H264HeadersBitstream::GetSliceHeaderPart1/GetSliceHeaderPart2 doesn't process colour_plane_id field of slice_header() syntax element.
Thanks for your report. I will forward the engineer owner.
ok, thank you!
some more investigation result from our engineering site: YUV444 is format that is not supported by the UMC H264 format. This element is relevant only for YUV444 streams, that is why it not included now.