[MPlayer-dev-eng] [PATCH] (new version) AltiVec: dct64 for mp3lib, IMDCT for liba52, detection code

[Daniel Egger]

On Sun, 2003-01-19 at 15:23, Romain Dolbeau wrote:

> The guys who did the IDCT did an incredible job, the AltiVec
> version is _much_ faster than simple_idct. Thanks, folks :-)

Jepp, I also used the libmpeg2 version; it's a tad bit slower than
the motorola one but has a much better precision. I also wrote my own
version but this one is really bad in performance terms....

> This code alone takes 32% of your computation, so
> the code would take 28% less time to run with
> the AltiVec IDCT, and the IDCT would take about
> 5.55% of the total execution time. At that point,
> synth_1to1 and dct64_1 seem to take a lot of time :-)

Oh yes, but it's still beaten a lot by the MC functions.
Especially when having the altivec idct in place the granularity
of the profile improves a lot and one can see the memory bottlenecks.

As I said; I had the MC working a year ago but it broke badly due to
misalignment which was introduced later. I tried to compensate by
two different methods: Generally aligning all read data - this really
blew performance, and special casing - this really introduced some 
nasty bugs and bloated code...

I don't see any light here before we some reasonable alignment (at least
64bit) back or do some nasty surgery on the interfaces. Needless to say
I really lack time, if you're interested in looking at some of the 
incorrect or old code I'd be glad to send it over....

-- 
Servus,
       Daniel
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