[FFmpeg-devel] [PATCH] avfilter/vf_scale: reset color matrix in case of identity & non-RGB

[Jan Ekström]

On Sun, Aug 22, 2021 at 11:55 PM Jan Ekström <jeebjp at gmail.com> wrote:
>
> Fixes passing through mismatching metadata from the input side
> when RGB input (from f.ex. H.264 or HEVC) gets converted to YCbCr.
>
> Fixes #9132
> ---
>  libavfilter/vf_scale.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/libavfilter/vf_scale.c b/libavfilter/vf_scale.c
> index ce39217515..7ca833bbb1 100644
> --- a/libavfilter/vf_scale.c
> +++ b/libavfilter/vf_scale.c
> @@ -738,6 +738,15 @@ scale:
>      out->width  = outlink->w;
>      out->height = outlink->h;
>
> +    // Sanity check: If we've got the RGB/XYZ (identity) matrix configured, and
> +    //               the output is no longer RGB, unset the matrix.
> +    //               In theory this should be in swscale itself as the AVFrame
> +    //               based API gets in, so that not every swscale API user has
> +    //               to go through duplicating such sanity checks.
> +    if (out->colorspace == AVCOL_SPC_RGB &&
> +        !(av_pix_fmt_desc_get(out->format)->flags & AV_PIX_FMT_FLAG_RGB))
> +        out->colorspace = AVCOL_SPC_UNSPECIFIED;
> +
>      if (scale->output_is_pal)
>          avpriv_set_systematic_pal2((uint32_t*)out->data[1], outlink->format == AV_PIX_FMT_PAL8 ? AV_PIX_FMT_BGR8 : outlink->format);
>
> --
> 2.31.1
>

Unless there are objections, I will pull this in soon. I will also
attempt to see if I can add a programmatic FATE test for all of the
allowed configurations of vf_scale, to see if there are any other
clear-cut cases where not all metadata from the input AVFrame can be
passed on as-is and has to be reset.

Jan