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pvscale

Scale the frequency components of a pv stream, resulting in pitch shift.

Output amplitudes can be optionally modified in order to attempt formant preservation.

Syntax

fsig pvscale fsigin, kscal [, kkeepform, kgain, kcoefs]

Performance

fsig -- output pv stream

fsigin -- input pv stream

kscal -- scaling ratio.

kkeepform -- attempt to keep input signal formants; 0: do not keep formants; 1: keep formants using a liftered cepstrum method; 2: keep formants by using a true envelope method (defaults to 0).

kgain -- amplitude scaling (defaults to 1).

kcoefs -- number of cepstrum coefs used in formant preservation (defaults to 80).

The quality of the pitch shift will be improved with the use of a Hanning window in the pvoc analysis. Formant preservation method 1 is less intensive than method 2, which might not be suited to realtime use.

⚠ Warning

It is unsafe to use the same f-variable for both input and output of pvs opcodes. Using the same one might lead to undefined behavior on some opcodes. Use a different one on the left and right sides of the opcode.

Examples

asig  in                                 ; get the signal in

fsig  pvsanal   asig, 1024, 256, 1024, 1 ; analyse it
ftps  pvscale   fsig, 1.5, 1, 1          ; transpose it keeping formants
atps  pvsynth   ftps                     ; synthesise it

adp   delayr    0.1                      ; delay original signal
adel  deltapn   1024                     ; by 1024 samples
      delayw    asig
      out       atps + adel              ; add tranposed and original

The example above shows a vocal harmoniser. The delay is necessary to time-align the signals, as the analysis-synthesis process will imply a delay of 1024 samples between the analysis input and the synthesis output.

Here is an example of the use of the pvscale opcode. It uses the file pvscale.csd.

Example of the _pvscale_ opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
; Audio out   Audio in
-odac    ;;;RT audio I/O
; For Non-realtime ouput leave only the line below:
; -o pvscale.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs  = 1

;; example written by joachim heintz 2009

instr 1
ifftsize        = 1024
ioverlap        = ifftsize / 4
iwinsize        = ifftsize
iwinshape       = 1; von-Hann window
Sfile           = "fox.wav"
ain             soundin Sfile
fftin           pvsanal ain, ifftsize, ioverlap, iwinsize, iwinshape; fft-analysis of the audio-signal
fftblur     pvscale     fftin, p4, p5, p6; scale
aout            pvsynth fftblur; resynthesis
outs            aout*.5, aout*.5
endin

</CsInstruments>
<CsScore>
i 1 0 3 1 0 1   ; original sound
i 1 3 3 1.5 0 2 ; fifth higher without ...
i 1 6 3 1.5 1 2 ; ... and with different ...
i 1 9 3 1.5 2 5 ; ... kinds of formant preservation
e
</CsScore>
</CsoundSynthesizer>

See also

Tools for Real-time Spectral Processing (pvs opcodes)

Credits

Author: Victor Lazzarini
November 2004

New plugin in version 5

November 2004.