8 Mar 2019, 17:48 by d...@lynne.ee: > > > > 7 Mar 2019, 21:18 by > mich...@niedermayer.cc > <mailto:mich...@niedermayer.cc>> : > >> On Wed, Mar 06, 2019 at 07:09:52PM +0100, Lynne wrote: >> >>> A lot of files have CRC included. >>> The CRC only covers 34 bytes at most from the frame but it should still be >>> enough for some amount of error detection. >>> >>> mpegaudiodec_template.c | 20 +++++++++++++++++--- >>> 1 file changed, 17 insertions(+), 3 deletions(-) >>> e8276f62fa92aa3f78e53b182b4ca7a2a460754c >>> 0001-mpegaudiodec_template-add-ability-to-check-CRC.patch >>> From e1f4410f35d3d7f774a0de59ab72764033d14900 Mon Sep 17 00:00:00 2001 >>> From: Lynne <>> >>> d...@lynne.ee <mailto:d...@lynne.ee>>>> <mailto:>>> >>> d...@lynne.ee <mailto:d...@lynne.ee>>>> >>> > >>> Date: Wed, 6 Mar 2019 17:04:04 +0000 >>> Subject: [PATCH] mpegaudiodec_template: add ability to check CRC >>> >>> A lot of files have CRC included. >>> The CRC only covers 34 bytes at most from the frame but it should still be >>> enough for some amount of error detection. >>> --- >>> libavcodec/mpegaudiodec_template.c | 20 +++++++++++++++++--- >>> 1 file changed, 17 insertions(+), 3 deletions(-) >>> >>> diff --git a/libavcodec/mpegaudiodec_template.c >>> b/libavcodec/mpegaudiodec_template.c >>> index 9cce88e263..0881b60bf5 100644 >>> --- a/libavcodec/mpegaudiodec_template.c >>> +++ b/libavcodec/mpegaudiodec_template.c >>> @@ -27,6 +27,7 @@ >>> #include "libavutil/attributes.h" >>> #include "libavutil/avassert.h" >>> #include "libavutil/channel_layout.h" >>> +#include "libavutil/crc.h" >>> #include "libavutil/float_dsp.h" >>> #include "libavutil/libm.h" >>> #include "avcodec.h" >>> @@ -1565,9 +1566,22 @@ static int mp_decode_frame(MPADecodeContext *s, >>> OUT_INT **samples, >>> >>> init_get_bits(&s->gb, buf + HEADER_SIZE, (buf_size - HEADER_SIZE) * 8); >>> >>> - /* skip error protection field */ >>> - if (s->error_protection) >>> - skip_bits(&s->gb, 16); >>> + if (s->error_protection) { >>> + 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) >>> : >>> + ((s->nb_channels == 1) ? 17 : 32); >>> + const AVCRC *crc_tab = av_crc_get_table(AV_CRC_16_ANSI); >>> + uint32_t crc_cal = av_crc(crc_tab, UINT16_MAX, &buf[2], 2); >>> + crc_cal = av_crc(crc_tab, crc_cal, &buf[6], sec_len); >>> + >>> + if (av_bswap16(crc) ^ crc_cal) { >>> + av_log(s->avctx, AV_LOG_ERROR, "CRC mismatch!\n"); >>> + if (s->err_recognition & AV_EF_EXPLODE) >>> + return AVERROR_INVALIDDATA; >>> + } >>> + } >>> + } >>> >> >> For files with crcs and with damage, do they sound better with the >> check and error out or without ? >> >> The behavior which provides the best user experience should be the >> default >> >> It also may make sense to add one of AV_EF_CAREFUL / AV_EF_COMPLIANT / >> AV_EF_AGGRESSIVE >> depending on how the check affects actual real world files >> > > This is just a quick check to verify the files are uncorrupted, it shouldn't > make broken files sound better unless the decoder somehow outputs white noise > when it tries to decode them. > I corrupted some files with -bsf:a noise=0.5 and couldn't notice an > improvement > with or without -err_detect crccheck+explode even though the outputs looked > different. crccheck+explode makes much less errors about incorrect timestamps. > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org <mailto:ffmpeg-devel@ffmpeg.org> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > <https://ffmpeg.org/mailman/listinfo/ffmpeg-devel> >
Ping? Could someone take a look at this patch and my other 2 (apedec and pngdec CRC)? _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
