May 22, 2020, 23:42 by d...@lynne.ee:
> Posting this again.
>
> 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.
>
> Patch attached.
>
Patch actually attached.
>From 68766a5b125d20b58fd343e848582af3cad31ab7 Mon Sep 17 00:00:00 2001
From: Lynne <d...@lynne.ee>
Date: Wed, 6 Mar 2019 11:01:01 +0000
Subject: [PATCH 1/3] 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 2d1925018e..a2d985063c 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
@@ -750,6 +752,7 @@ 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;
@@ -1577,6 +1580,27 @@ 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)) {
+ uint32_t crc = s->CRC_state;
+ const AVCRC *crc_tab = av_crc_get_table(AV_CRC_32_IEEE_LE);
+ for (i = 0; i < blockstodecode; i++) {
+ for (ch = 0; ch < s->channels; ch++) {
+ uint8_t *smp = frame->data[ch] + (i*(s->bps >> 3));
+ crc = av_crc(crc_tab, crc, smp, s->bps >> 3);
+ }
+ }
+
+ if (!s->samples && ((~crc >> 1) ^ s->CRC)) {
+ av_log(avctx, AV_LOG_ERROR, "CRC mismatch! Previously decoded "
+ "frames may have been affected as well.\n");
+ if (avctx->err_recognition & AV_EF_EXPLODE)
+ return AVERROR_INVALIDDATA;
+ }
+
+ s->CRC_state = crc;
+ }
+
*got_frame_ptr = 1;
return !s->samples ? avpkt->size : 0;
--
2.27.0.rc0
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