[PD] PDP: better optimization for OSX?

cgc at humboldtblvd.com cgc at humboldtblvd.com
Thu Mar 4 18:31:13 CET 2004

Quoting derek holzer <derek at x-i.net>:

> Just playing around this week with PDP on a fairly new TiBook and have
> noticed it is horribly inefficient. A patch which runs between 50 and 
> 80% on my Gentoo 1.6 GHz laptop peaks out between 250 and 300% on the G4
> 1 GHz Mac! I can forward the patch to the list, but it is a simple video 
> mixer with the capability to loop sequences of 1-50 frames in a somewhat
> random order. Really only two [pdp_qt] objects going to a [pdp_mixer2]
> and a few [metro]s and [random]s to play the clips. Nothing special.

What sizes are the video clips?  That G4 will do two DV clips without any
problem given decent code.

I seem to recall that pdp uses the linux quicktime lib which, to be perfectly
blunt, is really terrible code.  If you switch to Apple's QT you will notice a
pretty large performance gain as the code has been fairly well tuned for PPC. 
For DV I think the difference in speed was something like 6 or 8 to 1 in favor
of Apple's QT last time I tested it.

Also, the standard pdp-qt object is RGB correct?  That's not such a good thing
for video and I'd be willing to bet that lots of time is spent in YUV->RGB

The processing objects in pdp don't have any Altivec, which is really an
absolute necessity for video.  Not using the vector unit is leaving most of the
CPU's potential unused. 

> We are using Yves' packages. I wonder if it is possible to optimize the
> Makefile better for the G4 processor?

You won't get a big enough performance boost from adding flags unless your
current build has optimization turned completely off.  You can try these on GCC 3.3:

-O3 -mtune-7450 -mcpu=7450 -falign-loops=16 -funroll-all 

Those are off the top of my head and the architecture stuff is automatically set
to the box you compile on (i.e. redundant) and the loop alignment and unrolling
doesn't really get you much unless the code is already setup to take advantage
of them.  It's worth a shot, but unless your are using a really screwed up
version of pdp right now it won't give huge benefits. 

> Any ideas?

Is GEM an option?  You won't be watching any video slideshows on that Tibook
using it.


> D.
> -- 
> derek holzer ::: http://www.umatic.nl
> ---Oblique Strategy # 203:
> "When is it for?
> Who is it for?"

I was always partial to 'Go slowly all the way around the outside' and 'Would
anybody want it?'

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