[FFmpeg-cvslog] avformat/matroskaenc: Don't use size of inexistent Cluster

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Wed Jan 22 20:01:30 2020 +0100| [4dd63ae86c311da269426803d440d907cd9f66a2] | committer: Andreas Rheinhardt

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 at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=4dd63ae86c311da269426803d440d907cd9f66a2
---

 libavformat/matroskaenc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 2cd5933da8..5e0346d341 100644
--- 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,