codec_private() hardcoded 8-bit 4:2:0 in the hvcC fixed header, wrong for
10-bit Main 10 UHD (essentially all UHD). Parse chroma_format_idc and
bit_depth_luma/chroma_minus8 from the SPS RBSP (with emulation-prevention
removal and sub-layer profile_tier_level handling) and emit the real
values; fall back to 8-bit 4:2:0 only if the SPS can't be parsed.
Also guard the 16-bit NAL length fields: a param set larger than 65535
bytes would truncate the length while appending all bytes, mis-framing
the record. Return None instead of emitting a corrupt hvcC.
MattJackson
2eee777b8f