[x264-devel] Question about ME in x264

[Jason Garrett-Glaser]

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).

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