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pvread

Reads from a pvoc file and returns the frequency and amplitude from a single analysis channel or bin.

The returned values can be used anywhere else in the Csound instrument. For example, one can use them as arguments to an oscillator to synthesize a single component from an analyzed signal or a bank of pvreads can be used to resynthesize the analyzed sound using additive synthesis by passing the frequency and magnitude values to a bank of oscillators.

Syntax

kfreq, kamp = pvread(ktimpnt, ifile, ibin [, ifiletime])

kfreq, kamp pvread ktimpnt, ifile, ibin [, ifiletime]

Initialization

ifile -- the pvoc number (n in pvoc.n) or the name in quotes of the analysis file made using pvanal. (See pvoc.)

ibin -- the number of the analysis channel from which to return frequency in Hz and magnitude.

ifiletime (optional, default=0) -- zero keeps the original time mapping, which uses Csound's output sample rate to convert ktimpnt to a file frame. Set to 1 to use the analysis file's sample rate instead, so ktimpnt refers to seconds in the source recording. The modes differ only when those sample rates differ.

Performance

kfreq, kamp -- outputs of the pvread unit. These values, retrieved from a phase vocoder analysis file, represent the values of frequency and amplitude from a single analysis channel specified in the ibin argument. Interpolation between analysis frames is performed at k-rate resolution and dependent of course upon the rate and direction of ktimpnt.

ktimpnt -- the passage of time, in seconds, through this file. ktimpnt must always be positive, but can move forwards or backwards in time, be stationary or discontinuous, as a pointer into the analysis file.

For a 22,050 Hz analysis file played by Csound at 44,100 Hz, the default mode reads the frame at file time 2 seconds when ktimpnt is 1. With kfreq, kamp pvread 1, "source.pvx", 2, 1, it reads file time 1 second.

Examples

The example below shows the use pvread to synthesize a single component at a time from a phase vocoder analysis file. It should be noted that the kfreq and kamp outputs can be used for any kind of synthesis, filtering, processing, and so on.

Example of the pvread opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac   -m0  --limiter=.95 ;;;realtime audio out, with limiter protection
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o pvread.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

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

; by Menno Knevel 2021

gilen  filelen "fox.wav"            ; get length of impulse soundfile

; analyze sound file and output result to pvoc-ex file
ires system_i 1,{{ pvanal fox.wav fox1.pvx }}          ; default settings

instr 1 ; untreated signal
asig    diskin2   "fox.wav", 1
prints  "\n---***YOU NOW HEAR THE UNTREATED SOUND SAMPLE***---\n"
outs    asig, asig
endin

instr 2

prints  "\n---***YOU NOW HEAR THE RESULT OF THIS ANALYZED FILE:***---\n"
ibin  = p4
ktime line 0, p3, 2.8
kfreq, kamp pvread ktime, "fox1.pvx", ibin      ;read data from 7th analysis bin.
asig  poscil kamp, kfreq
      outs asig*5, asig*5                               ;compensate loss of volume

endin
</CsInstruments>
<CsScore>

i1 0 2.76           ; original sample
s
i2 0 2.76   7       ; 3 different bins
i2 + 2.76   15
i2 + 2.76   25
s
i2 2 6      7       ; slow chord
i2 2 6      50
i2 2 2      75
e
</CsScore>
</CsoundSynthesizer>

See Also

Short-time Fourier Transform (STFT) Resynthesis

Credits

Author: Richard Karpen
Seattle, Wash
1997

New in version 3.44