matroskadec: set a default duration also for packets comming from a simple block

libavformat/matroskadec.c

@@ -486,7 +486,7 @@ static EbmlSyntax matroska_segments[] = {
 static EbmlSyntax matroska_blockgroup[] = {
     { MATROSKA_ID_BLOCK,          EBML_BIN,  0, offsetof(MatroskaBlock,bin) },
     { MATROSKA_ID_SIMPLEBLOCK,    EBML_BIN,  0, offsetof(MatroskaBlock,bin) },
-    { MATROSKA_ID_BLOCKDURATION,  EBML_UINT, 0, offsetof(MatroskaBlock,duration), {.u=AV_NOPTS_VALUE} },
+    { MATROSKA_ID_BLOCKDURATION,  EBML_UINT, 0, offsetof(MatroskaBlock,duration) },
     { MATROSKA_ID_BLOCKREFERENCE, EBML_UINT, 0, offsetof(MatroskaBlock,reference) },
     { 1,                          EBML_UINT, 0, offsetof(MatroskaBlock,non_simple), {.u=1} },
     { 0 }
@@ -1622,7 +1622,7 @@ static int matroska_parse_block(MatroskaDemuxContext *matroska, uint8_t *data,
     st = track->stream;
     if (st->discard >= AVDISCARD_ALL)
         return res;
-    if (duration == AV_NOPTS_VALUE)
+    if (!duration)
         duration = track->default_duration / matroska->time_scale;
 
     block_time = AV_RB16(data);