Vocoder Idea

[Christian Hofmann]

On Fri, 5 Jun 1998 09:50:34 +0200 (MET DST)
Martin Czech <martin.czech at intermetall.de> wrote:

> I have the impression that this channel saving trick won't work.
> The analysis filter needs some time to measure the incomming
> spectrum correctly, and this time is inverse proportional to the
> filter frequency (Fourier Theory). This would mean that the filter
> has to stay very long at the lowest frequencys in order to run in,
> so the overall analysis response will be very slow.
> Say fmin=40Hz ->Tcycle = 25ms, if we need 3 cycles to run in this makes
> 75 ms just for the lowest channel. Adding time for the other channels
> will lead to s&h update intervals of > 0.2s, this seems
> to me as a very slow response of the overall system.

That is, if you're trying to emulate normal vocoder operation.

But the idea of inserting S&Hs into the channels' VCA control signals
may produce some interesting FX (well, I guess it won't improve speech
quality :-)   Has anyone tried something like that?

BTW, what about completely _synthesizing_ the control signals, e.g. using
a shepard generator and thoroughly mixing up the channel numbers...? Or
multiple random voltages in the LFO freq range (as used in the good old
Elektor Formant).

cu
Christian