Drop code that attempts to decode frames that are prefixed by junk.

Too often it ends up decoding random data into noise without detecting
it (for example after seeking of some MP3 data with oddly often occurring
startcode emulation).
Fixes issue1154.

Originally committed as revision 19302 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegaudiodec.c

@@ -2255,20 +2255,15 @@ static int decode_frame(AVCodecContext * avctx,
     MPADecodeContext *s = avctx->priv_data;
     uint32_t header;
     int out_size;
-    int skipped = 0;
     OUT_INT *out_samples = data;
 
-retry:
     if(buf_size < HEADER_SIZE)
         return -1;
 
     header = AV_RB32(buf);
     if(ff_mpa_check_header(header) < 0){
-        buf++;
-        buf_size--;
-        skipped++;
-        av_log(avctx, AV_LOG_ERROR, "Header missing skipping one byte.\n");
-        goto retry;
+        av_log(avctx, AV_LOG_ERROR, "Header missing\n");
+        return -1;
     }
 
     if (ff_mpegaudio_decode_header((MPADecodeHeader *)s, header) == 1) {
@@ -2297,7 +2292,7 @@ retry:
     }else
         av_log(avctx, AV_LOG_DEBUG, "Error while decoding MPEG audio frame.\n"); //FIXME return -1 / but also return the number of bytes consumed
     s->frame_size = 0;
-    return buf_size + skipped;
+    return buf_size;
 }
 
 static void flush(AVCodecContext *avctx){