[FFmpeg-devel] [PATCH 2/4] avcodec/ffv1: Implementation of the CRC proposal for v4
Michael Niedermayer
michael at niedermayer.cc
Sat Nov 9 17:06:09 EET 2019
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 michael at niedermayer.cc:
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> > libavcodec/ffv1.h | 1 +
> > libavcodec/ffv1dec.c | 10 +++++++---
> > libavcodec/ffv1enc.c | 10 +++++++---
> > 3 files changed, 15 insertions(+), 6 deletions(-)
> >
> > Why 0x4964AF46 instead of 0xFFFFFFFF?
>
> CRC32 of 0x4964AF46 is 0xFFFFFFFF
>
> its effect is just to apply a 0xFFFFFFFF 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
[...]
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Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
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