"HEVC HDR UHDTV Bitstreams using HLG10 shall also contain the
alternative_transfer_characteristics SEI message. The
alternative_transfer_characteristics SEI message shall be inserted on
the HEVC DVB_RAP, and preferred_transfer_characteristics shall be set
equal to "18", indicating Recommendation ITU-R BT. 2100 [45] HLG
system."
Signed-off-by: Zhong Li <zhongli_dev@126.com>