PREROLL_TIME      289 libavformat/asfenc.c     duration = asf->duration + PREROLL_TIME * 10000;
PREROLL_TIME      322 libavformat/asfenc.c     put_le64(pb, PREROLL_TIME); /* start time stamp */
PREROLL_TIME      721 libavformat/asfenc.c             put_payload_header(s, stream, timestamp+PREROLL_TIME, m_obj_size, m_obj_offset, payload_len, flags);