Yes exactly, I was really excited when I found out that you do not need a FFT to do speech processing.
If you look at the code of (phone/voice) codecs GSM/Speex/Opus you can see that you can estimate the spectral envelope (or the configuration of a physical tube model for the vocal tract) in time domain with linear prediction coefficients (LPC).
And it is simple, e.g. the often used Levinson-Durbin algorithm is just 22 lines of C code. It is an interesting exercise to build your own vocoder from scratch that fits in a single screen page.
Many of the code snippets I have seen (which likely have already processed your voice) are just translations of the Fortran code of the book "Linear Prediction of Speech" by Markel and Gray (1976).
Re:The vocal effects of Daft Punk
by nonrandomstring on Monday May 05, 2025 @02:12PM
(#43897801)
Ah yes, ladder or lattice filters. If you don't mind old fashioned
mailing lists there's still a few of hanging around in
[email protected] where code gets shared.
Re:The vocal effects of Daft Punk
by nonrandomstring on Monday May 05, 2025 @09:19AM
(#43894833)
I thought it was phase synchronous overlap add, but I just checked and
now I'm not so sure.
Has anyone got more details?
Re:The vocal effects of Daft Punk
by marcedwards on Monday May 05, 2025 @09:24AM
(#43894873)
That gives me something to research! I’ve only scratched the surface of IVL’s algorithm, but intend to look into it further.
Oh, it also might be of interest that the IVL algorithm isn’t FFT-based. I think their harmonizers sound better than the rest, so maybe FFT isn’t the best way to go.