[XviD-devel] discussion continue...

[Marc FD]

----- Message d'origine -----
De : "skal" <skal@planet-d.net>
À : <xvid-devel@xvid.org>
Cc : <XviD-devel@xvid.org>
Envoyé : mardi 10 septembre 2002 13:52
Objet : Re: [XviD-devel] discussion continue...


> Marc,
>
> On Mon, 2002-09-09 at 17:24, Marc FD wrote:
>
> > regarding "Hadamarad ;-)" my stuff was in fact 25% slower than skal's.
> > I'm not that bad if i can reach a master in the matter ;))
>
> you can do much better than this, by cooperating:
>
> take the first_pass+transpose code, throw it away,
> and replace it by a mix of yours and monsti's (list not
> exhaustive). Keep the second pass as is, anyhow.
> It's a 5min work, and the result will eventually be
> better by, let's say 20% at least, than *any* of the
> original codes, no matter what tremendous brain juice
> is injected hand-optimizing them *separately*.
> Perfect example of code cooperation.
>
> here are the details:
>
> the O(N.lnN) algo ("butterfly") beats your O(N^2) one.
> Take it for granted. If not for N=8, it'll be for N=16,
> or higher...
> But, we're not running any N, but specifically N=8.
> Each butterfly pass takes 58cycles, but needs 2 transposes
> (O(N)), which, for N=8, takes ~80cycles. Hence the
> total: 2*58c + 80c = 196c. But if we get rid
> of the transpose+1butterfly and replace it by your
> O(N^2) code, we gain: 80c+58c - 112c = 26c. Easy money
> in 5minutes (the time it takes to write an angry mail ;).
>
> bye,
>
> Skal

sorry, maybe i'm sumb, (i'm even pretty sure of that!)
but i understand almost nothing of what you said :
what is O ? InN ? why N^2

i used full butterflyed vertical (2x32) and horizontal(8x8).
i thinked it was slower because i'm not using
only vertical + transpose (faster?)

but i like the idea of cooperating ;)

@gruel

SKIP detection based on WHT don't work better.
I'm always facing this damn smearing...
I'll continue my investigations....
very hard to find a _so_ good detection than it _even_ detects clouds moving
!

BTW, could you answer my e-mail ;) (regarding the Histogramm-stuff i need to
begin)
Thx.