Description

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 = 1
0dbfs = 1

;; example written by joachim heintz 2009

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
ktmpnt		linseg		0, p3, ilen; time pointer
fread 		pvsbufread  	ktmpnt, ibuffer; read the buffer
aout		pvsadsyn	fread, 10, 1; resynthesis with the first 10 bins
		out		aout
endin

</CsInstruments>
<CsScore>
i 1 0 1 20
e
</CsScore>
</CsoundSynthesizer>

See Also

pvsanal, pvsynth, pvsadsyn

Credits

New in version 4.13