pvsbandr

A band reject filter working in the spectral domain.

Filter the pvoc frames, rejecting bins whose frequency is within a band, and with linear interpolation for transitional bands.

Syntax

fsig pvsbandr fsigin, xlowcut, xlowfull, xhighfull, xhighcut [, ktype]

Performance

fsig -- output pv stream

fsigin -- input pv stream.

xlowcut, xlowfull, xhighfull, xhighcut -- define a trapezium shape for the band that is rejected. The a-rate versions only apply to the sliding case.

ktype -- specifies the shape of the transitional band. If at the default value of zero the shape is as below, with linear transition in amplitude. Other values give an exponential curve

(1 - exp( r*type )) / (1 - exp(type))

This includes a linear dB shape when ktype is log(10) or about 2.30.

The opcode performs a band-reject filter with a spectral envelope shaped like

        klowcut                       khighcut
________                                      ______________
        \                                    /
         \                                  /
          \                                /
           \                              /  
            \                            /    
     klowfull\__________________________/ khighfull

Examples

Here is an example of the pvsbandr opcode. It uses the file pvsbandr.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 pvsbandr.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
Sfile           =               "fox.wav"
klowcut = 100
klowfull = p4
khighfull = p5
khighcut = 2000
ain             soundin Sfile
fftin           pvsanal ain, 1024, 256, 1024, 1; fft-analysis of the audio-signal
fftbp           pvsbandr        fftin, klowcut, klowfull, khighfull, khighcut ; band reject
abp             pvsynth fftbp; resynthesis
                outs            abp, abp
endin


</CsInstruments>
<CsScore>
;         lowfull highfull
i 1 0 3     200     1900     
i 1 + 3     100     1500
e
</CsScore>
</CsoundSynthesizer>

See also

Tools for Real-time Spectral Processing (pvs opcodes)

Credits

Author: John ffitch
December 2007