an open-source digital signal processing and sound synthesis language
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DISTORT -- non-linear distortion of an input signal
in RTcmix/insts/jg


quick syntax:
DISTORT(outsk, insk, dur, AMP, disttype, PREAMP, LOWPASSFREQ[, inputchan, PAN, BYPASS])

CAPITALIZED parameters are pfield-enabled for table or dynamic control (see the maketable or makeconnection scorefile commands). Parameters after the [bracket] are optional and default to 0 unless otherwise noted.



   p0 = output start time (seconds)
   p1 = input start time (seconds)
   p2 = input duration (seconds)
   p3 = amplitude multiplier (relative multiplier of input signal)
   p4 = type of distortion (1: soft clip, 2: tube)
   p5 = gain (before distortion) (relative multiplier)
   p6 = cutoff freq for low-pass filter (Hz)  (0 to disable filter)
   p7 = input channel [optional; default is 0]
   p8 = percent to left channel [optional; default is .5]
   p9 = bypass (0: bypass off, 1: bypass on) [optional; default is 0]

   p3 (amplitude), p5 (gain), p6 (cutoff), p8 (pan) and p9 (bypass) can
   receive dynamic updates from a table or real-time control source.

   Author: John Gibson (johgibso at indiana dot edu), 8/12/03, rev for v4, 7/10/04.



DISTORT applies waveshaping (clipping) distortion and an optional lowpass filter to an input sound

Usage Notes

DISTORT will apply a non-linear distortion algoritm ("clipping") to an input sound and then (optionally) lowpass filter the result. The distortion algorithm used is taken from the STRUM instrument, code originally written by Charles Sullivan. DISTORT is similar in action to SHAPE.

The "tube" setting for p4 ("disttype") doesn't work correctly yet.

The optional low-pass filter (p6 > 0) is a simple butterworth filter design. The cutoff frequency may be modulated dynamically. The filter comes after the distortion in the signal chain.

DISTORT can produce either mono or stereo output.

Sample Scores

very basic:
   rtsetparams(44100, 2)
   load("DISTORT")

   rtinput("AUDIO")
   
   // distort output
   type = 1   // 1: soft clip, 2: tube
   amp = 1.0
   ampenv = maketable("line", 1000, 0,0, 2,1, 4,1, 5,0)
   gain = 10.0
   cf = 2000 // lowpass filter
   DISTORT(0, 0, 5.0, amp*ampenv, type, gain, cf, 0, 1)
   DISTORT(0.2, 0, 5.0, amp*ampenv, type, gain, cf, 0, 0)


slightly more advanced:
   rtsetparams(44100, 2)
   load("WAVETABLE")
   load("DISTORT")
   
   bus_config("WAVETABLE", "aux 0 out")
   bus_config("DISTORT", "aux 0 in", "out 0-1")
   
   dur = 6.0
   amp = 10000
   pitch = 7.00
   wavetable = maketable("wave", 1000, 
      1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/7, 1/8, 1/9, 1/10, 1/11, 1/12,
      1/13, 1/14, 1/15, 1/16, 1/18, 1/19, 1/20, 1/21, 1/22, 1/23, 1/24)  // saw
   reset(10000) 
   WAVETABLE(0, dur, amp, pitch, 0, wavetable)
   WAVETABLE(0, dur, amp, pitch+.0002, 0, wavetable)
   
   // distort wavetable output
   bypass = 0
   type = 1   // 1: soft clip, 2: tube
   amp = 1.2
   ampenv = maketable("line", 1000, 0,0, 1,1, 7,1, 10,0)
   gain = 30.0
   cf = 0
   DISTORT(0, 0, dur, amp*ampenv, type, gain, cf, 0, 1, bypass)
   DISTORT(0.2, 0, dur, amp*ampenv, type, gain, cf, 0, 0, bypass)


See Also

BUTTER, COMPLIMIT, DECIMATE, SHAPE, STRUMFB, WAVESHAPE