[PD] Gem -0.87 Performance Tuning (disk IO)

bbogart at ryerson.ca bbogart at ryerson.ca
Sat Dec 7 06:47:05 CET 2002

Hello All,

I'm working on the implimentation of my thesis
project in pd/Gem and have run into some performance
issues (in linux using -rt).

I have 4 video clips (Photo JPEG 256x256 quicktimes
from 3000-11000 frames) and about 800 128x512 jpeg

any two of the 4 video clips are playing at any one
time, and being mixed using alpha.
Three of the jpegs are being used at any one time.
The jpegs are chosen by the output of some chaos math. 

The video stuff playes great on its own, and the
stills come up great too, animation is smooth and
nice (Geforce2 MX-400) 

The problem is that when I load a new set of jpegs
the video playback freezes for about 500ms and then
continues. It looks like its the disk access causing
the issue, since the videos are being played off
disk. I tried putting the videos on a different HD
than the images, but there is still that pause. 

Anyone have any suggestions on what I could do to
improve the performance? This is an installation and
as such needs to run for days on end without a
performance drop. 

In my tests using the images without the video I
could open a new jpeg every 80ms or so, very
impressive. But why the video render pause? I
thought about using pix_multiimage, but 800 128x512
tiffs is probably too much for my 640MB of RAM.

Any suggestions would be appreciated. 


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