only check ac3 crc if AVCodecContext.error_resilience > 0

Originally committed as revision 11388 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ac3dec.c

@@ -1109,10 +1109,12 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
     }
 
     /* check for crc mismatch */
+    if(avctx->error_resilience > 0) {
     if(av_crc(av_crc8005, 0, &buf[2], s->frame_size-2)) {
         av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
         return -1;
     }
+    }
 
     avctx->sample_rate = s->sample_rate;
     avctx->bit_rate = s->bit_rate;