avformat/matroskaenc: Fix ReferenceBlock timestamp
authorAndreas Rheinhardt <andreas.rheinhardt@gmail.com>
Wed, 1 Jan 2020 00:58:18 +0000 (01:58 +0100)
committerJames Almer <jamrial@gmail.com>
Sat, 11 Jan 2020 14:18:58 +0000 (11:18 -0300)
In order to indicate that the frames in a BlockGroup are not keyframes,
one has to add a ReferenceBlock element containing the timestamp of a
referenced Block that has already been written. The timestamp ought to be
relative to the timestamp of the Block it is attached to. Yet the
Matroska muxer used the relative timestamp of the preceding Block of the
track, i.e. the timestamp of the preceding block relative to the
timestamp of the Cluster containing said block (that need not be the
Cluster containing the current Block). This has been fixed.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>
libavformat/matroskaenc.c

index 71c9afb..9534214 100644 (file)
@@ -2163,9 +2163,9 @@ static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,
         av_free(data);
 
     if (blockid == MATROSKA_ID_BLOCK && !keyframe) {
-        put_ebml_sint(pb, MATROSKA_ID_BLOCKREFERENCE, track->last_timestamp);
+        put_ebml_sint(pb, MATROSKA_ID_BLOCKREFERENCE, track->last_timestamp - ts);
     }
-    track->last_timestamp = ts - mkv->cluster_pts;
+    track->last_timestamp = ts;
 
     if (discard_padding) {
         put_ebml_sint(pb, MATROSKA_ID_DISCARDPADDING, discard_padding);