butterlp

butterlp — A low-pass Butterworth filter.

Description

Implementation of a second-order low-pass Butterworth filter. This opcode can also be written as butlp.

Syntax

ares butterlp asig, kfreq [, iskip]

Initialization

iskip (optional, default=0) -- Skip initialization if present and non-zero.

Performance

These filters are Butterworth second-order IIR filters. They are slightly slower than the original filters in Csound, but they offer an almost flat passband and very good precision and stopband attenuation.

asig -- Input signal to be filtered.

kfreq -- Cutoff or center frequency for each of the filters.

Examples

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

Example 91. Example of the butterlp opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac     ;;;RT audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o butterlp.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

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

instr 1	; White noise signal

asig rand 0.5
     outs asig, asig

endin



instr 2	; filtered noise

asig rand 0.7
alp  butterlp asig, 1000	  ;cutting frequencies above 1 KHz
     outs alp, alp

endin

</CsInstruments>
<CsScore>

i 1 0 2
i 2 2.5 2
e

</CsScore>
</CsoundSynthesizer>


See Also

butterbp, butterbr, butterhp

Credits

Author: Paris Smaragdis
MIT, Cambridge
1995

Existed in 3.30