avformat/mov: make invalid sampledelta error more verbose

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

libavformat/mov.c

@@ -1927,7 +1927,8 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
         /* 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\n", sample_duration);
+            av_log(c->fc, AV_LOG_ERROR, "Invalid SampleDelta %d in STTS, at %d st:%d\n",
+                   sample_duration, i, c->fc->nb_streams-1);
             sample_duration = 1;
         }
         if (sample_count < 0) {