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pvshift

Shift the frequency components of a pv stream, stretching/compressing its spectrum.

Syntax

fsig pvshift fsigin, kshift, klowest [, kkeepform, igain, kcoefs]

Performance

fsig -- output pv stream

fsigin -- input pv stream

kshift -- shift amount (in Hz, positive or negative).

klowest -- lowest frequency to be shifted.

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).

This opcode will shift the components of a pv stream, from a certain frequency upwards, up or down a fixed amount (in Hz). It can be used to transform a harmonic spectrum into an inharmonic one. The kkeepform flag can be used to try and preserve formants for possibly interesting and unusual spectral modifications.

⚠ 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  pvshift   fsig, 100, 0             ; add 100 Hz to each component
atps  pvsynth   ftps                     ; synthesise it

Depending on the input, this will transform a pitched sound into an inharmonic, bell-like sound.

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

Example of the _pvshift_ opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac  ;;;realtime audio out
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o pvshift.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
ishift          = p4    ; shift amount in Hz
ilowest         = p5    ; lowest frequency to be shifted
ikeepform       = p6    ; 0=no formant keeping, 1=keep by amps, 2=keep by spectral envelope
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 file
fshift          pvshift         fftin, ishift, ilowest, ikeepform; shift frequencies
aout            pvsynth fshift; resynthesize
                outs    aout, aout
endin

</CsInstruments>
<CsScore>
i 1 0 2.757 0 0 0; no shift at all
i 1 3 2.757 100 0 0; shift all frequencies by 100 Hz
i 1 6 2.757 200 0 0; by 200 Hz
i 1 9 2.757 200 0 1; keep formants by method 1
i 1 12 2.757 200 0 2; by method 2
i 1 15 2.757 200 1000 0; shift by 200 Hz but just above 1000 Hz
i 1 18 2.757 1000 500 0; shift by 1000 Hz above 500 Hz
i 1 21 2.757 1000 300 0; above 300 Hz
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.