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deltap, deltapi

     ar   deltap    kdlt
     ar   deltapi   xdlt


Tap a delay line at variable offset times.


These units can tap into a delayr/delayw pair, extracting delayed audio from the idlt seconds of stored sound. There can be any number of deltap and/or deltapi units between a read/write pair. Each receives an audio tap with no change of original amplitude.

deltap extracts sound by reading the stored samples directly; deltapi extracts sound by interpolated readout. By interpolating between adjacent stored samples deltapi represents a particular delay time with more accuracy, but it will take about twice as long to run.

The arguments kdlt, xdlt specify the tapped delay time in seconds. Each can range from 1 Control Period to the full delay time of the read/write pair; however, since there is no internal check for adherence to this range, the user is wholly responsible. Each argument can be a constant, a variable, or a time-varying signal; the xdlt argument in deltapi implies that an audio-varying delay is permitted there.

These units can provide multiple delay taps for arbitrary delay path and feedback networks. They can deliver either constant-time or time-varying taps, and are useful for building chorus effects, harmonizers, and doppler shifts. Constant-time delay taps (and some slowly changing ones) do not need interpolated readout; they are well served by deltap. Medium-paced or fast varying dlt's, however, will need the extra services of deltapi.

N.B. K-rate delay times are not internally interpolated, but rather lay down stepped time-shifts of audio samples; this will be found quite adequate for slowly changing tap times. For medium to fastpaced changes, however, one should provide a higher resolution audio-rate timeshift as input.


  asource   buzz      1, 440, 20, 1 
  atime     linseg    1, p3/2,.01, p3/2,1 ; trace a distance in secs
  ampfac    =         1/atime/atime  ;     and calc an amp factor
  adump     delayr    1              ; set maximum distance 
  amove     deltapi   atime          ; move sound source past
            delayw    asource        ;     the listener
            out       amove * ampfac

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