Encoder libvpx [libvpx VP8]:
    Threading capabilities: no
    Supported pixel formats: yuv420p
libvpx encoder AVOptions:
-cpu-used          <int>        E..V.. Quality/Speed ratio modifier (from INT_MIN to INT_MAX)
-auto-alt-ref      <int>        E..V.. Enable use of alternate reference frames (2-pass only) (from -1 to 1)
-lag-in-frames     <int>        E..V.. Number of frames to look ahead for alternate reference frame selection (from -1 to INT_MAX)
-arnr-maxframes    <int>        E..V.. altref noise reduction max frame count (from -1 to INT_MAX)
-arnr-strength     <int>        E..V.. altref noise reduction filter strength (from -1 to INT_MAX)
-arnr-type         <int>        E..V.. altref noise reduction filter type (from -1 to INT_MAX)
   backward                     E..V..
   forward                      E..V..
   centered                     E..V..
-deadline          <int>        E..V.. Time to spend encoding, in microseconds. (from INT_MIN to INT_MAX)
   best                         E..V..
   good                         E..V..
   realtime                     E..V..
-error-resilient   <flags>      E..V.. Error resilience configuration
   default                      E..V.. Improve resiliency against losses of whole frames
   partitions                   E..V.. The frame partitions are independently decodable by the bool decoder, meaning that partitions can be decoded even though earlier partitions have been lost. Note that intra predicition is still done over the partition boundary.
-max-intra-rate    <int>        E..V.. Maximum I-frame bitrate (pct) 0=unlimited (from -1 to INT_MAX)
-speed             <int>        E..V..  (from -16 to 16)
-quality           <int>        E..V..  (from INT_MIN to INT_MAX)
   best                         E..V..
   good                         E..V..
   realtime                     E..V..
-vp8flags          <flags>      E..V.. 
   error_resilient              E..V.. enable error resilience
   altref                       E..V.. enable use of alternate reference frames (VP8/2-pass only)
-arnr_max_frames   <int>        E..V.. altref noise reduction max frame count (from 0 to 15)
-arnr_strength     <int>        E..V.. altref noise reduction filter strength (from 0 to 6)
-arnr_type         <int>        E..V.. altref noise reduction filter type (from 1 to 3)
-rc_lookahead      <int>        E..V.. Number of frames to look ahead for alternate reference frame selection (from 0 to 25)
-crf               <int>        E..V.. Select the quality for constant quality mode (from 0 to 63)

