movdec: Try to recover from overreading atoms

Fixes Ticket1596
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mov.c

@@ -2666,6 +2666,10 @@ static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             left = a.size - avio_tell(pb) + start_pos;
             if (left > 0) /* skip garbage at atom end */
                 avio_skip(pb, left);
+            else if(left < 0) {
+                av_log(c->fc, AV_LOG_DEBUG, "undoing overread of %d in '%.4s'\n", -left, (char*)&a.type);
+                avio_seek(pb, left, SEEK_CUR);
+            }
         }
 
         total_size += a.size;