vorbis: extract metadata from the middle of a stream

If a special comment packet shows up in the middle of the stream, we
should extract it out into the vorbis stream metadata dictionary.

Also, if there is metadata in the packet on the way in, it might linger
since we only add data to the dictionary causing stale metadata to be
inserted into the stream. Instead, clear it to remove any doubt about
what is new and old.
Signed-off-by: Ben Boeckel <mathstuf@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/oggparsevorbis.c

@@ -242,6 +242,36 @@ static void vorbis_cleanup(AVFormatContext *s, int idx)
             av_freep(&priv->packet[i]);
 }
 
+static int vorbis_update_metadata(AVFormatContext *s, int idx)
+{
+    struct ogg *ogg = s->priv_data;
+    struct ogg_stream *os = ogg->streams + idx;
+    AVStream *st = s->streams[idx];
+    int ret;
+
+    if (os->psize <= 8)
+        return 0;
+
+    /* New metadata packet; release old data. */
+    av_dict_free(&st->metadata);
+    ret = ff_vorbis_comment(s, &st->metadata, os->buf + os->pstart + 7,
+                            os->psize - 8);
+    if (ret < 0)
+        return ret;
+
+    /* Update the metadata if possible. */
+    av_freep(&os->new_metadata);
+    if (st->metadata) {
+        os->new_metadata = av_packet_pack_dictionary(st->metadata, &os->new_metadata_size);
+    /* Send an empty dictionary to indicate that metadata has been cleared. */
+    } else {
+        os->new_metadata = av_malloc(1);
+        os->new_metadata_size = 0;
+    }
+
+    return ret;
+}
+
 static int vorbis_header(AVFormatContext *s, int idx)
 {
     struct ogg *ogg = s->priv_data;
@@ -317,9 +347,7 @@ static int vorbis_header(AVFormatContext *s, int idx)
             avpriv_set_pts_info(st, 64, 1, srate);
         }
     } else if (os->buf[os->pstart] == 3) {
-        if (os->psize > 8 &&
-            ff_vorbis_comment(s, &st->metadata, os->buf + os->pstart + 7,
-                              os->psize - 8) >= 0) {
+        if (vorbis_update_metadata(s, idx) >= 0) {
             // drop all metadata we parsed and which is not required by libvorbis
             unsigned new_len = 7 + 4 + AV_RL32(priv->packet[1] + 7) + 4 + 1;
             if (new_len >= 16 && new_len < os->psize) {
@@ -350,7 +378,7 @@ static int vorbis_packet(AVFormatContext *s, int idx)
     struct ogg *ogg = s->priv_data;
     struct ogg_stream *os = ogg->streams + idx;
     struct oggvorbis_private *priv = os->private;
-    int duration;
+    int duration, flags = 0;
 
     /* first packet handling
      * here we parse the duration of each packet in the first page and compare
@@ -364,19 +392,25 @@ static int vorbis_packet(AVFormatContext *s, int idx)
         avpriv_vorbis_parse_reset(&priv->vp);
         duration = 0;
         seg = os->segp;
-        d = avpriv_vorbis_parse_frame(&priv->vp, last_pkt, 1);
+        d = avpriv_vorbis_parse_frame_flags(&priv->vp, last_pkt, 1, &flags);
         if (d < 0) {
             os->pflags |= AV_PKT_FLAG_CORRUPT;
             return 0;
+        } else if (flags & VORBIS_FLAG_COMMENT) {
+            vorbis_update_metadata(s, idx);
+            flags = 0;
         }
         duration += d;
         last_pkt = next_pkt =  next_pkt + os->psize;
         for (; seg < os->nsegs; seg++) {
             if (os->segments[seg] < 255) {
-                int d = avpriv_vorbis_parse_frame(&priv->vp, last_pkt, 1);
+                int d = avpriv_vorbis_parse_frame_flags(&priv->vp, last_pkt, 1, &flags);
                 if (d < 0) {
                     duration = os->granule;
                     break;
+                } else if (flags & VORBIS_FLAG_COMMENT) {
+                    vorbis_update_metadata(s, idx);
+                    flags = 0;
                 }
                 duration += d;
                 last_pkt  = next_pkt + os->segments[seg];
@@ -396,10 +430,13 @@ static int vorbis_packet(AVFormatContext *s, int idx)
 
     /* parse packet duration */
     if (os->psize > 0) {
-        duration = avpriv_vorbis_parse_frame(&priv->vp, os->buf + os->pstart, 1);
+        duration = avpriv_vorbis_parse_frame_flags(&priv->vp, os->buf + os->pstart, 1, &flags);
         if (duration < 0) {
             os->pflags |= AV_PKT_FLAG_CORRUPT;
             return 0;
+        } else if (flags & VORBIS_FLAG_COMMENT) {
+            vorbis_update_metadata(s, idx);
+            flags = 0;
         }
         os->pduration = duration;
     }