Re: [FFmpeg-devel] [PATCH] avcodec/ffv1: Store slices*planes with the minimum bits needed after remap

From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] avcodec/ffv1: Store slices*planes with the minimum bits needed after remap
Date: Thu, 3 Apr 2025 02:07:36 +0200
Message-ID: <20250403000736.GM4991@pb2> (raw)
In-Reply-To: <72c55c0a-3bb2-44dc-a646-663421c20630@mediaarea.net>

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Hi Jerome

On Wed, Apr 02, 2025 at 11:31:53PM +0200, Jerome Martinez wrote:
> Le 02/04/2025 à 23:13, Michael Niedermayer a écrit :
> > [...]
> > 
> > This improves compression as wrap around can be cheaper to reach a
> > value.
> 
> 
> There is an issue in FFV1 version <=3 with RCT, bit depth of resulting
> luminance plane was 1 more than needed (RCT adds 1 bit to chrominance but
> not to luminance, but with current spec all planes have 1 additional bit),
> preventing in practice the wrap around for luminance, do I understand well
> that the remap would mitigate such issue?

yes, in fact with version 4 that issue is fixed with this patch without remap too

and its not just the luminance plane, its alpha too

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable

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