Lou Bunk

Hi, I am digging into the FFT capabilities of MSP and am working on a subpath for pfft~ that can do multiple types of FFT analysis and processing; basically I am doing the ones in the FFT tutorial like noisegate, convolution, crossover filter, etc. I built individual pfft subpathces for each and am now wanting to put them all in one subpatch and have a umenu (or some other method) for chosing which process is active or even chaining multiple process (in various orders) while still within the pfft subpatch, that is still as FFT data. I have done this successfully with convolution and noisegate.

My question is: is there any advantage in doing it this way as opposed to just having multiple pfft objects each with its own subpatch that does one of the above fft process. It seems with multiple pfft objects in a chain, the multiple analysis and re-synthesis in and out of fft would create a different (perhaps uglier?) sound then doing all the processing without resynthesizing between each process. It seems one pfft subpatch would also use less cpu.

There are also more questions concerning real and imaginary numbers which I am just guessing at...

fft-choose-among-multi-processes-in-same-pfft-subpatch

Yes, the direct advantage is that you do the conversion time domain-> spectral -> time (FFT) only once. With two [pfft~] objects, you use twice the processing power.

There might be a difference in the sound as well (adding conversions can certainly not improve the sound quality!)

Hi Lou,
Yes, the direct advantage is that you do the conversion time domain-> spectral -> time (FFT) only once. With two [pfft~] objects, you use twice the processing power.

So, you are doing the right thing!
See you,
Jean-François.


By the way, conversion between cartesian and polar representation of imaginary numbers is expensive. Depending on what kind of process you have, you might save on that as well by embedding everything in a unique [pfft~]. For instance, if you do processes in series, you might do all the processes that work directly on imaginary numbers in a row, then all processes that need polar representation is a row as well.

FFT choose among multi processes in same pfft subpatch