Re: [FFmpeg-devel] [PATCH] avcodec/ffv1: Implement 2D RLE for remap

[Michael Niedermayer <michael@niedermayer.cc>]

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Hi Jerome

On Sat, Mar 22, 2025 at 06:54:25PM +0100, Jerome Martinez wrote:
> Le 22/03/2025 à 18:45, Michael Niedermayer a écrit :
> > [...]
> > Also I failed to find any worthy gain from adjusting mul_count so
> > while the code in the encoder looks complex ATM alot of that can be
> > dropped later if for example we choose to never put mul_count > 1 into
> > the specification and ATM it makes no sense to put that in as theres no
> > significant gain with the material i tested
> 
> I would prefer we don't put mul_count > 1 related code in FFmpeg, even if it
> is still experimental, without a use case demonstrating that this is useful.

Ok, ive done some more tests

mul_count>1 is for fixed point in float and decimal mantisse*exponent
formats. This is also what the paper concentrated on that ive looked at.

Real world sensors return integers (to the best of my knowledge), so these
fixed point in float cases are expected to be significant.

Sadly i have very little of any float32 material. So to test this i
had to generate my own. using the same tonemap and source from last time
i put a gbrp16 in the middle to make it 16bit fixed point in float.

and then encode this with a single static repeated dumb handwritten
mul_count=512 table vs the computer optimized mul_count=1 table optimized
for each slice. Still the mul_count=512 tables are 6% smaller overall

I see the same effect with a random gbrp10 image in float32, just that
the tables are all smaller.

I thus will move forward with commiting the code i have
I also have simplified the code more today.

Droping all mul_count > 1 code would require an alternative solution.

thx

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

Modern terrorism, a quick summary: Need oil, start war with country that
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people, be surprised about them taking revenge and drop even more bombs
and strip your own citizens of their rights and freedoms. to be continued

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