Analog Filters -> Digital

[Thomas Hudson]

You may want to post this to the music-dsp mailing list:

http://shoko.calarts.edu/~glmrboy/musicdsp/music-dsp.html

Lot's of discussion on subjects like this.

Thomas

Brian Patrick Towles wrote:
> 
> sorry, if this is a little off topic.
> 
> for a class design project, i've tricked my group into programming a
> software vocoder :)  we're going to implement the filterbanks as discrete
> bandpass filters - the same way analog vocoders work.  however, none of
> the group members knows a good approach to designing these digital
> filters.  optimally, we would have a procedure for turning s-domain (
> continuous ) filters into z-domain ( discrete ) filters - just because i'm
> fairly confident i could design the filterbank using analog filters.
> 
> i've read a little about the bilinear-transform, which seems to do
> continuous to discrete transformation, but i don't know if that's what we
> are looking for ... does anyone have any ideas or algorithms for
> converting analog filters into their digital counterparts?
> 
> also, before anyone yells "just use fft's", we're aiming for real-time.
> i'm fairly convinced that fft's have too much associated delay to work in
> this application.  we want real fast, smooth spectral analysis of the
> input signal for the optimal vocoding effect.
> 
> thanks,
> 
> brian
> 
> aside: we did an initial presentation of the vocoder, but only mentioned
> it's voice compression applications ... hopefully, we'll shock the class
> and professor with our final presenation and a chorus of robot voices :)