avformat/matroskaenc: Add check for using explicit TrackNumber

When creating DASH streams, the TrackNumber is externally prescribed
and not derived from the number of streams in the AVFormatContext, so
if the number of tracks for a file using an explicit TrackNumber was
more than one, the resulting file would be broken (it would be impossible
to tell to which track a Block belongs if different tracks share the
same TrackNumber). So disallow this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index a65221e14376b865b2dd85ed4beb0659703e35a6..2cd5933da8633d3b6c337fcb77ae4524003f9e45 100644 (file)
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -2650,6 +2650,9 @@ static int mkv_init(struct AVFormatContext *s)
         track->track_num_size = ebml_num_size(track->track_num);
     }
 
+    if (mkv->is_dash && nb_tracks != 1)
+        return AVERROR(EINVAL);
+
     return 0;
 }