mov: Set negative Sample_duration in STTS to 1

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mov.c

@@ -1471,6 +1471,11 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
         sample_count=avio_rb32(pb);
         sample_duration = avio_rb32(pb);
+        /* sample_duration < 0 is invalid based on the spec */
+        if (sample_duration < 0) {
+            av_log(c->fc, AV_LOG_ERROR, "Invalid SampleDelta in STTS %d", sample_duration);
+            sample_duration = 1;
+        }
         sc->stts_data[i].count= sample_count;
         sc->stts_data[i].duration= sample_duration;