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<H2><A ID="SECTION00665000000000000000">
Overlapping sample looper</A>
</H2>
<A ID="sect2.example.overlap"></A>
<P>
As described in Section <A HREF="node29.html#sect2.enveloping">2.3</A>, it is sometimes desirable to
use two or more overlapping looping samplers to produce a reasonably continuous
sound without having to envelope too sharply at the ends of the loop. This is
especially likely in situations where the chunk that is looped is short,
a tenth of a second or less. Example B10.sampler.overlap.pd, shown in Figure <A HREF="#fig02.16">2.16</A>
(part a), realizes two looping samplers a half-cycle out of phase from each
other. New object classes are:
<P>
<DIV ALIGN="CENTER"><A ID="fig02.16"></A><A ID="2466"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 2.16:</STRONG>
(a) two overlapped looping samplers (B10.sampler.overlap.pd); (b) the
same, but with a phasor-controlled read point (B11.sampler.rockafella.pd).</CAPTION>
<TR><TD><IMG
WIDTH="617" HEIGHT="741" BORDER="0"
SRC="img285.png"
ALT="\begin{figure}\psfig{file=figs/fig02.16.ps}\end{figure}"></TD></TR>
</TABLE>
</DIV>
<P>
<BR><!-- MATH
$\fbox{ $\mathrm{loadbang}$\ }$
-->
<IMG
WIDTH="87" HEIGHT="41" ALIGN="MIDDLE" BORDER="0"
SRC="img286.png"
ALT="\fbox{ $\mathrm{loadbang}$\ }">:
<A ID="2561"></A>output a "bang" message on load. This is used in this patch to make sure the
division of transposition by chunk size will have a valid transposition factor
in case "chunk size" is moused on first.
<P>
<BR><!-- MATH
$\fbox{ $\mathrm{expr}$\ }$
-->
<IMG
WIDTH="55" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
SRC="img287.png"
ALT="\fbox{ $\mathrm{expr}$\ }">:
<A ID="2562"></A>evaluate mathematical expressions. Variables appear as $f1, $f2, and so on,
corresponding to the object's inlets. Arithmetic operations are allowed,
with parentheses for grouping, and many library functions are supplied,
such as exponentiation, which shows up in this example as "pow" (the
power function).
<P>
<BR><!-- MATH
$\fbox{$\mathrm{wrap}\sim$}$
-->
<IMG
WIDTH="65" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
SRC="img288.png"
ALT="\fbox{$\mathrm{wrap}\sim$}">:
<A ID="2563"></A>wrap to the interval from 0 to 1. So, for instance, 1.2 becomes 0.2; 0.5
remains unchanged; and -0.6 goes to 0.4.
<P>
<BR><!-- MATH
$\fbox{ $\mathrm{send}\sim$\ }$
-->
<IMG
WIDTH="72" HEIGHT="41" ALIGN="MIDDLE" BORDER="0"
SRC="img289.png"
ALT="\fbox{ $\mathrm{send}\sim$\ }">,
<!-- MATH
$\fbox{ $\mathrm{s}\sim$\ }$
-->
<IMG
WIDTH="48" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
SRC="img290.png"
ALT="\fbox{ $\mathrm{s}\sim$\ }">,
<!-- MATH
$\fbox{ $\mathrm{receive}\sim$\ }$
-->
<IMG
WIDTH="88" HEIGHT="40" ALIGN="MIDDLE" BORDER="0"
SRC="img291.png"
ALT="\fbox{ $\mathrm{receive}\sim$\ }">,
<!-- MATH
$\fbox{ $\mathrm{r}\sim$\ }$
-->
<IMG
WIDTH="47" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
SRC="img292.png"
ALT="\fbox{ $\mathrm{r}\sim$\ }">:
<A ID="2564"></A><A ID="2565"></A><A ID="2566"></A><A ID="2567"></A>signal versions of <TT>send</TT> and <TT>receive</TT>. An audio
signal sent to a <TT>send~</TT> object appears at the outlets of any and
all <TT>receive~</TT> objects of the same name. Unlike
<TT>send</TT> and <TT>receive</TT>, you may not have more than one
<TT>send~</TT> object with the same name (in that connection, see
the <TT>throw~</TT> and <TT>catch~</TT> objects).
<P>
In the example, part of the wavetable reading machinery is duplicated, using
identical calculations of "chunk-size-samples" (a message stream) and
"read-pt" (an audio signal smoothed as before). However, the "phase"
audio signal, in the other copy, is replaced by "phase2". The top part
of the figure shows the calculation of the two phase signals: the first one
as the output of a <TT>phasor~</TT> object, and the second by adding
0.5 and wrapping, thereby adding 0.5 cycles (<IMG
WIDTH="13" HEIGHT="13" ALIGN="BOTTOM" BORDER="0"
SRC="img41.png"
ALT="$\pi $"> radians) to the
phase. The two phase signals are each used, with the same range adjustments as
before, to calculate indices into the wavetable and the <TT>cos~</TT> object, and to control the two <TT>samphold~</TT> objects. Finally, the
results of the two copies are added for output.
<P>
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<ADDRESS>
Miller Puckette
2006-12-30
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