Scale2ref

Video Multiple outputs Transform

Scale the input video size and/or convert the image format to the given reference.

FFmpeg filter: scale2ref — the official reference.

Add it to a graph. The explicit form works for every filter — bind it to its inputs and read the result from outputs():

$outputs = $video->addFilter(new Scale2ref(…), [$other])->outputs(); // one stream per output pad

Shorthand. Not available — apply() returns a single stream, and Scale2ref has multiple outputs. Use addFilter() + outputs() above.

When to use it

TODO — when this filter shines: what it’s the right tool for, what to reach for instead when it isn’t, and how it composes with neighbouring filters.

How to use it

TODO — prose: how the filter actually works and what its key parameters mean (the explanation FFmpeg’s terse option help omits).

Examples

TODO — runnable PHP, with the equivalent ffmpeg CLI alongside.

Gotchas

TODO

See also

TODO

Parameters

Parameter	Type	Default	Range / values	Description
width	int|float|string	—	expression	Output video width
height	int|float|string	—	expression	Output video height
flags	string	—	—	Flags to pass to libswscale
interl	bool	false	—	set interlacing
size	string	—	—	set video size
in_color_matrix	Scale2refColor	auto	auto, smpte170m, bt709, fcc, smpte240m, bt2020	set input YCbCr type
out_color_matrix	Scale2refColor	2	auto, smpte170m, bt709, fcc, smpte240m, bt2020	set output YCbCr type
in_range	Scale2refRange	unknown	unknown, full, limited	set input color range
out_range	Scale2refRange	unknown	unknown, full, limited	set output color range
in_chroma_loc	Scale2refChromaLoc	unknown	unknown, left, center, topleft, top, bottomleft, bottom	set input chroma sample location
out_chroma_loc	Scale2refChromaLoc	unknown	unknown, left, center, topleft, top, bottomleft, bottom	set output chroma sample location
in_v_chr_pos	int	-513	-513–512	input vertical chroma position in luma grid/256
in_h_chr_pos	int	-513	-513–512	input horizontal chroma position in luma grid/256
out_v_chr_pos	int	-513	-513–512	output vertical chroma position in luma grid/256
out_h_chr_pos	int	-513	-513–512	output horizontal chroma position in luma grid/256
force_original_aspect_ratio	Scale2refForceOar	disable	disable, decrease, increase	decrease or increase w/h if necessary to keep the original AR
force_divisible_by	int	1	1–256	enforce that the output resolution is divisible by a defined integer when force_original_aspect_ratio is used
param0	float	—	—	Scaler param 0
param1	float	—	—	Scaler param 1
eval	Scale2refEval	init	init, frame	specify when to evaluate expressions

FFmpeg also names these options (use the parameter shown above): w → width, h → height, s → size.

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Maps to FFmpeg’s scale2ref filter. Verified against ffmpeg n7.1.1.