mpeg12: fix logic that prevents extradata from being parsed twice.

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

libavcodec/mpeg12.c

@@ -2286,12 +2286,13 @@ static int mpeg_decode_frame(AVCodecContext *avctx,
 
     s->slice_count = 0;
 
-    if (avctx->extradata && !avctx->frame_number) {
+    if (avctx->extradata && !s->parsed_extra) {
         int ret = decode_chunks(avctx, picture, data_size, avctx->extradata, avctx->extradata_size);
         if(*data_size) {
             av_log(avctx, AV_LOG_ERROR, "picture in extradata\n");
             *data_size = 0;
         }
+        s->parsed_extra = 1;
         if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE))
             return ret;
     }

libavcodec/mpeg12.h

@@ -42,6 +42,7 @@ typedef struct Mpeg1Context {
     AVRational frame_rate_ext;       ///< MPEG-2 specific framerate modificator
     int sync;                        ///< Did we reach a sync point like a GOP/SEQ/KEYFrame?
     int tmpgexs;
+    int parsed_extra;
 } Mpeg1Context;
 
 extern uint8_t ff_mpeg12_static_rl_table_store[2][2][2*MAX_RUN + MAX_LEVEL + 3];