Lately we have implemented closed captions encoding for Intel MediaSDK boosted AVC Encoder. Everything works fine except one usage case.
When we have several closed captioning data (e.g. SCTE and ATSC captions), we should put them in different SEI. So we create to user data payloads: one for each CC data. When coding is progressive, everything is ok. But when coding is interlaced, encoder puts these SEI like this:
SEI (buffering period)
SEI (picture timing - top field)
SEI (user data registered - SCTE CC)
I SLICE Data (top field)
SEI (picture timing - bottom field)
SEI (user data - ATSC CC)
P SLICE Data (bottom field)
What should be done to put both SEI user data in the top field?