an open-source digital signal processing and sound synthesis language
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DECIMATE -- bit-reduce an input signal
in RTcmix/insts/jg


quick syntax:
DECIMATE(outsk, insk, dur, PREAMP, POSTAMP, NBITS[, LOWPASSFREQ, inputchan, PAN])

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 = pre-amp multiplier (before decimation) (relative multiplier)
   p4 = post-amp multiplier (after decimation) (relative multiplier)
   p5 = number of bits to use (1 to 16)
   p6 = low-pass filter cutoff frequency (or 0 to bypass) [optional, default is 0]
   p7 = input channel [optional, default is 0]
   p8 = pan (0-1 stereo; 0.5 is middle) [optional; default is 0]

   p3 (pre-amp), p4 (post-amp), p5 (bits), p6 (cutoff) and p8 (pan) can
   receive dynamic updates from a table or real-time control source.

   JGG , 3 Jan 2002, rev for v4, 7/11/04



DECIMATE reduces the number of bits in the input audio signal

Usage Notes

DECIMATE reduces the number of bits used to represent the amplitude of individual samples. The sound quality will be altered as a result

The optional low-pass filter (p5 > 0) is a simple butterworth filter design. The cutoff frequency may be modulated dynamically.

The "PREAMP" (p3) and "POSTAMP" (p4) parameters allow you to adjust the alteration in amplitude resulting from the bit-rediction.

The output of DECIMATE can be either mono or stereo.

Sample Scores

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

   rtinput("mysound.aif")

   bits = 2
   cutoff = 4000
   dur = DUR()
   amp = 1
   ampenv = maketable("line", 1000, 0,0, 1,1, 5,1, 10,0)

   DECIMATE(0, 0, dur, 1, amp*ampenv, bits, cutoff)


slightly more advanced:
   rtsetparams(44100, 2)
   load("DECIMATE")
   
   rtinput("mysound.aif")
   
   inchan = 0
   dur = DUR()
   
   bits = 2
   preamp = 2
   postamp = maketable("line", 1000, 0,0, 5,1, 9,1, 10,0)
   cutoff = maketable("line", "nonorm", 1000, 0,1, 1,10000, 2,800)
   pan = maketable("line", 100, 0,0, 1,1)
   
   DECIMATE(0, 0, dur, preamp, 0.9*postamp, bits, cutoff, inchan, pan)


See Also

BUTTER, COMPLIMIT, COMPLIMIT, DISTORT, SHAPE