Description

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.

<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

pvsanal, pvsynth, pvsadsyn

Credits

New plugin in version 5

November 2004.