movenc: Support writing multiple trun atoms

This is needed if all the data for one track isn't continuous
within the mdat. Normally we make sure all the data for one
track is continuous, but in new cases we will need to have
the samples interleaved.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -2476,18 +2476,19 @@ static int mov_write_tfhd_tag(AVIOContext *pb, MOVMuxContext *mov,
 }
 
 static int mov_write_trun_tag(AVIOContext *pb, MOVMuxContext *mov,
-                              MOVTrack *track, int moof_size)
+                              MOVTrack *track, int moof_size,
+                              int first, int end)
 {
     int64_t pos = avio_tell(pb);
     uint32_t flags = MOV_TRUN_DATA_OFFSET;
     int i;
 
-    for (i = 0; i < track->entry; i++) {
+    for (i = first; i < end; i++) {
         if (get_cluster_duration(track, i) != track->default_duration)
             flags |= MOV_TRUN_SAMPLE_DURATION;
         if (track->cluster[i].size != track->default_size)
             flags |= MOV_TRUN_SAMPLE_SIZE;
-        if (i > 0 && get_sample_flags(track, &track->cluster[i]) != track->default_sample_flags)
+        if (i > first && get_sample_flags(track, &track->cluster[i]) != track->default_sample_flags)
             flags |= MOV_TRUN_SAMPLE_FLAGS;
     }
     if (!(flags & MOV_TRUN_SAMPLE_FLAGS) && track->entry > 0 &&
@@ -2501,18 +2502,18 @@ static int mov_write_trun_tag(AVIOContext *pb, MOVMuxContext *mov,
     avio_w8(pb, 0); /* version */
     avio_wb24(pb, flags);
 
-    avio_wb32(pb, track->entry); /* sample count */
+    avio_wb32(pb, end - first); /* sample count */
     if (mov->flags & FF_MOV_FLAG_OMIT_TFHD_OFFSET &&
         !(mov->flags & FF_MOV_FLAG_DEFAULT_BASE_MOOF) &&
         !mov->first_trun)
         avio_wb32(pb, 0); /* Later tracks follow immediately after the previous one */
     else
         avio_wb32(pb, moof_size + 8 + track->data_offset +
-                      track->cluster[0].pos); /* data offset */
+                      track->cluster[first].pos); /* data offset */
     if (flags & MOV_TRUN_FIRST_SAMPLE_FLAGS)
-        avio_wb32(pb, get_sample_flags(track, &track->cluster[0]));
+        avio_wb32(pb, get_sample_flags(track, &track->cluster[first]));
 
-    for (i = 0; i < track->entry; i++) {
+    for (i = first; i < end; i++) {
         if (flags & MOV_TRUN_SAMPLE_DURATION)
             avio_wb32(pb, get_cluster_duration(track, i));
         if (flags & MOV_TRUN_SAMPLE_SIZE)
@@ -2652,13 +2653,20 @@ static int mov_write_traf_tag(AVIOContext *pb, MOVMuxContext *mov,
                               int moof_size)
 {
     int64_t pos = avio_tell(pb);
+    int i, start = 0;
     avio_wb32(pb, 0); /* size placeholder */
     ffio_wfourcc(pb, "traf");
 
     mov_write_tfhd_tag(pb, mov, track, moof_offset);
     if (mov->mode != MODE_ISM)
         mov_write_tfdt_tag(pb, track);
-    mov_write_trun_tag(pb, mov, track, moof_size);
+    for (i = 1; i < track->entry; i++) {
+        if (track->cluster[i].pos != track->cluster[i - 1].pos + track->cluster[i - 1].size) {
+            mov_write_trun_tag(pb, mov, track, moof_size, start, i);
+            start = i;
+        }
+    }
+    mov_write_trun_tag(pb, mov, track, moof_size, start, track->entry);
     if (mov->mode == MODE_ISM) {
         mov_write_tfxd_tag(pb, track);