# Limiter

`Limiter` (clip, int “min_luma”, int “max_luma”, int “min_chroma”, int “max_chroma”, string “show”)

This filter is present in v2.5. The standard known as CCIR-601 defines the range of pixel values considered legal for presenting on a TV. These ranges are 16-235 for the luma component and 16-240 for the chroma component.

Pixels outside this range are known to cause problems with some TV sets, and thus it is best to remove them before encoding if that is your intended display device. By default this filter clips (or “clamps”) pixels under 16 to 16 and over 235 (or 240) to 235 (or 240).

Prior to v2.53 the (incorrect) default value was 236. Use Limiter(16, 235, 16, 240) for CCIR-601 compliant digital video.

In v2.56, an option show is added. If set, it colors the pixels outside the specified [min_luma,max_luma] or [min_chroma,max_chroma] range.

show can be “luma” (shows out of bounds luma in red/green), “luma_grey” (shows out of bounds luma and makes the remaining pixels greyscale), “chroma” (shows out of bounds chroma in yellow), “chroma_grey” (shows out of bounds chroma and makes the remaining pixels greyscale). The coloring is done as follows:

YUY2 (chroma shared between two horizontal pixels p1 and p2: Y1UY2V): j,k=1,2
YV24 (no chroma shared): j,k=1
YV12 (chroma shared between 2x2 pixels Y11UY12V; Y21UY22V): j,k=11,12,21,22

| luma | luma_grey
--- | --- | ---
Yj < min_luma | red (pj) | red (pj)
Yj > max_luma | green (pj) | green (pj)
Yj < min_luma and Yk > max_luma | yellow (all) | puke (pj), olive (pk)

| chroma | chroma_grey
--- | --- | ---
U < min_chroma | yellow | yellow
U > max_chroma | yellow | blue
V < min_chroma | yellow | cyan
V > max_chroma | yellow | red
U < min_chroma and V < min_chroma | yellow | green
U > max_chroma and V < min_chroma | yellow | teal
U < min_chroma and V > max_chroma | yellow | orange
U > max_chroma and V > max_chroma | yellow | magenta

Changelog |
--- | ---
v2.60 | Added show for YV24.
v2.56 | added show to show out of bounds luma/chroma

$Date: 2012/04/09 08:19:32 $