[FFmpeg-devel] [PATCH v2 1/2] Parse ogg/flac header again after processing a new chained ogg bitstream.

[Romain Beauxis]

This patch makes sure that ogg/flac headers are parsed again when
encountering a new logic stream inside a chained ogg bistream[1].

This patches makes it possible to retrieve metadata in chained ogg/flac
bitstreams. It is particularly important because ogg/flac is one of the
only (if not the only one) lossless container supported over HTTP/icecast.

The patch has been tested with various ogg/flac encoders and appears to
work fine with ffmpeg.

Changes since last version:
* Make sure to clear the stream's metadata before parsing again.

1: https://xiph.org/ogg/doc/oggstream.html

---
 libavformat/oggdec.c       | 7 +++++--
 libavformat/oggparseflac.c | 2 ++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/libavformat/oggdec.c b/libavformat/oggdec.c
index 5339fdd32c..d986e19817 100644
--- a/libavformat/oggdec.c
+++ b/libavformat/oggdec.c
@@ -239,8 +239,11 @@ static int ogg_replace_stream(AVFormatContext *s, uint32_t serial, char *magic,
     os->start_trimming = 0;
     os->end_trimming = 0;
 
-    /* Chained files have extradata as a new packet */
-    if (codec == &ff_opus_codec)
+    /* Parse opus and flac header on new chained bitstream.
+     * For opus, header contains required extradata as new packet
+     * For both formats, this makes it possible to read chained metadata. */
+    if (codec == &ff_opus_codec ||
+        codec == &ff_flac_codec)
         os->header = -1;
 
     return i;
diff --git a/libavformat/oggparseflac.c b/libavformat/oggparseflac.c
index f25ed9cc15..932907fa1a 100644
--- a/libavformat/oggparseflac.c
+++ b/libavformat/oggparseflac.c
@@ -72,6 +72,8 @@ flac_header (AVFormatContext * s, int idx)
 
         avpriv_set_pts_info(st, 64, 1, samplerate);
     } else if (mdt == FLAC_METADATA_TYPE_VORBIS_COMMENT) {
+        /* New metadata packet; release old data. */
+        av_dict_free(&st->metadata);
         ff_vorbis_stream_comment(s, st, os->buf + os->pstart + 4, os->psize - 4);
     }
 
-- 
2.39.5 (Apple Git-154)