Merge commit '31931520'

* commit '31931520':
  mov: Do not allow updating the time scale after it has been set
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mov.c

@@ -836,6 +836,11 @@ static int mov_read_mdhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     st = c->fc->streams[c->fc->nb_streams-1];
     sc = st->priv_data;
 
+    if (sc->time_scale) {
+        av_log(c->fc, AV_LOG_ERROR, "Multiple mdhd?\n");
+        return AVERROR_INVALIDDATA;
+    }
+
     version = avio_r8(pb);
     if (version > 1) {
         avpriv_request_sample(c->fc, "Version %d", version);