[FFmpeg-devel] [FFmpeg-cvslog] mpegaudiodec_template: disable CRC checking for layers 1 and 2

Lynne dev at lynne.ee
Mon Aug 3 11:18:53 EEST 2020


Aug 3, 2020, 08:58 by martin at martin.st:

> On Sun, 2 Aug 2020, Lynne wrote:
>
>> ffmpeg | branch: master | Lynne <dev at lynne.ee> | Sun Aug  2 22:45:00 2020 +0200| [b48397e7b84864f2d4c70361a4c4bed93e826753] | committer: Lynne
>>
>> mpegaudiodec_template: disable CRC checking for layers 1 and 2
>>
>> Layers 1 and 2 use lengths in bits which are not a multiple of 8,
>> and our CRC works on a per-byte basis.
>>
>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b48397e7b84864f2d4c70361a4c4bed93e826753
>>>
>> ---
>>
>> libavcodec/mpegaudiodec_template.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/mpegaudiodec_template.c b/libavcodec/mpegaudiodec_template.c
>> index 3d7e3ba4f2..f03d7bc275 100644
>> --- a/libavcodec/mpegaudiodec_template.c
>> +++ b/libavcodec/mpegaudiodec_template.c
>> @@ -1566,7 +1566,7 @@ static int mp_decode_frame(MPADecodeContext *s, OUT_INT **samples,
>>
>>  init_get_bits(&s->gb, buf + HEADER_SIZE, (buf_size - HEADER_SIZE) * 8);
>>
>> -    if (s->error_protection) {
>> +    if (s->error_protection && s->layer == 3) {
>>  uint16_t crc = get_bits(&s->gb, 16);
>>  if (s->err_recognition & AV_EF_CRCCHECK) {
>>  const int sec_len = s->lsf ? ((s->nb_channels == 1) ? 9  : 17) :
>>
>
> This change broke two fate tests; fate-h264-skip-nokey and fate-h264-skip-nointra. The change does look sensible in itself though (framecrcs that used to be all zeros now have nonzero, varying values).
>

Someone must have regen'd those tests after the patch was applied and thought
they were failing due to other changes.


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