Apr 7, 2019, 12:56 AM by mich...@niedermayer.cc:
> On Sat, Apr 06, 2019 at 10:44:00AM +0200, Lynne wrote:
>
>> Apr 4, 2019, 10:30 AM by >> mich...@niedermayer.cc
>> <mailto:mich...@niedermayer.cc>>> :
>>
>> > On Wed, Mar 06, 2019 at 02:47:37PM +0100, Lynne wrote:
>> >
>> >> 6 Mar 2019, 11:22 by >> >> d...@lynne.ee <mailto:d...@lynne.ee>>>
>> >> <mailto:>> d...@lynne.ee <mailto:d...@lynne.ee>>> >>> :
>> >>
>> >> > The CRC flag is only signalled once every few minutes but CRC is still
>> >> > always present so the patch uses the file version instead.
>> >> > CRC on 24-bit files wants non-padded samples so skip such files.
>> >> > Some corrupt samples may have been output before the final check
>> >> > depending on the -max_samples setting.
>> >> >
>> >> v2 attached
>> >>
>> >> apedec.c | 26 +++++++++++++++++++++++++-
>> >> 1 file changed, 25 insertions(+), 1 deletion(-)
>> >> c0cc550d77927ee0349094a4976f73d0ef671ff6
>> >> 0001-apedec-add-ability-to-check-CRC-v2.patch
>> >> From 68c25bb026761eacda3c276148e2beb34e8929fd 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 11:01:01 +0000
>> >> Subject: [PATCH v2] apedec: add ability to check CRC
>> >>
>> >> The CRC flag is only signalled once every few minutes but CRC is still
>> >> always present so the patch uses the file version instead.
>> >> CRC on 24-bit files wants non-padded samples so skip such files.
>> >> Some corrupt samples may have been output before the final check
>> >> depending on the -max_samples setting.
>> >> ---
>> >> libavcodec/apedec.c | 26 +++++++++++++++++++++++++-
>> >> 1 file changed, 25 insertions(+), 1 deletion(-)
>> >>
>> >> diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c
>> >> index 15eb416ba4..a20d884606 100644
>> >> --- a/libavcodec/apedec.c
>> >> +++ b/libavcodec/apedec.c
>> >> @@ -24,6 +24,7 @@
>> >>
>> >> #include "libavutil/avassert.h"
>> >> #include "libavutil/channel_layout.h"
>> >> +#include "libavutil/crc.h"
>> >> #include "libavutil/opt.h"
>> >> #include "lossless_audiodsp.h"
>> >> #include "avcodec.h"
>> >> @@ -147,7 +148,8 @@ typedef struct APEContext {
>> >> int fset; ///< which filter set to use
>> >> (calculated from compression level)
>> >> int flags; ///< global decoder flags
>> >>
>> >> - uint32_t CRC; ///< frame CRC
>> >> + uint32_t CRC; ///< signalled frame CRC
>> >> + uint32_t CRC_state; ///< accumulated CRC
>> >> int frameflags; ///< frame flags
>> >> APEPredictor predictor; ///< predictor used for final
>> >> reconstruction
>> >>
>> >> @@ -730,6 +732,7 @@ static int init_entropy_decoder(APEContext *ctx)
>> >>
>> >> /* Read the frame flags if they exist */
>> >> ctx->frameflags = 0;
>> >> + ctx->CRC_state = UINT32_MAX;
>> >> if ((ctx->fileversion > 3820) && (ctx->CRC & 0x80000000)) {
>> >> ctx->CRC &= ~0x80000000;
>> >>
>> >> @@ -1548,6 +1551,27 @@ static int ape_decode_frame(AVCodecContext *avctx,
>> >> void *data,
>> >>
>> >> s->samples -= blockstodecode;
>> >>
>> >> + if ((avctx->err_recognition & AV_EF_CRCCHECK) &&
>> >>
>> >> + (s->fileversion >= 3900) && (s->bps < 24)) {
>> >>
>> >
>> > what about file versions other than this ? do they have no crc ?
>> >
>> They have a different CRC version which is poorly documented.
>>
>>
>> >
>> > what about othet bps ?
>> >
>> 24 bit CRC needs to ignore the zeroes padding each sample in 32 bits. I
>> couldn't find any 24-bit files so I left that for a future patch.
>>
>
> can such a file not be generated ? or
> maybe printing a note and asking for a sample in this case would be an option
> if noone has one either ...
>
I think skipping the check for such files is okay for now. Its just for
verification purposes after all, and not all decoders implement the option but
silently skip it.
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