movenc: Buffer the mdat for the initial moov fragment, too

This allows writing QuickTime-compatible fragmented mp4 (with
a non-empty moov atom) to a non-seekable output.

This buffers the mdat for the initial fragment just as it does
for all normal fragments, too. Previously, the resulting
atom structure was mdat,moov, moof,mdat ..., while it now
is moov,mdat, moof,mdat.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -96,9 +96,9 @@ static int mov_write_stco_tag(AVIOContext *pb, MOVTrack *track)
     avio_wb32(pb, track->entry); /* entry count */
     for (i=0; i<track->entry; i++) {
         if(mode64 == 1)
-            avio_wb64(pb, track->cluster[i].pos);
+            avio_wb64(pb, track->cluster[i].pos + track->data_offset);
         else
-            avio_wb32(pb, track->cluster[i].pos);
+            avio_wb32(pb, track->cluster[i].pos + track->data_offset);
     }
     return update_size(pb, pos);
 }
@@ -2681,6 +2681,10 @@ static int mov_flush_fragment(AVFormatContext *s)
 
     if (!(mov->flags & FF_MOV_FLAG_EMPTY_MOOV) && mov->fragments == 0) {
         int64_t pos = avio_tell(s->pb);
+        int ret;
+        AVIOContext *moov_buf;
+        uint8_t *buf;
+        int buf_size;
 
         for (i = 0; i < mov->nb_streams; i++)
             if (!mov->tracks[i].entry)
@@ -2688,10 +2692,24 @@ static int mov_flush_fragment(AVFormatContext *s)
         /* Don't write the initial moov unless all tracks have data */
         if (i < mov->nb_streams)
             return 0;
-        avio_seek(s->pb, mov->mdat_pos, SEEK_SET);
-        avio_wb32(s->pb, mov->mdat_size + 8);
-        avio_seek(s->pb, pos, SEEK_SET);
+
+        if ((ret = avio_open_dyn_buf(&moov_buf)) < 0)
+            return ret;
+        mov_write_moov_tag(moov_buf, mov, s);
+        buf_size = avio_close_dyn_buf(moov_buf, &buf);
+        av_free(buf);
+        for (i = 0; i < mov->nb_streams; i++)
+            mov->tracks[i].data_offset = pos + buf_size + 8;
+
         mov_write_moov_tag(s->pb, mov, s);
+
+        buf_size = avio_close_dyn_buf(mov->mdat_buf, &buf);
+        mov->mdat_buf = NULL;
+        avio_wb32(s->pb, buf_size + 8);
+        ffio_wfourcc(s->pb, "mdat");
+        avio_write(s->pb, buf, buf_size);
+        av_free(buf);
+
         mov->fragments++;
         mov->mdat_size = 0;
         for (i = 0; i < mov->nb_streams; i++) {
@@ -2804,13 +2822,21 @@ static int mov_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
         mov_flush_fragment(s);
     }
 
-    if (mov->flags & FF_MOV_FLAG_FRAGMENT && mov->fragments > 0) {
-        if (!trk->mdat_buf) {
-            int ret;
-            if ((ret = avio_open_dyn_buf(&trk->mdat_buf)) < 0)
-                return ret;
+    if (mov->flags & FF_MOV_FLAG_FRAGMENT) {
+        int ret;
+        if (mov->fragments > 0) {
+            if (!trk->mdat_buf) {
+                if ((ret = avio_open_dyn_buf(&trk->mdat_buf)) < 0)
+                    return ret;
+            }
+            pb = trk->mdat_buf;
+        } else {
+            if (!mov->mdat_buf) {
+                if ((ret = avio_open_dyn_buf(&mov->mdat_buf)) < 0)
+                    return ret;
+            }
+            pb = mov->mdat_buf;
         }
-        pb = trk->mdat_buf;
     }
 
     if (enc->codec_id == CODEC_ID_AMR_NB) {
@@ -2972,11 +2998,18 @@ static int mov_write_header(AVFormatContext *s)
     AVDictionaryEntry *t;
     int i, hint_track = 0;
 
-    /* Non-seekable output is ok if EMPTY_MOOV is set, or if using the ismv
-     * format (which sets EMPTY_MOOV later in this function). If ism_lookahead
+    /* Set the FRAGMENT flag if any of the fragmentation methods are
+     * enabled. */
+    if (mov->max_fragment_duration || mov->max_fragment_size ||
+        mov->flags & (FF_MOV_FLAG_EMPTY_MOOV |
+                      FF_MOV_FLAG_FRAG_KEYFRAME |
+                      FF_MOV_FLAG_FRAG_CUSTOM))
+        mov->flags |= FF_MOV_FLAG_FRAGMENT;
+
+    /* Non-seekable output is ok if using fragmentation. If ism_lookahead
      * is enabled, we don't support non-seekable output at all. */
     if (!s->pb->seekable &&
-        ((!(mov->flags & FF_MOV_FLAG_EMPTY_MOOV) &&
+        ((!(mov->flags & FF_MOV_FLAG_FRAGMENT) &&
           !(s->oformat && !strcmp(s->oformat->name, "ismv")))
          || mov->ism_lookahead)) {
         av_log(s, AV_LOG_ERROR, "muxer does not support non seekable output\n");
@@ -3116,18 +3149,11 @@ static int mov_write_header(AVFormatContext *s)
                             FF_MOV_FLAG_FRAG_CUSTOM)) &&
             !mov->max_fragment_duration && !mov->max_fragment_size)
             mov->max_fragment_duration = 5000000;
-        mov->flags |= FF_MOV_FLAG_EMPTY_MOOV | FF_MOV_FLAG_SEPARATE_MOOF;
+        mov->flags |= FF_MOV_FLAG_EMPTY_MOOV | FF_MOV_FLAG_SEPARATE_MOOF |
+                      FF_MOV_FLAG_FRAGMENT;
     }
 
-    /* Set the FRAGMENT flag if any of the fragmentation methods are
-     * enabled. */
-    if (mov->max_fragment_duration || mov->max_fragment_size ||
-        mov->flags & (FF_MOV_FLAG_EMPTY_MOOV |
-                      FF_MOV_FLAG_FRAG_KEYFRAME |
-                      FF_MOV_FLAG_FRAG_CUSTOM))
-        mov->flags |= FF_MOV_FLAG_FRAGMENT;
-
-    if (!(mov->flags & FF_MOV_FLAG_EMPTY_MOOV))
+    if (!(mov->flags & FF_MOV_FLAG_FRAGMENT))
         mov_write_mdat_tag(pb, mov);
 
     if (t = av_dict_get(s->metadata, "creation_time", NULL, 0))

libavformat/movenc.h

@@ -151,6 +151,7 @@ typedef struct MOVMuxContext {
     int max_fragment_duration;
     int max_fragment_size;
     int ism_lookahead;
+    AVIOContext *mdat_buf;
 } MOVMuxContext;
 
 #define FF_MOV_FLAG_RTP_HINT 1