movenc: Make chapter track QuickTime compatible

QuickTime requires that the stsd.text box be completely filled in.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -2980,18 +2980,25 @@ static int mov_write_packet(AVFormatContext *s, AVPacket *pkt)
 
 // QuickTime chapters involve an additional text track with the chapter names
 // as samples, and a tref pointing from the other tracks to the chapter one.
-static void mov_create_chapter_track(AVFormatContext *s, int tracknum)
+static int mov_create_chapter_track(AVFormatContext *s, int tracknum)
 {
     MOVMuxContext *mov = s->priv_data;
     MOVTrack *track = &mov->tracks[tracknum];
     AVPacket pkt = { .stream_index = tracknum, .flags = AV_PKT_FLAG_KEY };
     int i, len;
+    // These properties are required to make QT recognize the chapter track
+    uint8_t chapter_properties[43] = { 0, 0, 0, 0, 0, 0, 0, 1, };
 
     track->mode = mov->mode;
     track->tag = MKTAG('t','e','x','t');
     track->timescale = MOV_TIMESCALE;
     track->enc = avcodec_alloc_context3(NULL);
     track->enc->codec_type = AVMEDIA_TYPE_SUBTITLE;
+    track->enc->extradata = av_malloc(sizeof(chapter_properties));
+    if (track->enc->extradata == NULL)
+        return AVERROR(ENOMEM);
+    track->enc->extradata_size = sizeof(chapter_properties);
+    memcpy(track->enc->extradata, chapter_properties, sizeof(chapter_properties));
 
     for (i = 0; i < s->nb_chapters; i++) {
         AVChapter *c = s->chapters[i];
@@ -3011,6 +3018,8 @@ static void mov_create_chapter_track(AVFormatContext *s, int tracknum)
             av_freep(&pkt.data);
         }
     }
+
+    return 0;
 }
 
 static int mov_write_header(AVFormatContext *s)
@@ -3379,8 +3388,10 @@ static int mov_write_trailer(AVFormatContext *s)
         mov_write_mfra_tag(pb, mov);
     }
 
-    if (mov->chapter_track)
+    if (mov->chapter_track) {
+        av_free(mov->tracks[mov->chapter_track].enc->extradata);
         av_freep(&mov->tracks[mov->chapter_track].enc);
+    }
 
     for (i = 0; i < mov->nb_streams; i++) {
         if (mov->tracks[i].tag == MKTAG('r','t','p',' '))