[PD] Pd and gpgpu

marius schebella marius.schebella at gmail.com
Sat Nov 10 13:47:52 CET 2007

no, I don't know how to use glsl for audio. I thought you were talking 
about graphical things. for audio you somehow would have to copy a 
buffer of audio data to the graphicscard (I don't know an object that 
could do that, but maybe there is one?...), then do your computations 
and then read it back into ram and then pass it to the soundcard.
I also don't see, how you would time and synchronize your graphics card 
with the soundcard.
it is true that the gpu is unused most of the time and could be used to 
do fast calculations, but the main output for graphicscards is the 
screen and reading back into ram can be slow. (of course "slow" is a 
relative term). I also see a problem in the different formats for audio 
and images. most graphics cards are optimized for vec4 processings (4 
parallel color channels). and audio...
OTOH I know that max/msp has some shaders that do audio computation. You 
could have a look at that and then maybe know how to do it in pd, too.
although I think that is all related to jitter functionality, and pd 
can't really do that.

Julian Villegas wrote:
> Thank you Marius,
> Do I need to use GEM? I'm not doing anything with video, or graphics, I'm working only with audio. What I'd like to do in a first stage is to send to the GPU a set of data (harmonic peaks from live signals) and do some calculations there, then read back that into the program and proceed according to the results. In a second stage, the FFT and the spectral analyis could be performed there too. Chris mentioned that latency might be an issue since reading data from the GPU is slow, I don't know much about it but I think it shouldn't be since many cards can (and in fact must) use the main memory, so reading from memory should be as fast as it is when I read it with the CPU.
> Also, I'm working in Mac OS 10.5, using Miller's version of Pd. Have you have any problems with Leopard and your patches? 
> Thank you again, and I'll read the patches you post to see if I can get more ideas from them...
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