Demonstration Spectral Plugins for Windows (Pentium Pro or better).

This zipfile contains three example VST effects plugins using the phase vocoder.  The files should be 
copied into the VST Plugins folder(s) of your VST host application(s). They are all strictly mono
 only, so in Cubase VST, for example, they will have to be used as channel Inserts. 
They have only been tested  so far at the 44100 sample rate. On a Pentium II 333MHz machine 
each plugin runs cleanly in real time, running around 40% to 50% CPU load. Faster machines  can expect to
 run two or more simultaneously. There is no GUI - they use the default GUI provided by the host application.

They are based on programs from the CDP system (http://www.bath.ac.uk/~masjpf/CDP/CDP.htm), developed
by Trevor Wishart.

PVACCU:  spectral accumulation.  Applies feedback echo to each analysis channel, with the possibility
also to apply a pitch glissando up or down. Echo is amplitude dependent, so this effect is most apparent
when applied to percussive sounds, or any sound with distinct changes.

PVEXAG: exaggerates the spectrum. Positive exaggeration will emphasize spectral peaks, eventually 
becoming disinct pitches. Negative exaggeration flattens peaks, and larger values will effectively generate
 a granular noise. This can sometimes be effective for some percussive sounds, such as drum loops.

PVTRANSP: an unsophisticated pitch shifter, offering a range of one octave up and down. Really little more
than a demo of the fact it can be done at all!



Implementation details.


The plugins are based on 'pvoc' from the CARL distribution, adapted to use the FFTW libraries, 
for a significant speed increase. All the plugins use a 1024-sample FFT, with a double-length analysis 
window. For PVACCU and PVEXAG the overlap is 256 samples, so that plugin processes some 344  
FFT/IFFT pairs (analysis and resynthesis) per second at the 44100 sample rate.
 PVTRANSP uses a slighly small overlap of 160 samples, which offers a reasonable compromise 
between processing time and quality.


It is planned that the full sources for these plugins will be published soon, hopefully mostly under the GPL
(I am waiting for news of the CARL distribution moving to GPL; FFTW already is GPL).
Anyone wanting to build the plugins will need to download and install the FFTW libraries - 
see http://www.fftw.org. The plugins use the 32bit float verison of the libraries.


Richard Dobson
CDP
14th January:2001