pvsadsyn

Resynthesize using a fast oscillator-bank.

Syntax

ares pvsadsyn fsrc, inoscs, kfmod [, ibinoffset] [, ibinincr] [, iinit]

Initialization

inoscs -- The number of analysis bins to synthesise. Cannot be larger than the size of fsrc (see pvsinfo), e.g. as created by pvsanal. Processing time is directly proportional to inoscs.

ibinoffset (optional, default=0) -- The first (lowest) bin to resynthesise, counting from 0 (default = 0).

ibinincr (optional) -- Starting from bin ibinoffset, resynthesize bins ibinincr apart.

iinit (optional) -- Skip reinitialization. This is not currently implemented for any of these opcodes, and it remains to be seen if it is even practical.

Performance

kfmod -- Scale all frequencies by factor kfmod. 1.0 = no change, 2 = up one octave.

pvsadsyn is experimental, and implements the oscillator bank using a fast direct calculation method, rather than a lookup table. This takes advantage of the fact, empirically arrived at, that for the analysis rates generally used, (and presuming analysis using pvsanal, where frequencies in a bin change only slightly between frames) it is not necessary to interpolate frequencies between frames, only amplitudes. Accurate resynthesis is often contingent on the use of pvsanal with iwinsize = ifftsize*2.

This opcode is the most likely to change, or be much extended, according to feedback and advice from users. It is likely that a full interpolating table-based method will be added, via a further optional iarg. The parameter list to pvsadsyn mimics that for pvadd, but excludes spectral extraction.

Examples

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

<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 pvsadsyn.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 16
nchnls = 2
0dbfs = 1

;; example written by joachim heintz 2009
; (additions by Menno Knevel 2021)
opcode FileToPvsBuf, iik, Siiii
;;writes an audio file at the first k-cycle to a fft-buffer (via pvsbuffer)
Sfile, ifftsize, ioverlap, iwinsize, iwinshape xin
ktimek          timeinstk
if ktimek == 1 then
ilen            filelen Sfile
kcycles =               ilen * kr; number of k-cycles to write the fft-buffer
kcount          init            0
loop:
ain             soundin Sfile
fftin           pvsanal ain, ifftsize, ioverlap, iwinsize, iwinshape
ibuf, ktim      pvsbuffer       fftin, ilen + (ifftsize / sr)
                loop_lt kcount, 1, kcycles, loop
                xout            ibuf, ilen, ktim
endif
endop


instr 1
istretch        =               p4; time stretching factor
ifftsize        =               1024
ioverlap        =               ifftsize / 4
iwinsize        =               ifftsize
iwinshape       =               1; von-Hann window
ibuffer, ilen, k0               FileToPvsBuf    "fox.wav", ifftsize, ioverlap, iwinsize, iwinshape
p3              =               istretch * ilen; set p3 to the correct value
prints  "--**new duration of note = %f seconds**--\n", p3
ktmpnt          linseg          0, p3, ilen; time pointer
fread           pvsbufread      ktmpnt, ibuffer; read the buffer
aout            pvsadsyn        fread, 50, 1, p5; resynthesis of 50 bins, with offset p5
aout        *=  .7      ; scale amplitude
                outs            aout, aout
endin

</CsInstruments>
<CsScore>
;         stretch   offset  
i 1  0 1    10        0
i 1 28 1    5        30
e
</CsScore>
</CsoundSynthesizer>

See also

Tools for Real-time Spectral Processing (pvs opcodes)

Credits

Author: Richard Dobson
August 2001

New in version 4.13