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resonx

Emulates a stack of filters using the reson opcode.

resonx is equivalent to a filters consisting of more layers of reson with the same arguments, serially connected. Using a stack of a larger number of filters allows a sharper cutoff. They are faster than using a larger number instances in a Csound orchestra of the old opcodes, because only one initialization and k- cycle are needed at time and the audio loop falls entirely inside the cache memory of processor.

Syntax

ares resonx asig, xcf, xbw [, inumlayer] [, iscl] [, iskip]

Initialization

inumlayer (optional) -- number of elements in the filter stack. Default value is 4.

iscl (optional, default=0) -- coded scaling factor for resonators. A value of 1 signifies a peak response factor of 1, i.e. all frequencies other than kcf are attenuated in accordance with the (normalized) response curve. A value of 2 raises the response factor so that its overall RMS value equals 1. (This intended equalization of input and output power assumes all frequencies are physically present; hence it is most applicable to white noise.) A zero value signifies no scaling of the signal, leaving that to some later adjustment (see balance). The default value is 0.

iskip (optional, default=0) -- initial disposition of internal data space. Since filtering incorporates a feedback loop of previous output, the initial status of the storage space used is significant. A zero value will clear the space; a non-zero value will allow previous information to remain. The default value is 0.

Performance

asig -- input signal

xcf -- the center frequency of the filter, or frequency position of the peak response.

xbw -- bandwidth of the filter (the Hz difference between the upper and lower half-power points)

Examples

Here is an example of the resonx opcodes. It uses the file resonx.csd.

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

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

instr 1 ; unfiltered noise

kenv    linseg  0, p3*.5, 1, p3*.5, 0   ;envelope
asig    rand    0.7                     ;white noise
        outs    asig*kenv, asig*kenv

endin

instr 2 ; filtered noise

kenv    linseg  0, p3*.5, 1, p3*.5, 0   ;envelope
asig    rand    0.7
kcf     line    300, p3, 2000
afilt   resonx  asig, kcf, 300, 4
asig    balance afilt, asig
        outs    asig*kenv, asig*kenv

endin
</CsInstruments>
<CsScore>

i 1 0 2
i 2 3 2

e
</CsScore>
</CsoundSynthesizer>

See also

Standard Filters: Resonant Low-pass filters

Credits

Author: Gabriel Maldonado (adapted by John ffitch)
Italy

New in Csound version 3.49

Audio rate parameters introduced in version 6.02

November 2013.