the pixel component value clipped in the minval-maxval range , it corresponds to the expression "maxval-clipval+minval"

‘`clip(val)`’

  the computed value in val clipped in the minval-maxval range

‘`gammaval(gamma)`’

  the computed gamma correction value of the pixel component value clipped in the minval-maxval range, corresponds to the expression "pow((clipval-minval)/(maxval-minval)\,gamma)*(maxval-minval)+minval"

All expressions default to "val".

Some examples follow:

    # negate input video
    lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
    lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"

    # the above is the same as
    lutrgb="r=negval:g=negval:b=negval"
    lutyuv="y=negval:u=negval:v=negval"

    # negate luminance
    lutyuv=y=negval

    # remove chroma components, turns the video into a graytone image
    lutyuv="u=128:v=128"

    # apply a luma burning effect
    lutyuv="y=2*val"

    # remove green and blue components
    lutrgb="g=0:b=0"

    # set a constant alpha channel value on input
    format=rgba,lutrgb=a="maxval-minval/2"

    # correct luminance gamma by a 0.5 factor
    lutyuv=y=gammaval(0.5)

## 17.24 mp

Apply an MPlayer filter to the input video.

This filter provides a wrapper around most of the filters of MPlayer/MEncoder.

This wrapper is considered experimental. Some of the wrapped filters may not work properly and we may drop support for them, as they will be implemented natively into FFmpeg. Thus you should avoid depending on them when writing portable scripts.

The filters accepts the parameters: filter_name[:=]filter_params

filter_name is the name of a supported MPlayer filter, filter_params is a string containing the parameters accepted by the named filter.

The list of the currently supported filters follows:

decimate
denoise3d
detc
dint
divtc
down3dright
dsize
eq2
eq
field
fil
fixpts
framestep
fspp
geq
harddup
hqdn3d
hue
il
ilpack
ivtc
kerndeint
mcdeint
noise
ow
palette
perspective
phase
pp7
pullup
qp
rectangle
rotate
sab
screenshot
smartblur
softpulldown
softskip
spp
telecine
tile
tinterlace
unsharp
uspp
yuvcsp
yvu9

The parameter syntax and behavior for the listed filters are the same of the corresponding MPlayer filters. For detailed instructions check the "VIDEO FILTERS" section in the MPlayer manual.

Some examples follow:

    # adjust gamma, brightness, contrast
    mp=eq2=1.0:2:0.5

    # tweak hue and saturation
    mp=hue=100:-10

See also mplayer(1), http://www.mplayerhq.hu/.

## 17.25 negate

Negate input video.

This filter accepts an integer in input, if non-zero it negates the alpha component (if available). The default value in input is 0.

## 17.26 noformat

Force libavfilter not to use any of the specified pixel formats for the input to the next filter.

The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24".

Some examples follow:

    # force libavfilter to use a format different from "yuv420p" for the
    # input to the vflip filter
    noformat=yuv420p,vflip

    # convert the input video to any of the formats not contained in the list
    noformat=yuv420p:yuv444p:yuv410p

## 17.27 null

Pass the video source unchanged to the output.

## 17.28 ocv

Apply video transform using libopencv.

To enable this filter install libopencv library and headers and configure FFmpeg with `--enable-libopencv`.

The filter takes the parameters: filter_name{:=}filter_params.

filter_name is the name of the libopencv filter to apply.

filter_params specifies the parameters to pass to the libopencv filter. If not specified the default values are assumed.

Refer to the official libopencv documentation for more precise information: http://opencv.willowgarage.com/documentation/c/image_filtering.html

Follows the list of supported libopencv filters.

### 17.28.1 dilate

Dilate an image by using a specific structuring element. This filter corresponds to the libopencv function `cvDilate`.

It accepts the parameters: struct_el:nb_iterations.

struct_el represents a structuring element, and has the syntax: colsxrows+anchor_xxanchor_y/shape

cols and rows represent the number of columns and rows of the structuring element, anchor_x and anchor_y the anchor point, and shape the shape for the structuring element, and can be one of the values "rect", "cross", "ellipse", "custom".

If the value for shape is "custom", it must be followed by a string of the form "=filename". The file with name filename is assumed to represent a binary image, with each printable character corresponding to a bright pixel. When a custom shape is used, cols and rows are ignored, the number or columns and rows of the read file are assumed instead.

The default value for struct_el is "3x3+0x0/rect".

nb_iterations specifies the number of times the transform is applied to the image, and defaults to 1.

Follow some example:

    # use the default values
    ocv=dilate

    # dilate using a structuring element with a 5x5 cross, iterate two times
    ocv=dilate=5x5+2x2/cross:2

    # read the shape from the file diamond.shape, iterate two times
    # the file diamond.shape may contain a pattern of characters like this:
    #   *
    #  ***
    # *****
    #  ***
    #   *
    # the specified cols and rows are ignored (but not the anchor point coordinates)
    ocv=0x0+2x2/custom=diamond.shape:2

### 17.28.2 erode

Erode an image by using a specific structuring element. This filter corresponds to the libopencv function `cvErode`.

The filter accepts the parameters: struct_el:nb_iterations, with the same syntax and semantics as the dilate filter.

### 17.28.3 smooth

Smooth the input video.

The filter takes the following parameters: type:param1:param2:param3:param4.

type is the type of smooth filter to apply, and can be one of the following values: "blur", "blur_no_scale", "median", "gaussian", "bilateral". The default value is "gaussian".

param1, param2, param3, and param4 are parameters whose meanings depend on smooth type. param1 and param2 accept integer positive values or 0, param3 and param4 accept float values.

The default value for param1 is 3, the default value for the other parameters is 0.

These parameters correspond to the parameters assigned to the libopencv function `cvSmooth`.

## 17.29 overlay

Overlay one video on top of another.

It takes two inputs and one output, the first input is the "main" video on which the second input is overlayed.

It accepts the parameters: x:y[:options].

x is the x coordinate of the overlayed video on the main video, y is the y coordinate. x and y are expressions containing the following parameters:

‘`main_w, main_h`’

  main input width and height

‘`W, H`’

  same as main_w and main_h

‘`overlay_w, overlay_h`’

  overlay input width and height

‘`w, h`’

  same as overlay_w and overlay_h

options is an optional list of key=value pairs, separated by ":".

The description of the accepted options follows.

‘`rgb`’

  If set to 1, force the filter to accept inputs in the RGB color space. Default value is 0.

Be aware that frames are taken from each input video in timestamp order, hence, if their initial timestamps differ, it is a a good idea to pass the two inputs through a setpts=PTS-STARTPTS filter to have them begin in the same zero timestamp, as it does the example for the movie filter.

Follow some examples:

    # draw the overlay at 10 pixels from the bottom right
    # corner of the main video.
    overlay=main_w-overlay_w-10:main_h-overlay_h-10

    # insert a transparent PNG logo in the bottom left corner of the input
    ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output

    # insert 2 different transparent PNG logos (second logo on bottom
    # right corner):
    ffmpeg -i input -i logo1 -i logo2 -filter_complex
    'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output

    # add a transparent color layer on top of the main video,
    # WxH specifies the size of the main input to the overlay filter
    color=red.3:WxH [over]; [in][over] overlay [out]

You can chain together more overlays but the efficiency of such approach is yet to be tested.

## 17.30 pad

Add paddings to the input image, and places the original input at the given coordinates x, y.

It accepts the following parameters: width:height:x:y:color.

The parameters width, height, x, and y are expressions containing the following constants:

‘`in_w, in_h`’

  the input video width and height

‘`iw, ih`’

  same as in_w and in_h

‘`out_w, out_h`’

  the output width and height, that is the size of the padded area as specified by the width and height expressions

‘`ow, oh`’

  same as out_w and out_h

‘`x, y`’

  x and y offsets as specified by the x and y expressions, or NAN if not yet specified

‘`a`’

  same as iw / ih

‘`sar`’

  input sample aspect ratio

‘`dar`’

  input display aspect ratio, it is the same as (iw / ih) * sar

‘`hsub, vsub`’

  horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

Follows the description of the accepted parameters.

‘`width, height`’

  Specify the size of the output image with the paddings added. If the value for width or height is 0, the corresponding input size is used for the output.

  The width expression can reference the value set by the height expression, and vice versa.

  The default value of width and height is 0.

‘`x, y`’

  Specify the offsets where to place the input image in the padded area with respect to the top/left border of the output image.

  The x expression can reference the value set by the y expression, and vice versa.

  The default value of x and y is 0.

‘`color`’

  Specify the color of the padded area, it can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence.

  The default value of color is "black".

Some examples follow:

    # Add paddings with color "violet" to the input video. Output video
    # size is 640x480, the top-left corner of the input video is placed at
    # column 0, row 40.
    pad=640:480:0:40:violet

    # pad the input to get an output with dimensions increased bt 3/2,
    # and put the input video at the center of the padded area
    pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"

    # pad the input to get a squared output with size equal to the maximum
    # value between the input width and height, and put the input video at
    # the center of the padded area
    pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"

    # pad the input to get a final w/h ratio of 16:9
    pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"

    # for anamorphic video, in order to set the output display aspect ratio,
    # it is necessary to use sar in the expression, according to the relation:
    # (ih * X / ih) * sar = output_dar
    # X = output_dar / sar
    pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"

    # double output size and put the input video in the bottom-right
    # corner of the output padded area
    pad="2*iw:2*ih:ow-iw:oh-ih"

## 17.31 pixdesctest

Pixel format descriptor test filter, mainly useful for internal testing. The output video should be equal to the input video.

For example:

    format=monow, pixdesctest

can be used to test the monowhite pixel format descriptor definition.

## 17.32 removelogo

Suppress a TV station logo, using an image file to determine which pixels comprise the logo. It works by filling in the pixels that comprise the logo with neighboring pixels.

This filter requires one argument which specifies the filter bitmap file, which can be any image format supported by libavformat. The width and height of the image file must match those of the video stream being processed.

Pixels in the provided bitmap image with a value of zero are not considered part of the logo, non-zero pixels are considered part of the logo. If you use white (255) for the logo and black (0) for the rest, you will be safe. For making the filter bitmap, it is recommended to take a screen capture of a black frame with the logo visible, and then using a threshold filter followed by the erode filter once or twice.

If needed, little splotches can be fixed manually. Remember that if logo pixels are not covered, the filter quality will be much reduced. Marking too many pixels as part of the logo does not hurt as much, but it will increase the amount of blurring needed to cover over the image and will destroy more information than necessary, and extra pixels will slow things down on a large logo.

## 17.33 scale

Scale the input video to width:height[:interl={1|-1}] and/or convert the image format.

The scale filter forces the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio.

The parameters width and height are expressions containing the following constants:

‘`in_w, in_h`’

  the input width and height

‘`iw, ih`’

  same as in_w and in_h

‘`out_w, out_h`’

  the output (cropped) width and height

‘`ow, oh`’

  same as out_w and out_h

‘`a`’

  same as iw / ih

‘`sar`’

  input sample aspect ratio

‘`dar`’

  input display aspect ratio, it is the same as (iw / ih) * sar

‘`hsub, vsub`’

  horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

If the input image format is different from the format requested by the next filter, the scale filter will convert the input to the requested format.

If the value for width or height is 0, the respective input size is used for the output.

If the value for width or height is -1, the scale filter will use, for the respective output size, a value that maintains the aspect ratio of the input image.

The default value of width and height is 0.

Valid values for the optional parameter interl are:

‘`1`’

  force interlaced aware scaling

‘`-1`’

  select interlaced aware scaling depending on whether the source frames are flagged as interlaced or not

Unless interl is set to one of the above options, interlaced scaling will not be used.

Some examples follow:

    # scale the input video to a size of 200x100.
    scale=200:100

    # scale the input to 2x
    scale=2*iw:2*ih
    # the above is the same as
    scale=2*in_w:2*in_h

    # scale the input to 2x with forced interlaced scaling
    scale=2*iw:2*ih:interl=1

    # scale the input to half size
    scale=iw/2:ih/2

    # increase the width, and set the height to the same size
    scale=3/2*iw:ow

    # seek for Greek harmony
    scale=iw:1/PHI*iw
    scale=ih*PHI:ih

    # increase the height, and set the width to 3/2 of the height
    scale=3/2*oh:3/5*ih

    # increase the size, but make the size a multiple of the chroma
    scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"

    # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
    scale='min(500\, iw*3/2):-1'

## 17.34 select

Select frames to pass in output.

It accepts in input an expression, which is evaluated for each input frame. If the expression is evaluated to a non-zero value, the frame is selected and passed to the output, otherwise it is discarded.

The expression can contain the following constants:

‘`n`’

  the sequential number of the filtered frame, starting from 0

‘`selected_n`’

  the sequential number of the selected frame, starting from 0

‘`prev_selected_n`’

  the sequential number of the last selected frame, NAN if undefined

‘`TB`’

  timebase of the input timestamps

‘`pts`’

  the PTS (Presentation TimeStamp) of the filtered video frame, expressed in TB units, NAN if undefined

‘`t`’

  the PTS (Presentation TimeStamp) of the filtered video frame, expressed in seconds, NAN if undefined

‘`prev_pts`’

  the PTS of the previously filtered video frame, NAN if undefined

‘`prev_selected_pts`’

  the PTS of the last previously filtered video frame, NAN if undefined

‘`prev_selected_t`’

  the PTS of the last previously selected video frame, NAN if undefined

‘`start_pts`’

  the PTS of the first video frame in the video, NAN if undefined

‘`start_t`’

  the time of the first video frame in the video, NAN if undefined

‘`pict_type`’

  the type of the filtered frame, can assume one of the following values:

  ‘`I`’
  ‘`P`’
  ‘`B`’
  ‘`S`’
  ‘`SI`’
  ‘`SP`’
  ‘`BI`’
‘`interlace_type`’

  the frame interlace type, can assume one of the following values:

  ‘`PROGRESSIVE`’

    the frame is progressive (not interlaced)

  ‘`TOPFIRST`’

    the frame is top-field-first

  ‘`BOTTOMFIRST`’

    the frame is bottom-field-first

‘`key`’

  1 if the filtered frame is a key-frame, 0 otherwise

‘`pos`’

  the position in the file of the filtered frame, -1 if the information is not available (e.g. for synthetic video)

The default value of the select expression is "1".

Some examples follow:

    # select all frames in input
    select

    # the above is the same as:
    select=1

    # skip all frames:
    select=0

    # select only I-frames
    select='eq(pict_type\,I)'

    # select one frame every 100
    select='not(mod(n\,100))'

    # select only frames contained in the 10-20 time interval
    select='gte(t\,10)*lte(t\,20)'

    # select only I frames contained in the 10-20 time interval
    select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'

    # select frames with a minimum distance of 10 seconds
    select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'

## 17.35 setdar, setsar

The `setdar` filter sets the Display Aspect Ratio for the filter output video.

This is done by changing the specified Sample (aka Pixel) Aspect Ratio, according to the following equation:

    DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR

Keep in mind that the `setdar` filter does not modify the pixel dimensions of the video frame. Also the display aspect ratio set by this filter may be changed by later filters in the filterchain, e.g. in case of scaling or if another "setdar" or a "setsar" filter is applied.

The `setsar` filter sets the Sample (aka Pixel) Aspect Ratio for the filter output video.

Note that as a consequence of the application of this filter, the output display aspect ratio will change according to the equation above.

Keep in mind that the sample aspect ratio set by the `setsar` filter may be changed by later filters in the filterchain, e.g. if another "setsar" or a "setdar" filter is applied.

The `setdar` and `setsar` filters accept a parameter string which represents the wanted aspect ratio. The parameter can be a floating point number string, an expression, or a string of the form num:den, where num and den are the numerator and denominator of the aspect ratio. If the parameter is not specified, it is assumed the value "0:1".

For example to change the display aspect ratio to 16:9, specify:

    setdar=16:9

The example above is equivalent to:

    setdar=1.77777

To change the sample aspect ratio to 10:11, specify:

    setsar=10:11

## 17.36 setfield

Force field for the output video frame.

The `setfield` filter marks the interlace type field for the output frames. It does not change the input frame, but only sets the corresponding property, which affects how the frame is treated by following filters (e.g. `fieldorder` or `yadif`).

It accepts a string parameter, which can assume the following values:

‘`auto`’

  Keep the same field property.

‘`bff`’

  Mark the frame as bottom-field-first.

‘`tff`’

  Mark the frame as top-field-first.

‘`prog`’

  Mark the frame as progressive.

## 17.37 setpts

Change the PTS (presentation timestamp) of the input video frames.

Accept in input an expression evaluated through the eval API, which can contain the following constants:

‘`PTS`’

  the presentation timestamp in input

‘`N`’

  the count of the input frame, starting from 0.

‘`STARTPTS`’

  the PTS of the first video frame

‘`INTERLACED`’

  tell if the current frame is interlaced

‘`POS`’

  original position in the file of the frame, or undefined if undefined for the current frame

‘`PREV_INPTS`’

  previous input PTS

‘`PREV_OUTPTS`’

  previous output PTS

Some examples follow:

    # start counting PTS from zero
    setpts=PTS-STARTPTS

    # fast motion
    setpts=0.5*PTS

    # slow motion
    setpts=2.0*PTS

    # fixed rate 25 fps
    setpts=N/(25*TB)

    # fixed rate 25 fps with some jitter
    setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'

## 17.38 settb

Set the timebase to use for the output frames timestamps. It is mainly useful for testing timebase configuration.

It accepts in input an arithmetic expression representing a rational. The expression can contain the constants "AVTB" (the default timebase), and "intb" (the input timebase).

The default value for the input is "intb".

Follow some examples.

    # set the timebase to 1/25
    settb=1/25

    # set the timebase to 1/10
    settb=0.1

    #set the timebase to 1001/1000
    settb=1+0.001

    #set the timebase to 2*intb
    settb=2*intb

    #set the default timebase value
    settb=AVTB

## 17.39 showinfo

Show a line containing various information for each input video frame. The input video is not modified.

The shown line contains a sequence of key/value pairs of the form key:value.

A description of each shown parameter follows:

‘`n`’

  sequential number of the input frame, starting from 0

‘`pts`’

  Presentation TimeStamp of the input frame, expressed as a number of time base units. The time base unit depends on the filter input pad.

‘`pts_time`’

  Presentation TimeStamp of the input frame, expressed as a number of seconds

‘`pos`’

  position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic video)

‘`fmt`’

  pixel format name

‘`sar`’

  sample aspect ratio of the input frame, expressed in the form num/den

‘`s`’

  size of the input frame, expressed in the form widthxheight

‘`i`’

  interlaced mode ("P" for "progressive", "T" for top field first, "B" for bottom field first)

‘`iskey`’

  1 if the frame is a key frame, 0 otherwise

‘`type`’

  picture type of the input frame ("I" for an I-frame, "P" for a P-frame, "B" for a B-frame, "?" for unknown type). Check also the documentation of the `AVPictureType` enum and of the `av_get_picture_type_char` function defined in ‘`libavutil/avutil.h`’.

‘`checksum`’

  Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame

‘`plane_checksum`’

  Adler-32 checksum (printed in hexadecimal) of each plane of the input frame, expressed in the form "[c0 c1 c2 c3]"

## 17.40 slicify

Pass the images of input video on to next video filter as multiple slices.

    ffmpeg -i in.avi -vf "slicify=32" out.avi

The filter accepts the slice height as parameter. If the parameter is not specified it will use the default value of 16.

Adding this in the beginning of filter chains should make filtering faster due to better use of the memory cache.

## 17.41 split

Pass on the input video to two outputs. Both outputs are identical to the input video.

For example:

    [in] split [splitout1][splitout2];
    [splitout1] crop=100:100:0:0    [cropout];
    [splitout2] pad=200:200:100:100 [padout];

will create two separate outputs from the same input, one cropped and one padded.

## 17.42 super2xsai

Scale the input by 2x and smooth using the Super2xSaI (Scale and Interpolate) pixel art scaling algorithm.

Useful for enlarging pixel art images without reducing sharpness.

## 17.43 swapuv

Swap U & V plane.

## 17.44 thumbnail

Select the most representative frame in a given sequence of consecutive frames.

It accepts as argument the frames batch size to analyze (default N=100); in a set of N frames, the filter will pick one of them, and then handle the next batch of N frames until the end.

Since the filter keeps track of the whole frames sequence, a bigger N value will result in a higher memory usage, so a high value is not recommended.

The following example extract one picture each 50 frames:

    thumbnail=50

Complete example of a thumbnail creation with `ffmpeg`:

    ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png

## 17.45 tile

Tile several successive frames together.

It accepts as argument the tile size (i.e. the number of lines and columns) in the form "wxh".

For example, produce 8×8 PNG tiles of all keyframes (‘`-skip_frame nokey`’) in a movie:

    ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png

The ‘`-vsync 0`’ is necessary to prevent `ffmpeg` from duplicating each output frame to accomodate the originally detected frame rate.

## 17.46 tinterlace

Perform various types of temporal field interlacing.

Frames are counted starting from 1, so the first input frame is considered odd.

This filter accepts a single parameter specifying the mode. Available modes are:

‘`0`’

  Move odd frames into the upper field, even into the lower field, generating a double height frame at half framerate.

‘`1`’

  Only output even frames, odd frames are dropped, generating a frame with unchanged height at half framerate.

‘`2`’

  Only output odd frames, even frames are dropped, generating a frame with unchanged height at half framerate.

‘`3`’

  Expand each frame to full height, but pad alternate lines with black, generating a frame with double height at the same input framerate.

‘`4`’

  Interleave the upper field from odd frames with the lower field from even frames, generating a frame with unchanged height at half framerate.

‘`5`’

  Interleave the lower field from odd frames with the upper field from even frames, generating a frame with unchanged height at half framerate.

Default mode is 0.

## 17.47 transpose

Transpose rows with columns in the input video and optionally flip it.

It accepts a parameter representing an integer, which can assume the values:

‘`0`’

  Rotate by 90 degrees counterclockwise and vertically flip (default), that is:

      L.R     L.l
      . . ->  . .
      l.r     R.r

‘`1`’

  Rotate by 90 degrees clockwise, that is:

      L.R     l.L
      . . ->  . .
      l.r     r.R

‘`2`’

  Rotate by 90 degrees counterclockwise, that is:

      L.R     R.r
      . . ->  . .
      l.r     L.l

‘`3`’

  Rotate by 90 degrees clockwise and vertically flip, that is:

      L.R     r.R
      . . ->  . .
      l.r     l.L

## 17.48 unsharp

Sharpen or blur the input video.

It accepts the following parameters: luma_msize_x:luma_msize_y:luma_amount:chroma_msize_x:chroma_msize_y:chroma_amount

Negative values for the amount will blur the input video, while positive values will sharpen. All parameters are optional and default to the equivalent of the string ’5:5:1.0:5:5:0.0’.

‘`luma_msize_x`’

  Set the luma matrix horizontal size. It can be an integer between 3 and 13, default value is 5.

‘`luma_msize_y`’

  Set the luma matrix vertical size. It can be an integer between 3 and 13, default value is 5.

‘`luma_amount`’

  Set the luma effect strength. It can be a float number between -2.0 and 5.0, default value is 1.0.

‘`chroma_msize_x`’

  Set the chroma matrix horizontal size. It can be an integer between 3 and 13, default value is 5.

‘`chroma_msize_y`’

  Set the chroma matrix vertical size. It can be an integer between 3 and 13, default value is 5.

‘`chroma_amount`’

  Set the chroma effect strength. It can be a float number between -2.0 and 5.0, default value is 0.0.

    # Strong luma sharpen effect parameters
    unsharp=7:7:2.5

    # Strong blur of both luma and chroma parameters
    unsharp=7:7:-2:7:7:-2

    # Use the default values with ffmpeg
    ffmpeg -i in.avi -vf "unsharp" out.mp4

## 17.49 vflip

Flip the input video vertically.

    ffmpeg -i in.avi -vf "vflip" out.avi

## 17.50 yadif

Deinterlace the input video ("yadif" means "yet another deinterlacing filter").

It accepts the optional parameters: mode:parity:auto.

mode specifies the interlacing mode to adopt, accepts one of the following values:

‘`0`’

  output 1 frame for each frame

‘`1`’

  output 1 frame for each field

‘`2`’

  like 0 but skips spatial interlacing check

‘`3`’

  like 1 but skips spatial interlacing check

Default value is 0.

parity specifies the picture field parity assumed for the input interlaced video, accepts one of the following values:

‘`0`’

  assume top field first

‘`1`’

  assume bottom field first

‘`-1`’

  enable automatic detection

Default value is -1. If interlacing is unknown or decoder does not export this information, top field first will be assumed.

auto specifies if deinterlacer should trust the interlaced flag and only deinterlace frames marked as interlaced

‘`0`’

  deinterlace all frames

‘`1`’

  only deinterlace frames marked as interlaced

Default value is 0.

# 18. Video Sources

Below is a description of the currently available video sources.

## 18.1 buffer

Buffer video frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular through the interface defined in ‘`libavfilter/vsrc_buffer.h`’.

It accepts the following parameters: width:height:pix_fmt_string:timebase_num:timebase_den:sample_aspect_ratio_num:sample_aspect_ratio.den:scale_params

All the parameters but scale_params need to be explicitly defined.

Follows the list of the accepted parameters.

‘`width, height`’

  Specify the width and height of the buffered video frames.

‘`pix_fmt_string`’

  A string representing the pixel format of the buffered video frames. It may be a number corresponding to a pixel format, or a pixel format name.

‘`timebase_num, timebase_den`’

  Specify numerator and denomitor of the timebase assumed by the timestamps of the buffered frames.

‘`sample_aspect_ratio.num, sample_aspect_ratio.den`’

  Specify numerator and denominator of the sample aspect ratio assumed by the video frames.

‘`scale_params`’

  Specify the optional parameters to be used for the scale filter which is automatically inserted when an input change is detected in the input size or format.

For example:

    buffer=320:240:yuv410p:1:24:1:1

will instruct the source to accept video frames with size 320x240 and with format "yuv410p", assuming 1/24 as the timestamps timebase and square pixels (1:1 sample aspect ratio). Since the pixel format with name "yuv410p" corresponds to the number 6 (check the enum PixelFormat definition in ‘`libavutil/pixfmt.h`’), this example corresponds to:

    buffer=320:240:6:1:24:1:1

## 18.2 cellauto

Create a pattern generated by an elementary cellular automaton.

The initial state of the cellular automaton can be defined through the ‘`filename`’, and ‘`pattern`’ options. If such options are not specified an initial state is created randomly.

At each new frame a new row in the video is filled with the result of the cellular automaton next generation. The behavior when the whole frame is filled is defined by the ‘`scroll`’ option.

This source accepts a list of options in the form of key=value pairs separated by ":". A description of the accepted options follows.

‘`filename, f`’

  Read the initial cellular automaton state, i.e. the starting row, from the specified file. In the file, each non-whitespace character is considered an alive cell, a newline will terminate the row, and further characters in the file will be ignored.

‘`pattern, p`’

  Read the initial cellular automaton state, i.e. the starting row, from the specified string.

  Each non-whitespace character in the string is considered an alive cell, a newline will terminate the row, and further characters in the string will be ignored.

‘`rate, r`’

  Set the video rate, that is the number of frames generated per second. Default is 25.

‘`random_fill_ratio, ratio`’

  Set the random fill ratio for the initial cellular automaton row. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI.

  This option is ignored when a file or a pattern is specified.

‘`random_seed, seed`’

  Set the seed for filling randomly the initial row, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

‘`rule`’

  Set the cellular automaton rule, it is a number ranging from 0 to 255. Default value is 110.

‘`size, s`’

  Set the size of the output video.

  If ‘`filename`’ or ‘`pattern`’ is specified, the size is set by default to the width of the specified initial state row, and the height is set to width * PHI.

  If ‘`size`’ is set, it must contain the width of the specified pattern string, and the specified pattern will be centered in the larger row.

  If a filename or a pattern string is not specified, the size value defaults to "320x518" (used for a randomly generated initial state).

‘`scroll`’

  If set to 1, scroll the output upward when all the rows in the output have been already filled. If set to 0, the new generated row will be written over the top row just after the bottom row is filled. Defaults to 1.

‘`start_full, full`’

  If set to 1, completely fill the output with generated rows before outputting the first frame. This is the default behavior, for disabling set the value to 0.

‘`stitch`’

  If set to 1, stitch the left and right row edges together. This is the default behavior, for disabling set the value to 0.

### 18.2.1 Examples

- Read the initial state from ‘`pattern`’, and specify an output of size 200x400.

      cellauto=f=pattern:s=200x400

- Generate a random initial row with a width of 200 cells, with a fill ratio of 2/3:

      cellauto=ratio=2/3:s=200x200

- Create a pattern generated by rule 18 starting by a single alive cell centered on an initial row with width 100:

      cellauto=p=@:s=100x400:full=0:rule=18

- Specify a more elaborated initial pattern:

      cellauto=p='@@ @ @@':s=100x400:full=0:rule=18

## 18.3 color

Provide an uniformly colored input.

It accepts the following parameters: color:frame_size:frame_rate

Follows the description of the accepted parameters.

‘`color`’

  Specify the color of the source. It can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The default value is "black".

‘`frame_size`’

  Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a size abbreviation. The default value is "320x240".

‘`frame_rate`’

  Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25".

For example the following graph description will generate a red source with an opacity of 0.2, with size "qcif" and a frame rate of 10 frames per second, which will be overlayed over the source connected to the pad with identifier "in".

    "color=red@0.2:qcif:10 [color]; [in][color] overlay [out]"

## 18.4 movie

Read a video stream from a movie container.

It accepts the syntax: movie_name[:options] where movie_name is the name of the resource to read (not necessarily a file but also a device or a stream accessed through some protocol), and options is an optional sequence of key=value pairs, separated by ":".

The description of the accepted options follows.

‘`format_name, f`’

  Specifies the format assumed for the movie to read, and can be either the name of a container or an input device. If not specified the format is guessed from movie_name or by probing.

‘`seek_point, sp`’

  Specifies the seek point in seconds, the frames will be output starting from this seek point, the parameter is evaluated with `av_strtod` so the numerical value may be suffixed by an IS postfix. Default value is "0".

‘`stream_index, si`’

  Specifies the index of the video stream to read. If the value is -1, the best suited video stream will be automatically selected. Default value is "-1".

‘`loop`’

  Specifies how many times to read the video stream in sequence. If the value is less than 1, the stream will be read again and again. Default value is "1".

  Note that when the movie is looped the source timestamps are not changed, so it will generate non monotonically increasing timestamps.

This filter allows to overlay a second video on top of main input of a filtergraph as shown in this graph:

    input -----------> deltapts0 --> overlay --> output
                                        ^
                                        |
    movie --> scale--> deltapts1 -------+

Some examples follow:

    # skip 3.2 seconds from the start of the avi file in.avi, and overlay it
    # on top of the input labelled as "in".
    movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
    [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]

    # read from a video4linux2 device, and overlay it on top of the input
    # labelled as "in"
    movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
    [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]

## 18.5 mptestsrc

Generate various test patterns, as generated by the MPlayer test filter.

The size of the generated video is fixed, and is 256x256. This source is useful in particular for testing encoding features.

This source accepts an optional sequence of key=value pairs, separated by ":". The description of the accepted options follows.

‘`rate, r`’

  Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25".

‘`duration, d`’

  Set the video duration of the sourced video. The accepted syntax is:

      [-]HH[:MM[:SS[.m...]]]
      [-]S+[.m...]

  See also the function `av_parse_time()`.

  If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

‘`test, t`’

  Set the number or the name of the test to perform. Supported tests are:

  ‘`dc_luma`’
  ‘`dc_chroma`’
  ‘`freq_luma`’
  ‘`freq_chroma`’
  ‘`amp_luma`’
  ‘`amp_chroma`’
  ‘`cbp`’
  ‘`mv`’
  ‘`ring1`’
  ‘`ring2`’
  ‘`all`’

  Default value is "all", which will cycle through the list of all tests.

For example the following:

    testsrc=t=dc_luma

will generate a "dc_luma" test pattern.

## 18.6 frei0r_src

Provide a frei0r source.

To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with `--enable-frei0r`.

The source supports the syntax:

    size:rate:src_name[{=|:}param1:param2:...:paramN]

size is the size of the video to generate, may be a string of the form widthxheight or a frame size abbreviation. rate is the rate of the video to generate, may be a string of the form num/den or a frame rate abbreviation. src_name is the name to the frei0r source to load. For more information regarding frei0r and how to set the parameters read the section frei0r in the description of the video filters.

Some examples follow:

    # generate a frei0r partik0l source with size 200x200 and frame rate 10
    # which is overlayed on the overlay filter main input
    frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay

## 18.7 life

Generate a life pattern.

This source is based on a generalization of John Conway’s life game.

The sourced input represents a life grid, each pixel represents a cell which can be in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent.

At each interaction the grid evolves according to the adopted rule, which specifies the number of neighbor alive cells which will make a cell stay alive or born. The ‘`rule`’ option allows to specify the rule to adopt.

This source accepts a list of options in the form of key=value pairs separated by ":". A description of the accepted options follows.

‘`filename, f`’

  Set the file from which to read the initial grid state. In the file, each non-whitespace character is considered an alive cell, and newline is used to delimit the end of each row.

  If this option is not specified, the initial grid is generated randomly.

‘`rate, r`’

  Set the video rate, that is the number of frames generated per second. Default is 25.

‘`random_fill_ratio, ratio`’

  Set the random fill ratio for the initial random grid. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI. It is ignored when a file is specified.

‘`random_seed, seed`’

  Set the seed for filling the initial random grid, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

‘`rule`’

  Set the life rule.

  A rule can be specified with a code of the kind "SNS/BNB", where NS and NB are sequences of numbers in the range 0-8, NS specifies the number of alive neighbor cells which make a live cell stay alive, and NB the number of alive neighbor cells which make a dead cell to become alive (i.e. to "born"). "s" and "b" can be used in place of "S" and "B", respectively.

  Alternatively a rule can be specified by an 18-bits integer. The 9 high order bits are used to encode the next cell state if it is alive for each number of neighbor alive cells, the low order bits specify the rule for "borning" new cells. Higher order bits encode for an higher number of neighbor cells. For example the number 6153 = `(12<<9)+9` specifies a stay alive rule of 12 and a born rule of 9, which corresponds to "S23/B03".

  Default value is "S23/B3", which is the original Conway’s game of life rule, and will keep a cell alive if it has 2 or 3 neighbor alive cells, and will born a new cell if there are three alive cells around a dead cell.

‘`size, s`’

  Set the size of the output video.

  If ‘`filename`’ is specified, the size is set by default to the same size of the input file. If ‘`size`’ is set, it must contain the size specified in the input file, and the initial grid defined in that file is centered in the larger resulting area.

  If a filename is not specified, the size value defaults to "320x240" (used for a randomly generated initial grid).

‘`stitch`’

  If set to 1, stitch the left and right grid edges together, and the top and bottom edges also. Defaults to 1.

‘`mold`’

  Set cell mold speed. If set, a dead cell will go from ‘`death_color`’ to ‘`mold_color`’ with a step of ‘`mold`’. ‘`mold`’ can have a value from 0 to 255.

‘`life_color`’

  Set the color of living (or new born) cells.

‘`death_color`’

  Set the color of dead cells. If ‘`mold`’ is set, this is the first color used to represent a dead cell.

‘`mold_color`’

  Set mold color, for definitely dead and moldy cells.

### 18.7.1 Examples

- Read a grid from ‘`pattern`’, and center it on a grid of size 300x300 pixels:

      life=f=pattern:s=300x300

- Generate a random grid of size 200x200, with a fill ratio of 2/3:

      life=ratio=2/3:s=200x200

- Specify a custom rule for evolving a randomly generated grid:

      life=rule=S14/B34

- Full example with slow death effect (mold) using `ffplay`:

      ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16

## 18.8 nullsrc, rgbtestsrc, testsrc

The `nullsrc` source returns unprocessed video frames. It is mainly useful to be employed in analysis / debugging tools, or as the source for filters which ignore the input data.

The `rgbtestsrc` source generates an RGB test pattern useful for detecting RGB vs BGR issues. You should see a red, green and blue stripe from top to bottom.

The `testsrc` source generates a test video pattern, showing a color pattern, a scrolling gradient and a timestamp. This is mainly intended for testing purposes.

These sources accept an optional sequence of key=value pairs, separated by ":". The description of the accepted options follows.

‘`size, s`’

  Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a size abbreviation. The default value is "320x240".

‘`rate, r`’

  Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25".

‘`sar`’

  Set the sample aspect ratio of the sourced video.

‘`duration, d`’

  Set the video duration of the sourced video. The accepted syntax is:

      [-]HH[:MM[:SS[.m...]]]
      [-]S+[.m...]

  See also the function `av_parse_time()`.

  If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

‘`decimals, n`’

  Set the number of decimals to show in the timestamp, only used in the `testsrc` source.

  The displayed timestamp value will correspond to the original timestamp value multiplied by the power of 10 of the specified value. Default value is 0.

For example the following:

    testsrc=duration=5.3:size=qcif:rate=10

will generate a video with a duration of 5.3 seconds, with size 176x144 and a frame rate of 10 frames per second.

If the input content is to be ignored, `nullsrc` can be used. The following command generates noise in the luminance plane by employing the `mp=geq` filter:

    nullsrc=s=256x256, mp=geq=random(1)*255:128:128

# 19. Video Sinks

Below is a description of the currently available video sinks.

## 19.1 buffersink

Buffer video frames, and make them available to the end of the filter graph.

This sink is mainly intended for a programmatic use, in particular through the interface defined in ‘`libavfilter/buffersink.h`’.

It does not require a string parameter in input, but you need to specify a pointer to a list of supported pixel formats terminated by -1 in the opaque parameter provided to `avfilter_init_filter` when initializing this sink.

## 19.2 nullsink

Null video sink, do absolutely nothing with the input video. It is mainly useful as a template and to be employed in analysis / debugging tools.