ac3dec: update checked AV_EF flags.

A user who wishes to use default error concealment cannot set the
AV_EF_CRCCHECK flag because not every CRC in every format is a
reliable indicator of bitstream damage. In some formats crcrs
can be nonsensical in absence of any damage. We thus add the
AV_EF_CAREFUL flag in addition to the AV_EF_CRCCHECK flag to
allow a user to enable this reliable CRC check without having to
enable all CRC checks in all formats.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ac3dec.c

@@ -1371,7 +1371,7 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data,
         if (s->frame_size > buf_size) {
             av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
             err = AAC_AC3_PARSE_ERROR_FRAME_SIZE;
-        } else if (avctx->err_recognition & AV_EF_CRCCHECK) {
+        } else if (avctx->err_recognition & (AV_EF_CRCCHECK|AV_EF_CAREFUL)) {
             /* check for crc mismatch */
             if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2],
                        s->frame_size - 2)) {