pvswarp

Warp the spectral envelope of a PVS signal by means of shifting and scaling.

Syntax

fsig pvswarp fsigin, kscal, kshift [, klowest, kmeth, kgain, kcoefs]

Performance

fsig -- output pv stream

fsigin -- input pv stream

kscal -- spectral envelope scaling ratio. Values > 1 stretch the envelope and < 1 compress it.

kshift -- spectral envelope shift (in Hz), values > 0 shift the envelope linearly upwards and values < 0 shift it downwards.

klowest -- lowest frequency shifted (affects only kshift, defaults to 0).

kmethod -- spectral envelope extraction method. 1: liftered cepstrum method; 2: true envelope method (defaults to 1).

kgain -- amplitude scaling (defaults to 1).

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

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

Here is an example of the pvswarp opcode. It uses the file pvswarp.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 pvswarp.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

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

instr 1

kscal = p4
kshift = p5
asig  soundin "fox.wav"                 ; get the signal in
fsig  pvsanal asig, 1024, 256, 1024, 1  ; analyse it
ftps  pvswarp fsig, kscal, kshift               ; warp it
atps  pvsynth ftps                      ; synthesise it                      
      outs atps/2, atps/2

endin
</CsInstruments>
<CsScore>
 ;change scale
i 1 0 3 1
i 1 + . 1.5
i 1 + . 3
i 1 + . .25
 ;change shift
i 1 + . 1 0
i 1 + . . 300
i 1 + . . 0
i 1 + . . -300
e
</CsScore>
</CsoundSynthesizer>

Used with vocal sounds, it will shift the formants and result in a changed vowel timbre, similar to the effect of a singer inhaling helium (the 'donald duck' effect).

See also

Tools for Real-time Spectral Processing (pvs opcodes)

Credits

Author: Victor Lazzarini
November 2004

New plugin in version 5

November 2004.