Re: [FFmpeg-devel] [PATCH] avcodec/mpegvideo: Remove spec-incompliant inverse quantisation

From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] avcodec/mpegvideo: Remove spec-incompliant inverse quantisation
Date: Thu, 9 Nov 2023 23:16:39 +0100
Message-ID: <20231109221639.GH3543730@pb2> (raw)
In-Reply-To: <15041633.235GFhGzie@basile.remlab.net>

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On Thu, Nov 09, 2023 at 10:52:19PM +0200, Rémi Denis-Courmont wrote:
> Le torstaina 9. marraskuuta 2023, 22.45.35 EET Alexander Strasser a écrit :
> > I can't see how the reason for the presence of code can be ultimately
> > defined objectively and non-arbitrary.
> 
> Ultimately, this was discussed and decided in a meeting, which Michael 
> attended (albeit remotely) and for which meeting notes were published.

maybe i misremember as i was a bit sick that day
but there are 2 pieces of code
there was the "fast mode code" that i thought was discussed this is
disabled by default and we aggreed to remove it

the change here is about the default code path so this is very different
it will affect users with default options.

I do not remember this was discussed but its quite possible people
had a different interpretation what the words meant that where said.

This definitly should be tested before its applied. Whoever the burden falls
on is not my argument but ATM i have many things to do so i will not be able
to test this in the next days

> 
> That being the case, I don't see why Andreas should have to perform extensive 
> testing and write extensive justification. He could have done and that would 
> have been nice, but that is all.

I never meant that there should be extensive testing
but teh removal of a optimization from the default codepath should be
tested.
Also about spec non compliance, if this was so bad, being in the default
path there would be bug reports so iam a bit sceptic. not saying it
shouldnt be removed just saying we should look before removing it

thx

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

I have often repented speaking, but never of holding my tongue.
-- Xenocrates

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