Index: libavformat/matroskadec.c
===================================================================
--- libavformat/matroskadec.c	(Revision 21651)
+++ libavformat/matroskadec.c	(Arbeitskopie)
@@ -1383,6 +1383,8 @@
             st->codec->codec_type = CODEC_TYPE_AUDIO;
             st->codec->sample_rate = track->audio.out_samplerate;
             st->codec->channels = track->audio.channels;
+            if (st->codec->codec_id == CODEC_ID_AC3)
+                st->need_parsing = AVSTREAM_PARSE_HEADERS;
         } else if (track->type == MATROSKA_TRACK_TYPE_SUBTITLE) {
             st->codec->codec_type = CODEC_TYPE_SUBTITLE;
         }