[x264-devel] Question about ME in x264

[kenter]

Thanks for your reply, I also want to ask more about this issue, I worked on
transplant ME into GPU, the cost of GPU memory can be ignored and
super-sampling can also moved to GPU. so, It seems the penalty of
pre-calculate is trivial.

However, when call h->mc.get_ref each time, the different branch in get_ref
function will lead to decrease the degree of parallelism, under this
circumstance, Is it benefit if pre-calculate of Qpel?


2009/7/15 Jason Garrett-Glaser <darkshikari at gmail.com>

>  On Tue, Jul 14, 2009 at 11:49 PM, kenter<kenter83 at gmail.com> wrote:
> > Hi, All
> >     I currently study about the ME of x264, I noticed when perform 1/4
> and
> > 1/2 pel search, we need to call function h->mc.get_ref first,  which used
> to
> > getthe aveage value of two pixel when needed.
> >     I'm puzzeled that why not pre-calculate of 1/4 and 1/2 pel in the
> very
> > beginning of ME for the whole frame, so that when each time of spel ME,
> we
> > can directly get from buffer which can save the computation power of cpu?
>
> Halfpel is already precalculated; get_ref handles the interpolation
> from hpel samples.
>
> Qpel is pointless to precalculate as the memory cost is gargantuan (4x
> that of hpel) and provides no real benefit (qpel interpolation is
> trivial, while the extra cache cost is not).
>
> Dark Shikari
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