[x265] [PATCH Review only] asm: added psy_acEnergy_pp_4x4 in sse4 for psyCost_pp

[Deepthi Nandakumar]

Psy-energy is not always measured at the CU level. estIntraPredQT makes RD
decisions at the PU level (search.cpp: 1532). Also, chroma uses the psy-rd
4x4 cost loop for 8x8 CUs.

I see the concern though about performance reduction due to an in-loop if
(size) check. There's no neat way around this, though.

On Wed, Dec 17, 2014 at 12:33 PM, Steve Borho <steve at borho.org> wrote:
>
> On 12/17, Divya Manivannan wrote:
> > The encoder uses 4x4 block size by testing with these two videos
> > NebutaFestival_2560x1600_60_10bit_crop.yuv and 720p50_parkrun_ter.y4m.
> > Since there is no similar function definition, I have generated the new
> > function definition for 4x4.
>
> It can encode intra 4x4, but the CU in that case is still 8x8 and
> psy-energy is always measured at the CU level (for pixels, for residual
> it might measure 4x4 shorts).
>
> But why make a function that can only measure one half of the psy-value
> when there already exists a function prototype for generating the full
> energy score?
>
> I can guess where this is headed, where you write one function that
> fills in an array of costs and then call it twice and have the C code
> sum the abs(diff) of those costs, but if this is the direction you are
> headed then the function prototype needs to be the same for all block
> sizes.  Adding conditional paths for different block sizes will make the
> function slower, in whole, as will requiring two function calls to make
> one energy measurement.
>
> --
> Steve Borho
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