Hi, On Mon, Feb 23, 2026 at 11:22 AM Guangyu Sun via ffmpeg-devel <[email protected]> wrote: > > When encoding VP9 with a YUV pixel format (e.g. yuv420p) and > AVCOL_SPC_RGB colorspace metadata, libvpxenc unconditionally set > VPX_CS_SRGB. This produced a spec-violating bitstream: Profile 0 > (4:2:0) with sRGB colorspace, which is only valid for Profile 1/3 > (4:4:4). The resulting file is undecodable. > > RGB pixel formats (GBRP, GBRP10, GBRP12) already correctly set > ctx->vpx_cs to VPX_CS_SRGB in set_pix_fmt() and bypass the > colorspace switch in set_colorspace(). So reaching the AVCOL_SPC_RGB > case means the pixel format is YUV with incorrect RGB metadata. > Log a warning and fall back to VPX_CS_BT_709. > > To reproduce: > > # generate a bad source > ffmpeg -f lavfi -i testsrc=s=64x64:d=1:r=1 -pix_fmt yuv420p -colorspace rgb > bad.mp4 > # transcode with default parameters > ffmpeg -i bad.mp4 bad.webm > # check decoding > ffmpeg -i bad.webm -f null - > # -> 0 frames decoded, error > > Signed-off-by: Guangyu Sun <[email protected]> > --- > libavcodec/libvpxenc.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/libavcodec/libvpxenc.c b/libavcodec/libvpxenc.c > index 88c058c403..be731a014f 100644 > --- a/libavcodec/libvpxenc.c > +++ b/libavcodec/libvpxenc.c > @@ -902,7 +902,17 @@ static void set_colorspace(AVCodecContext *avctx) > vpx_cs = ctx->vpx_cs; > } else { > switch (avctx->colorspace) { > - case AVCOL_SPC_RGB: vpx_cs = VPX_CS_SRGB; break; > + case AVCOL_SPC_RGB: > + // RGB pixel formats (GBRP, GBRP10, GBRP12) set ctx->vpx_cs > + // to VPX_CS_SRGB in set_pix_fmt() and take the branch above, > + // so reaching here means the pixel format is YUV with > + // incorrect RGB colorspace metadata.
What if the input is yuv444? In that case it could be holding rgb data. Profile 1 and 3 assume no subsampling when decoding sRGB content. > + av_log(avctx, AV_LOG_WARNING, > + "RGB colorspace is not compatible with pixel format %s, " > + "using BT.709 instead.\n", > + av_get_pix_fmt_name(avctx->pix_fmt)); > + vpx_cs = VPX_CS_BT_709; > + break; > case AVCOL_SPC_BT709: vpx_cs = VPX_CS_BT_709; break; > case AVCOL_SPC_UNSPECIFIED: vpx_cs = VPX_CS_UNKNOWN; break; > case AVCOL_SPC_RESERVED: vpx_cs = VPX_CS_RESERVED; break; > -- > 2.52.0 > > _______________________________________________ > ffmpeg-devel mailing list -- [email protected] > To unsubscribe send an email to [email protected] _______________________________________________ ffmpeg-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
