Re: [FFmpeg-devel] [PATCH 2/4] avcodec/ffv1: Implementation of the CRC proposal for v4
On Fri, Oct 18, 2019 at 08:24:21PM +0200, Michael Niedermayer wrote: > On Fri, Oct 18, 2019 at 03:09:48AM +0200, Lynne wrote: > > Oct 17, 2019, 23:25 by mich...@niedermayer.cc: > > Signed-off-by: Michael Niedermayer > > --- > > libavcodec/ffv1.h| 1 + > > libavcodec/ffv1dec.c | 10 +++--- > > libavcodec/ffv1enc.c | 10 +++--- > > 3 files changed, 15 insertions(+), 6 deletions(-) > > > > Why 0x4964AF46 instead of 0x? > > CRC32 of 0x4964AF46 is 0x > > its effect is just to apply a 0x flip where its needed on the decoder > side > > This is the result of building a block [data] + [32bit checksum] which as a > whole has a CRC of 0. > So the code can be made simpler on the decoder side, the checksum no longer > represents a special case and if you want to apply error correction also > the checksum is not a special case > > If theres a more beautifull way to achive the same then iam certainly > interrested in that will apply all patches of this set except this. I intend to apply this one when the specification is updated thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Dictatorship: All citizens are under surveillance, all their steps and actions recorded, for the politicians to enforce control. Democracy: All politicians are under surveillance, all their steps and actions recorded, for the citizens to enforce control. signature.asc Description: PGP signature ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-devel] [PATCH 2/4] avcodec/ffv1: Implementation of the CRC proposal for v4
On Fri, Oct 18, 2019 at 03:09:48AM +0200, Lynne wrote: > Oct 17, 2019, 23:25 by mich...@niedermayer.cc: > Signed-off-by: Michael Niedermayer > --- > libavcodec/ffv1.h| 1 + > libavcodec/ffv1dec.c | 10 +++--- > libavcodec/ffv1enc.c | 10 +++--- > 3 files changed, 15 insertions(+), 6 deletions(-) > > Why 0x4964AF46 instead of 0x? CRC32 of 0x4964AF46 is 0x its effect is just to apply a 0x flip where its needed on the decoder side This is the result of building a block [data] + [32bit checksum] which as a whole has a CRC of 0. So the code can be made simpler on the decoder side, the checksum no longer represents a special case and if you want to apply error correction also the checksum is not a special case If theres a more beautifull way to achive the same then iam certainly interrested in that Thanks -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB "I am not trying to be anyone's saviour, I'm trying to think about the future and not be sad" - Elon Musk signature.asc Description: PGP signature ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-devel] [PATCH 2/4] avcodec/ffv1: Implementation of the CRC proposal for v4
Oct 17, 2019, 23:25 by mich...@niedermayer.cc: Signed-off-by: Michael Niedermayer --- libavcodec/ffv1.h| 1 + libavcodec/ffv1dec.c | 10 +++--- libavcodec/ffv1enc.c | 10 +++--- 3 files changed, 15 insertions(+), 6 deletions(-) Why 0x4964AF46 instead of 0x? ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
[FFmpeg-devel] [PATCH 2/4] avcodec/ffv1: Implementation of the CRC proposal for v4
Signed-off-by: Michael Niedermayer
---
libavcodec/ffv1.h| 1 +
libavcodec/ffv1dec.c | 10 +++---
libavcodec/ffv1enc.c | 10 +++---
3 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/libavcodec/ffv1.h b/libavcodec/ffv1.h
index f0bb19350a..3edf9dfca3 100644
--- a/libavcodec/ffv1.h
+++ b/libavcodec/ffv1.h
@@ -114,6 +114,7 @@ typedef struct FFV1Context {
int use32bit;
int ec;
+unsigned crc_flip;
int intra;
int slice_damaged;
int key_frame_ok;
diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
index 261e0cf70c..bc2b776754 100644
--- a/libavcodec/ffv1dec.c
+++ b/libavcodec/ffv1dec.c
@@ -500,8 +500,12 @@ static int read_extra_header(FFV1Context *f)
if (f->version > 2) {
unsigned v;
-v = av_crc(av_crc_get_table(AV_CRC_32_IEEE), 0,
- f->avctx->extradata, f->avctx->extradata_size);
+
+if (f->version > 4 || (f->version == 4 && f->micro_version >= 3))
+f->crc_flip = 0x;
+
+v = av_crc(av_crc_get_table(AV_CRC_32_IEEE), f->crc_flip,
+ f->avctx->extradata, f->avctx->extradata_size) ^
f->crc_flip;
if (v || f->avctx->extradata_size < 4) {
av_log(f->avctx, AV_LOG_ERROR, "CRC mismatch %X!\n", v);
return AVERROR_INVALIDDATA;
@@ -903,7 +907,7 @@ static int decode_frame(AVCodecContext *avctx, void *data,
int *got_frame, AVPac
buf_p -= v;
if (f->ec) {
-unsigned crc = av_crc(av_crc_get_table(AV_CRC_32_IEEE), 0, buf_p,
v);
+unsigned crc = av_crc(av_crc_get_table(AV_CRC_32_IEEE),
f->crc_flip, buf_p, v) ^ f->crc_flip;
if (crc) {
int64_t ts = avpkt->pts != AV_NOPTS_VALUE ? avpkt->pts :
avpkt->dts;
av_log(f->avctx, AV_LOG_ERROR, "CRC mismatch %X!", crc);
diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c
index c521b7d445..4beb8fde35 100644
--- a/libavcodec/ffv1enc.c
+++ b/libavcodec/ffv1enc.c
@@ -417,7 +417,7 @@ static int write_extradata(FFV1Context *f)
if (f->version == 3) {
f->micro_version = 4;
} else if (f->version == 4)
-f->micro_version = 2;
+f->micro_version = 3;
put_symbol(c, state, f->micro_version, 0);
}
@@ -459,7 +459,7 @@ static int write_extradata(FFV1Context *f)
}
f->avctx->extradata_size = ff_rac_terminate(c, 0);
-v = av_crc(av_crc_get_table(AV_CRC_32_IEEE), 0, f->avctx->extradata,
f->avctx->extradata_size);
+v = av_crc(av_crc_get_table(AV_CRC_32_IEEE), f->crc_flip,
f->avctx->extradata, f->avctx->extradata_size) ^ (f->crc_flip & 0x4964AF46);
AV_WL32(f->avctx->extradata + f->avctx->extradata_size, v);
f->avctx->extradata_size += 4;
@@ -898,6 +898,10 @@ FF_ENABLE_DEPRECATION_WARNINGS
avctx->slices);
return AVERROR(ENOSYS);
slices_ok:
+
+if (s->version > 3)
+s->crc_flip = 0x;
+
if ((ret = write_extradata(s)) < 0)
return ret;
}
@@ -1254,7 +1258,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
if (f->ec) {
unsigned v;
buf_p[bytes++] = 0;
-v = av_crc(av_crc_get_table(AV_CRC_32_IEEE), 0, buf_p, bytes);
+v = av_crc(av_crc_get_table(AV_CRC_32_IEEE), f->crc_flip, buf_p,
bytes) ^ (f->crc_flip & 0x4964AF46);
AV_WL32(buf_p + bytes, v);
bytes += 4;
}
--
2.23.0
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