[FFmpeg-devel] a64 encoder

[Jason Garrett-Glaser]

On Sat, Jan 17, 2009 at 11:21 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sat, Jan 17, 2009 at 04:52:00PM +0100, Bitbreaker/METALVOTZE wrote:
>>
>> > reducing the colors before seems quite suboptimal, id rather convert each
>> > fullcolor "char" with dithering to what is available afterwards or even
>> > during the elbg code.
>> >
>> I have tried converting to a charset beforehand already some time ago,
>> it can lead to other problems therefore, depending on what area i
>> calculate the error. If i do a pixelwise compare, i gotta stick to the
>> ditherpatterns or error goes up.
>
> you shouldnt be comparing pixel wise, because if a minimal per pixel
> difference where the goal dither would always be inferrior to taking the
> closest color ...
> A likely better comparission is in 2d dct domain, with the low frequency
> coefficients more strongly weightet. But maybe some psychovissual
> comparission (x264 has some code for this ...)

Are these charsets 8x8?  In this case, here's one method that can be
done with existing ffmpeg code that is a bit similar to what x264
does:

define complexity( block ) = hadamard8_intra8x8

score (lower is better) = bit cost * lambda^2 +
abs(complexity(src)-complexity(dest)) * lambda + ssd(src,dest)

for some lambda.

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