Colorimetry normalize
The demux likes matroskademux could create such a caps:
video/x-vp9, width=(int)3840, height=(int)2160, framerate=(fraction)30000/1001, colorimetry=(string)2:3:0:0
The color transfer and primaries are unknown because its doesn't exist in the metadata. But that would stop the v4l2 vp9 decoder.
I think we need a new plugin here to strip the colorimetry or normalize it.