Description

Clips an a-rate signal to a predefined limit, in a “soft” manner, using one of three methods.

Syntax

ares clip asig, imeth, ilimit [, iarg]

Initialization

imeth -- selects the clipping method. The default is 0. The methods are:

ilimit -- limiting value

iarg (optional, default=0.5) -- when imeth = 0, indicates the point at which clipping starts, in the range 0 - 1. Not used when imeth = 1 or imeth = 2. Default is 0.5.

Performance

asig -- a-rate input signal

The Bram de Jong method (imeth = 0) applies the algorithm (denoting ilimit as limit and iarg as a):

|x| >= 0 and |x| <= (limit*a):  f(x) = f(x)
|x| > (limit*a) and |x| <= limit:  f(x) = sign(x) * (limit*a+(x-limit*a)/(1+((x-limit*a)/(limit*(1-a)))2))
|x| > limit:  f(x) = sign(x) * (limit*(1+a))/2

The second method (imeth = 1) is the sine clip:

|x| < limit:  f(x) = limit * sin(π*x/(2*limit)),   |x| >= limit:  f(x) = limit * sign(x)

The third method (imeth = 2) is the tanh clip:

|x| < limit:  f(x) = limit * tanh(x/limit)/tanh(1),   |x| >= limit:  f(x) = limit * sign(x)

	Note
	Method 1 appears to be non-functional at release of Csound version 4.07.

Examples

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

<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 clip.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

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

instr 1	; white noise

arnd rand 1	; full amlitude
; Clip the noisy waveform's amplitude to 0.5
a1 clip arnd, 2, 0.5
   outs a1, a1

endin

instr 2	; white noise

arnd rand 1	; full amlitude
; Clip the noisy waveform's amplitude to 0.1
a1 clip arnd, 2, 0.1
   outs a1, a1

endin

</CsInstruments>
<CsScore>

; Play Instrument #1 for one second.
i 1 0 1
; Play Instrument #2 for one second.
i 2 1 1
e

</CsScore>
</CsoundSynthesizer>

Credits

New in Csound version 4.07

September 2009: Thanks to a note from Paolo Dell'Osso, corrected the formula.