lavf/mov.c: Correct keyframe search in edit list to return the very first...

lavf/mov.c: Correct keyframe search in edit list to return the very first keyframe/frame with matching timestamp. Fixes ticket#5904
Signed-off-by: Sasi Inguva <isasi@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -2847,11 +2847,23 @@ static int64_t find_prev_closest_index(AVStream *st,
     AVIndexEntry *e_keep = st->index_entries;
     int nb_keep = st->nb_index_entries;
     int64_t found = -1;
+    int64_t i = 0;
 
     st->index_entries = e_old;
     st->nb_index_entries = nb_old;
     found = av_index_search_timestamp(st, timestamp, flag | AVSEEK_FLAG_BACKWARD);
 
+    // Keep going backwards in the index entries until the timestamp is the same.
+    if (found >= 0) {
+        for (i = found; i > 0 && e_old[i].timestamp == e_old[i - 1].timestamp;
+             i--) {
+            if ((flag & AVSEEK_FLAG_ANY) ||
+                (e_old[i - 1].flags & AVINDEX_KEYFRAME)) {
+                found = i - 1;
+            }
+        }
+    }
+
     /* restore AVStream state*/
     st->index_entries = e_keep;
     st->nb_index_entries = nb_keep;