[FFmpeg-devel] [PATCH] avfilter/vf_scale: set the RGB matrix coefficients in case of RGB

[Jan Ekström]

On Sun, Aug 29, 2021 at 10:05 PM Jan Ekström <jeebjp at gmail.com> wrote:
>
> On Sun, Aug 29, 2021 at 9:21 PM Paul B Mahol <onemda at gmail.com> wrote:
> >
> > probably fine if fate passes
>
> Yea, FATE passes :) . I think this stuff not being noticed until now
> is due to nothing checking the metadata values returned by vf_scale
> (since pix_fmt and actual logic is not changed at all with these
> output AVFrame metadata changes):
> - The first fix I did was for RGB->YCbCr still being flagged as RGB
> (and thus encoders like the libx264 wrapper would gladly comply,
> leading to bugs like issue #9132 )
> - This one fixes the opposite conversion where your YCbCr input has
> matrix coefficients configured, and the RGB output still has that
> value as-is from the av_frame_copy_props call (and once again, encoder
> complies).

If there are no further comments, I will soon apply this to fix both
sides of the YCbCr<->RGB conversion output in case the input format
happens to have the matrix coefficients configured (and thus copied
over by av_frame_copy_props). These can then be back-ported to 4.4
since it was the first release to plug input/filtered AVFrames'
metadata into output, which brought the issue of input metadata being
passed through as-is up.

The only question in my mind was whether to set it to
AVCOL_SPC_UNSPECIFIED or AVCOL_SPC_RGB . I chose the latter one since
the value literally matches what we are checking there: If output
pix_fmt is RGB, set output value to RGB.

Jan