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<H2>
deltap, deltapi</H2>
<PRE> ar <B>deltap</B> kdlt
ar <B>deltapi</B> xdlt</PRE>
<HR>
<H4>
<U>DESCRIPTION</U></H4>
Tap a delay line at variable offset times.
<H4>
<U>PERFORMANCE</U></H4>
These units can tap into a <B><A HREF="delayr.html">delayr/delayw</A></B>
pair, extracting delayed audio from the <I>idlt</I> seconds of stored sound.
There can be any number of <B>deltap</B> and/or <B>deltapi</B> units between
a read/write pair. Each receives an audio tap with no change of original
amplitude.
<P><B>deltap</B> extracts sound by reading the stored samples directly;
<B>deltapi</B> extracts sound by interpolated readout. By interpolating
between adjacent stored samples <B>deltapi</B> represents a particular
delay time with more accuracy, but it will take about twice as long to
run.
<P>The arguments <I>kdlt, xdlt</I> 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 <I>xdlt</I> argument in <B>deltapi</B> implies
that an audio-varying delay is permitted there.
<P>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 <B>deltap</B>. Medium-paced
or fast varying <I>dlt's</I>, however, will need the extra services of
<B>deltapi</B>.
<P><B>N.B.</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.
<H4>
<U>EXAMPLE:</U></H4>
<PRE> asource <B>buzz</B> 1, 440, 20, 1
atime <B>linseg</B> 1, p3/2,.01, p3/2,1 ; trace a distance in secs
ampfac <B>=</B> 1/atime/atime ; and calc an amp factor
adump <B>delayr</B> 1 ; set maximum distance
amove <B>deltapi</B> atime ; move sound source past
<B>delayw</B> asource ; the listener
<B>out</B> amove * ampfac</PRE>
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