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> > 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 thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB There will always be a question for which you do not know the correct answer.
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