Do not scan for MP3 header after the given buffer and return skipped

bytes along with consumed bytes on successful decoding.
patch by Zdenek Kabelac, zdenek.kabelac gmail com

Originally committed as revision 18736 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegaudiodec.c

@@ -2263,6 +2263,7 @@ 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:
@@ -2272,7 +2273,8 @@ retry:
     header = AV_RB32(buf);
     if(ff_mpa_check_header(header) < 0){
         buf++;
-//        buf_size--;
+        buf_size--;
+        skipped++;
         av_log(avctx, AV_LOG_ERROR, "Header missing skipping one byte.\n");
         goto retry;
     }
@@ -2303,7 +2305,7 @@ 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;
+    return buf_size + skipped;
 }
 
 static void flush(AVCodecContext *avctx){