demux_lavf: add hack for stream-changing ogg input (internet radio)

Some internet radio streams are ogg/vorbis with a new stream for each
track (and the previous stream stops receiving data). Add a hack to
ignore the stream number in packets when input seems to match this
case; all packets will be effectively regarded as parts of the same
audio stream. This workaround can't work perfectly with current lavf
because it will keep adding streams and then hit its 20 stream
maximum; at that point playback will likely fail. Print a warning
about this problem and mention "-demuxer ogg" as a possible
workaround.

Currently there's no check that the vorbis extradata is actually
compatible between the streams.

1 files changed, 56 insertions, 1 deletions

diff --git a/libmpdemux/demux_lavf.c b/libmpdemux/demux_lavf.c
index ef4a20ae7f..8457c1d816 100644
--- a/libmpdemux/demux_lavf.c
+++ b/libmpdemux/demux_lavf.c
@@ -75,6 +75,7 @@ typedef struct lavf_priv {
     int sstreams[MAX_S_STREAMS];
     int cur_program;
     int nb_streams_last;
+    bool internet_radio_hack;
 }lavf_priv_t;
 
 static int mp_read(void *opaque, uint8_t *buf, int size) {
@@ -608,6 +609,58 @@ static demuxer_t* demux_open_lavf(demuxer_t *demuxer){
     return demuxer;
 }
 
+static void check_internet_radio_hack(struct demuxer *demuxer)
+{
+    struct lavf_priv *priv = demuxer->priv;
+    struct AVFormatContext *avfc = priv->avfc;
+
+    if (!matches_avinputformat_name(priv, "ogg"))
+        return;
+    if (priv->nb_streams_last == avfc->nb_streams)
+        return;
+    if (avfc->nb_streams - priv->nb_streams_last == 1
+        && priv->video_streams == 0 && priv->sub_streams == 0
+        && demuxer->a_streams[priv->audio_streams-1]->format == 0x566f // vorbis
+        && (priv->audio_streams == 2 || priv->internet_radio_hack)
+        && demuxer->a_streams[0]->format == 0x566f) {
+        // extradata match could be checked but would require parsing
+        // headers, as the comment section will vary
+        if (!priv->internet_radio_hack) {
+            mp_msg(MSGT_DEMUX, MSGL_V,
+                   "[lavf] enabling internet ogg radio hack\n");
+#if LIBAVFORMAT_VERSION_MAJOR < 53
+            mp_tmsg(MSGT_DEMUX, MSGL_WARN, "[lavf] This looks like an "
+                    "internet radio ogg stream with track changes.\n"
+                    "Playback will likely fail after %d track changes "
+                    "due to libavformat limitations.\n"
+                    "You may be able to work around that limitation by "
+                    "using -demuxer ogg.\n", MAX_STREAMS);
+#endif
+        }
+#if LIBAVFORMAT_VERSION_MAJOR < 53
+        if (avfc->nb_streams == MAX_STREAMS) {
+            mp_tmsg(MSGT_DEMUX, MSGL_WARN, "[lavf] This is the %dth "
+                    "track.\nPlayback will likely fail at the next change.\n"
+                    "You may be able to work around this limitation by "
+                    "using -demuxer ogg.\n", MAX_STREAMS);
+        }
+#endif
+        priv->internet_radio_hack = true;
+        // use new per-track metadata as global metadata
+        AVMetadataTag *t = NULL;
+        AVStream *stream = avfc->streams[avfc->nb_streams - 1];
+        while ((t = av_metadata_get(stream->metadata, "", t,
+                                   AV_METADATA_IGNORE_SUFFIX)))
+            demux_info_add(demuxer, t->key, t->value);
+    } else {
+        if (priv->internet_radio_hack)
+            mp_tmsg(MSGT_DEMUX, MSGL_WARN, "[lavf] Internet radio ogg hack "
+                    "was enabled, but stream characteristics changed.\n"
+                    "This may or may not work.\n");
+        priv->internet_radio_hack = false;
+    }
+}
+
 static int demux_lavf_fill_buffer(demuxer_t *demux, demux_stream_t *dsds){
     lavf_priv_t *priv= demux->priv;
     AVPacket pkt;
@@ -624,11 +677,13 @@ static int demux_lavf_fill_buffer(demuxer_t *demux, demux_stream_t *dsds){
     // handle any new streams that might have been added
     for (id = priv->nb_streams_last; id < priv->avfc->nb_streams; id++)
         handle_stream(demux, priv->avfc, id);
+    check_internet_radio_hack(demux);
+
     priv->nb_streams_last = priv->avfc->nb_streams;
 
     id= pkt.stream_index;
 
-    if(id==demux->audio->id){
+    if (id == demux->audio->id || priv->internet_radio_hack) {
         // audio
         ds=demux->audio;
         if(!ds->sh){