uint8_t * extradata
some codecs need / can use extradata like Huffman tables.
main external API structure.
int ff_ass_add_rect(AVSubtitle *sub, const char *dialog, int ts_start, int ts_end, int raw)
Add an ASS dialog line to an AVSubtitle as a new AVSubtitleRect.
uint8_t * subtitle_header
Header containing style information for text subtitles.