diff --git a/libavformat/demux.c b/libavformat/demux.c
index 4e983f0703..3cc48fd49e 100644
--- a/libavformat/demux.c
+++ b/libavformat/demux.c
@@ -1265,7 +1265,7 @@ static int parse_packet(AVFormatContext *s, AVPacket *pkt,
         /* set the duration */
         out_pkt->duration = (sti->parser->flags & PARSER_FLAG_COMPLETE_FRAMES) ? pkt->duration : 0;
         if (st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
-            if (sti->avctx->sample_rate > 0 && sti->parser->duration > 0) {
+            if (sti->avctx->sample_rate > 0 && !out_pkt->duration && sti->parser->duration > 0) {
                 out_pkt->duration =
                     av_rescale_q_rnd(sti->parser->duration,
                                      (AVRational) { 1, sti->avctx->sample_rate },
diff --git a/tests/ref/fate/matroska-encoding-delay b/tests/ref/fate/matroska-encoding-delay
index cfa1675b94..31d00882a4 100644
--- a/tests/ref/fate/matroska-encoding-delay
+++ b/tests/ref/fate/matroska-encoding-delay
@@ -21,7 +21,7 @@ ece637ed28526724c88f5c69b8bf7d6f *tests/data/fate/matroska-encoding-delay.matros
 1,         86,         86,       24,     1152, 0xc9e85398
 1,        110,        110,       24,     1152, 0xda1287d3
 0,        120,        120,       40,   238290, 0xbe18b18f
-1,        134,        134,       24,     1152, 0x1c9a6102
+1,        134,        134,       16,     1152, 0x1c9a6102
 [PACKET]
 codec_type=audio
 stream_index=1
diff --git a/tests/ref/fate/matroska-flac-channel-mapping b/tests/ref/fate/matroska-flac-channel-mapping
index 25627d6570..91a778853f 100644
--- a/tests/ref/fate/matroska-flac-channel-mapping
+++ b/tests/ref/fate/matroska-flac-channel-mapping
@@ -16,16 +16,16 @@
 1,       4096,       4096,     4096,       26, 0x50d30416
 0,       8192,       8192,     4096,       26, 0x51ee046f
 1,       8192,       8192,     4096,       26, 0x51ee046f
-0,      12288,      12288,     4096,       26, 0x521d0458
-1,      12288,      12288,     4096,       26, 0x521d0458
+0,      12288,      12288,     4097,       26, 0x521d0458
+1,      12288,      12288,     4097,       26, 0x521d0458
 0,      16385,      16385,     4096,       26, 0x531c043d
 1,      16385,      16385,     4096,       26, 0x531c043d
 0,      20481,      20481,     4096,       26, 0x53cf0442
 1,      20481,      20481,     4096,       26, 0x53cf0442
 0,      24577,      24577,     4096,       26, 0x536a0473
 1,      24577,      24577,     4096,       26, 0x536a0473
-0,      28673,      28673,     4096,       26, 0x5321046c
-1,      28673,      28673,     4096,       26, 0x5321046c
+0,      28673,      28673,     4097,       26, 0x5321046c
+1,      28673,      28673,     4097,       26, 0x5321046c
 0,      32770,      32770,     4096,       26, 0x51b00449
 1,      32770,      32770,     4096,       26, 0x51b00449
 0,      36866,      36866,     4096,       26, 0x518b042e