[x264-devel] Re: [PATCH] Altivec optimizations for quant4x4, quant4x4dc, quant8x8, sub8x8_dct8, sub16x16_dct8, pixel_sa8d_8x8, pixel_sa8d_16x16, *idct8*

[Loren Merritt]

On Mon, 2 Oct 2006, Guillaume POIRIER wrote:
> On 10/2/06, Loren Merritt <lorenm at u.washington.edu> wrote:
>
>> The application I have in mind that needs unaligned sa8d is: predict
>> whether the current macroblock will use 8x8 vs 4x4 dct, and if the guess
>> is 8x8 then use sa8d instead of satd in motion estimation.
>
> Ok. In other words, current implementation of sa8d _happens_ to be fed
> with simple alignment and strides, but you plan to add/modify the
> motion estimation pass in which sa8d won't be blessed with these
> simple alignments/strides, right?
> (yes, I'm trying to repeat what you said with my own words to make
> sure I understood correctly).

Strides will stay simple, but yes.

> By any chance, do you know the options that I should pass to x264 that
> would allow me to test all strides and alignments in a real world
> encode? (activating all options being both overkill and slow).

"-b1 -Aall -8" should be enough.

> I've got another question: if ever the computation returned by either
> one of SAD, SATD, SA8D is incorrect, that doesn't mean that the
> resulting picture will be corrupted, right? This would just lead to
> incorrect motion estimation and therefore sub-optimal compression,
> right?

right.

--Loren Merritt

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