Merge remote-tracking branch 'qatar/release/0.5' into release/0.5

* qatar/release/0.5:
  mpeg12: do not decode extradata more than once.

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

libavcodec/mpeg12.c

@@ -1163,6 +1163,7 @@ typedef struct Mpeg1Context {
     int save_width, save_height;
     AVRational frame_rate_ext;       ///< MPEG-2 specific framerate modificator
 
+    int extradata_decoded;
 } Mpeg1Context;
 
 static av_cold int mpeg_decode_init(AVCodecContext *avctx)
@@ -2299,8 +2300,10 @@ static int mpeg_decode_frame(AVCodecContext *avctx,
 
     s->slice_count= 0;
 
-    if(avctx->extradata && !avctx->frame_number)
+    if (avctx->extradata && !s->extradata_decoded) {
         decode_chunks(avctx, picture, data_size, avctx->extradata, avctx->extradata_size);
+        s->extradata_decoded = 1;
+    }
 
     return decode_chunks(avctx, picture, data_size, buf, buf_size);
 }