avformat/matroskaenc: Don't use size of inexistent Cluster

In order to determine whether the current Cluster needs to be closed
because of the limits on clustersize and clustertime,
mkv_write_packet() would first get the size of the current Cluster by
applying avio_tell() on the dynamic buffer holding the current Cluster.
It did this without checking whether there is a dynamic buffer for
writing Clusters open right now.

In this case (which happens when writing the first packet)
avio_tell() returned AVERROR(EINVAL); yet it is not good to rely on
avio_tell() (or actually, avio_seek()) to handle the situation
gracefully.

Fixing this is easy: Only check whether a Cluster needs to be closed
if a Cluster is in fact open.

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

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 2cd5933da8633d3b6c337fcb77ae4524003f9e45..5e0346d34137a5028c4925969c3164267c9f0d85 100644 (file)
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -2332,6 +2332,7 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
     if (ret < 0)
         return ret;
 
+    if (mkv->cluster_pos != -1) {
     if (mkv->tracks[pkt->stream_index].write_dts)
         cluster_time = pkt->dts - mkv->cluster_pts;
     else
@@ -2359,9 +2360,10 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
         start_new_cluster = 0;
     }
 
-    if (mkv->cluster_pos != -1 && start_new_cluster) {
+    if (start_new_cluster) {
         mkv_end_cluster(s);
     }
+    }
 
     if (!mkv->cluster_pos)
         avio_write_marker(s->pb,