Encoder: HEVC: Add Packed SEI header support
@sree
Submitted by Sreerenj Balachandran Link to original bug (#766047)
Description
VA-backed driver might not insert SEI headers in to the encoded stream by itself. We are supposed to provide the SEI headers from upper layer. It is good provide buffering_period and picture_timing SEI headers as VAEncPackedHeaders while enabling CBR mode encode.