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.

Param Field Parameter Units Dynamic Optional Notes
p0 output start time seconds no no  
p1 input start time seconds no no  
p2 input duration seconds no no  
p3 pre-amp multiplier (before decimation) relative multiplier yes no  
p4 post-amp multiplier (after decimation) relative multiplier yes no  
p5 number of bits to use 1 to 16 yes no  
p6 low-pass filter cutoff frequency Hz yes yes default: 0 (will bypass)
p7 input channel - no yes default: 0
p8 pan 0-1 stereo; 0.5 is middle yes yes default: 0

Parameters labled as Dynamic can receive dynamic updates from a table or real-time control source.

Author: 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)


   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)
   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