movenc: Handle need for extra packets to express subtitle duration.

As packet duration is not stored inherently in MPEG4 containers,
subtitles have their duration expressed by storing an additional
empty packet with a pts matching the desired end time of the real
subtitle. Additionally, it is generally expected that all streams
start at time = 0, so an empty packet needs to be inserted at the
beginning of the stream, before the first real subtitle.

Unfortunately, ffmpeg lacks a proper way to express that a subtitle
might map to multiple packets, so the muxer is the only place we
can handle this.

Signed-off-by: Philip Langdale <philipl@overt.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/libavformat/movenc.h b/libavformat/movenc.h
index 557bcda636..72427d8cfd 100644
--- a/libavformat/movenc.h
+++ b/libavformat/movenc.h
@@ -80,6 +80,7 @@ typedef struct MOVIndex {
     unsigned    timescale;
     uint64_t    time;
     int64_t     track_duration;
+    int         last_sample_is_subtitle_end;
     long        sample_count;
     long        sample_size;
     long        chunkCount;