movenc: Add a separate start_pts

This fixes calculation of trackDuration if the MOVIentry array
is cleared. This is required by the fragmentation support in the
next patch.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -987,7 +987,7 @@ static int mov_write_stts_tag(AVIOContext *pb, MOVTrack *track)
         stts_entries = av_malloc(track->entry * sizeof(*stts_entries)); /* worst case */
         for (i=0; i<track->entry; i++) {
             int64_t duration = i + 1 == track->entry ?
-                track->trackDuration - track->cluster[i].dts + track->cluster[0].dts : /* readjusting */
+                track->trackDuration - track->cluster[i].dts + track->start_dts : /* readjusting */
                 track->cluster[i+1].dts - track->cluster[i].dts;
             if (i && duration == stts_entries[entries].duration) {
                 stts_entries[entries].count++; /* compress */
@@ -2104,7 +2104,9 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
     trk->cluster[trk->entry].size = size;
     trk->cluster[trk->entry].entries = samplesInChunk;
     trk->cluster[trk->entry].dts = pkt->dts;
-    trk->trackDuration = pkt->dts - trk->cluster[0].dts + pkt->duration;
+    if (trk->start_dts == AV_NOPTS_VALUE)
+        trk->start_dts = pkt->dts;
+    trk->trackDuration = pkt->dts - trk->start_dts + pkt->duration;
 
     if (pkt->pts == AV_NOPTS_VALUE) {
         av_log(s, AV_LOG_WARNING, "pts has no value\n");
@@ -2253,6 +2255,7 @@ static int mov_write_header(AVFormatContext *s)
         /* If hinting of this track is enabled by a later hint track,
          * this is updated. */
         track->hint_track = -1;
+        track->start_dts = AV_NOPTS_VALUE;
         if(st->codec->codec_type == AVMEDIA_TYPE_VIDEO){
             if (track->tag == MKTAG('m','x','3','p') || track->tag == MKTAG('m','x','3','n') ||
                 track->tag == MKTAG('m','x','4','p') || track->tag == MKTAG('m','x','4','n') ||

libavformat/movenc.h

@@ -89,6 +89,7 @@ typedef struct MOVIndex {
     int         height; ///< active picture (w/o VBI) height for D-10/IMX
     uint32_t    tref_tag;
     int         tref_id; ///< trackID of the referenced track
+    int64_t     start_dts;
 
     int         hint_track;   ///< the track that hints this track, -1 if no hint track is set
     int         src_track;    ///< the track that this hint track describes