Analog Filters -> Digital

[Sean Costello]

Brian Towles wrote:

> as for ffts: i think you could run into problems related to the delay
> assocaited with gathering the data points for an FFT, not actually doing the
> computation.  for example, it might take 5ms of samples to detect the low-end
> of frequencies you would be interested in for vocoding ( in the 100Hz range ) -
> this limits the speed of update for all the filters. one solution to this
> problem is to use overlapped fft windows, but then computation speed starts
> becoming an issue.  these problems occur in the modulation analysis.  the
> delays caused by the fft-ifft pair for the output would be even worse.

5ms isn't all that much.  You could probably tolerate up to 20-30 ms of
output delay without it becoming too much of a problem, as long as the
undelayed input isn't mixed with the output.  Most "real-time" computer
music programs will have such a delay (around 36 milliseconds
input-output lag for MSP, which is one of the best).  Not saying it is a
good thing, but the way most operating systems works makes it difficult
to avoid such a lag, apparently.

Sean Costello