[FFmpeg-devel] [PATCH 2/4] avcodec/ffv1: Implementation of the CRC proposal for v4

[Michael Niedermayer]

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

[...]

-- 
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.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20191109/20cd88ce/attachment.sig>