[PD] Gem and audio, multiprocessors, Mac

Jean-Marie Adrien jma at jeanmarie-adrien.net
Wed Dec 7 11:52:00 CET 2011

Hi list,

Is there a strategy to optimize GEM video processing and real time  
audio on a single Mac using pd~  :

Audio in subprocess or in main process ?
Any startup flags ? chmod +s stuff ? shm settings ?
Run two instances of PD with messages between them ?
Subprocess fifo size ?

The idea would be to give a priority to sound versus video, if  
absolutely necessary.

Situation :

On a single Mac (pro or mini), Gem (pix_video &  tracking, ordinary  
resolution and fps) and real time audio (10 channels, mainly reading  
from disk), dispatched on four processor cores via pd~. The sound is  
generated in the subprocess (big latency 512), the video in the main  
patch. pd-extended 42.5 osX 10.7 &10.6, gem 93, 92.

Problem :

Sound is distorted when Gem is rendering, and becomes immediatly  
perfect when stopping rendering (destroying the gem window).
Processors seem ok (each core at 75%).

Sticking with this problem for a couple of months,
Looked around in archives but didn't find any clear element.


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