202 lines
7.5 KiB
HTML
202 lines
7.5 KiB
HTML
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|
||
|
|
|
||
|
|
<!--Converted with LaTeX2HTML 2002-2-1 (1.71)
|
||
|
|
original version by: Nikos Drakos, CBLU, University of Leeds
|
||
|
|
* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
|
||
|
|
* with significant contributions from:
|
||
|
|
Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
|
||
|
|
<HTML>
|
||
|
|
<HEAD>
|
||
|
|
<TITLE>Constant amplitude scaler</TITLE>
|
||
|
|
<META NAME="description" CONTENT="Constant amplitude scaler">
|
||
|
|
<META NAME="keywords" CONTENT="book">
|
||
|
|
<META NAME="resource-type" CONTENT="document">
|
||
|
|
<META NAME="distribution" CONTENT="global">
|
||
|
|
|
||
|
|
<META NAME="Generator" CONTENT="LaTeX2HTML v2002-2-1">
|
||
|
|
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">
|
||
|
|
|
||
|
|
<LINK REL="STYLESHEET" HREF="book.css">
|
||
|
|
|
||
|
|
<LINK REL="next" HREF="node20.html">
|
||
|
|
<LINK REL="previous" HREF="node18.html">
|
||
|
|
<LINK REL="up" HREF="node18.html">
|
||
|
|
<LINK REL="next" HREF="node20.html">
|
||
|
|
</HEAD>
|
||
|
|
|
||
|
|
<BODY >
|
||
|
|
<!--Navigation Panel-->
|
||
|
|
<A NAME="tex2html825"
|
||
|
|
HREF="node20.html">
|
||
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/next.png"></A>
|
||
|
|
<A NAME="tex2html819"
|
||
|
|
HREF="node18.html">
|
||
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/up.png"></A>
|
||
|
|
<A NAME="tex2html813"
|
||
|
|
HREF="node18.html">
|
||
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/prev.png"></A>
|
||
|
|
<A NAME="tex2html821"
|
||
|
|
HREF="node4.html">
|
||
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/contents.png"></A>
|
||
|
|
<A NAME="tex2html823"
|
||
|
|
HREF="node201.html">
|
||
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/index.png"></A>
|
||
|
|
<BR>
|
||
|
|
<B> Next:</B> <A NAME="tex2html826"
|
||
|
|
HREF="node20.html">Amplitude control in decibels</A>
|
||
|
|
<B> Up:</B> <A NAME="tex2html820"
|
||
|
|
HREF="node18.html">Examples</A>
|
||
|
|
<B> Previous:</B> <A NAME="tex2html814"
|
||
|
|
HREF="node18.html">Examples</A>
|
||
|
|
<B> <A NAME="tex2html822"
|
||
|
|
HREF="node4.html">Contents</A></B>
|
||
|
|
<B> <A NAME="tex2html824"
|
||
|
|
HREF="node201.html">Index</A></B>
|
||
|
|
<BR>
|
||
|
|
<BR>
|
||
|
|
<!--End of Navigation Panel-->
|
||
|
|
|
||
|
|
<H2><A NAME="SECTION00591000000000000000">
|
||
|
|
Constant amplitude scaler</A>
|
||
|
|
</H2>
|
||
|
|
|
||
|
|
<P>
|
||
|
|
Example A01.sinewave.pd, shown in Figure <A HREF="#fig01.11">1.11</A>, contains essentially the
|
||
|
|
simplest possible patch that makes a sound,
|
||
|
|
with only three object boxes. (There are also comments, and two message
|
||
|
|
boxes to turn Pd's ``DSP" (audio) processing on and off.) The three object boxes
|
||
|
|
are:
|
||
|
|
|
||
|
|
<P>
|
||
|
|
|
||
|
|
<DIV ALIGN="CENTER"><A NAME="fig01.11"></A><A NAME="1256"></A>
|
||
|
|
<TABLE>
|
||
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 1.11:</STRONG>
|
||
|
|
The contents of the first Pd example patch: A01.sinewave.pd.</CAPTION>
|
||
|
|
<TR><TD><IMG
|
||
|
|
WIDTH="542" HEIGHT="608" BORDER="0"
|
||
|
|
SRC="img145.png"
|
||
|
|
ALT="\begin{figure}\psfig{file=figs/fig01.11.ps}\end{figure}"></TD></TR>
|
||
|
|
</TABLE>
|
||
|
|
</DIV>
|
||
|
|
|
||
|
|
<P>
|
||
|
|
<BR><!-- MATH
|
||
|
|
$\fbox{ $ \mathrm{osc}\sim $}$
|
||
|
|
-->
|
||
|
|
<IMG
|
||
|
|
WIDTH="57" HEIGHT="33" ALIGN="MIDDLE" BORDER="0"
|
||
|
|
SRC="img146.png"
|
||
|
|
ALT="\fbox{ $ \mathrm{osc}\sim $}">:
|
||
|
|
<A NAME="1402"></A>sinusoidal oscillator. The
|
||
|
|
left hand side input
|
||
|
|
and the output are digital audio signals. The input is taken to be a
|
||
|
|
(possibly time-varying) frequency in Hertz. The output is a sinusoid at
|
||
|
|
the specified frequency. If nothing is connected to the frequency inlet,
|
||
|
|
the creation argument (440 in this example) is used as the frequency.
|
||
|
|
The output has peak amplitude one. You may set an initial phase by sending
|
||
|
|
messages (not audio signals) to the right inlet. The left (frequency) inlet
|
||
|
|
may also be sent messages to set the frequency, since any inlet that takes an
|
||
|
|
audio signal may also be sent messages which are automatically converted to the
|
||
|
|
desired audio signal.
|
||
|
|
|
||
|
|
<P>
|
||
|
|
<BR><!-- MATH
|
||
|
|
$\fbox{ $*\sim$\ }$
|
||
|
|
-->
|
||
|
|
<IMG
|
||
|
|
WIDTH="49" HEIGHT="34" ALIGN="MIDDLE" BORDER="0"
|
||
|
|
SRC="img147.png"
|
||
|
|
ALT="\fbox{ $*\sim$\ }">:
|
||
|
|
<A NAME="1370"></A>multiplier. This exists in two
|
||
|
|
forms. If a creation argument is specified (as in this example; it's 0.05),
|
||
|
|
this box multiplies a digital audio signal (in the left inlet) by the number;
|
||
|
|
messages to the right inlet can update the number as well. If no argument is
|
||
|
|
given, this box multiplies two incoming digital audio signals together.
|
||
|
|
|
||
|
|
<P>
|
||
|
|
<BR><!-- MATH
|
||
|
|
$\fbox{ $ \mathrm{dac}\sim $}$
|
||
|
|
-->
|
||
|
|
<IMG
|
||
|
|
WIDTH="60" HEIGHT="41" ALIGN="MIDDLE" BORDER="0"
|
||
|
|
SRC="img148.png"
|
||
|
|
ALT="\fbox{ $ \mathrm{dac}\sim $}">:
|
||
|
|
<A NAME="1403"></A>audio output device.
|
||
|
|
Depending on your hardware, this might not actually be a Digital/Analog
|
||
|
|
Converter as the name suggests; but in general, it allows you to send any
|
||
|
|
audio signal to your computer's audio output(s). If there are no creation
|
||
|
|
arguments, the default behavior is to output to channels one and two of
|
||
|
|
the audio hardware; you may specify alternative channel numbers (one or many)
|
||
|
|
using the creation arguments. Pd itself may be configured to use two or
|
||
|
|
more output channels, or may not have the audio output device open at all;
|
||
|
|
consult the Pd documentation for details.
|
||
|
|
|
||
|
|
<P>
|
||
|
|
The two message boxes show a peculiarity in the way messages are parsed in
|
||
|
|
message boxes. Earlier in Figure <A HREF="node16.html#fig01.10">1.10</A> (part a), the message
|
||
|
|
consisted only of the number 21. When clicked, that box sent the message ``21"
|
||
|
|
to its outlet and hence to any objects connected to it. In this current
|
||
|
|
example, the text of the message boxes starts with a semicolon. This is a
|
||
|
|
terminator between messages (so the first message is empty), after which the
|
||
|
|
next word is taken as the name of the recipient of the following message. Thus
|
||
|
|
the message here is ``dsp 1" (or ``dsp 0") and the message is to be sent, not
|
||
|
|
to any connected objects--there aren't any anyway--but rather, to the object
|
||
|
|
named ``pd". This particular object is provided invisibly by the Pd program
|
||
|
|
and you can send it various messages to control Pd's global state, in this case
|
||
|
|
turning audio processing on (``1") and off (``0").
|
||
|
|
|
||
|
|
<P>
|
||
|
|
Many more details about the control aspects of Pd, such as the above, are
|
||
|
|
explained in a different series of example patches (the ``control examples") in
|
||
|
|
the Pd release, but they will only be touched on here as necessary to
|
||
|
|
demonstrate the audio signal processing techniques that are the subject of this
|
||
|
|
book.
|
||
|
|
|
||
|
|
<P>
|
||
|
|
<HR>
|
||
|
|
<!--Navigation Panel-->
|
||
|
|
<A NAME="tex2html825"
|
||
|
|
HREF="node20.html">
|
||
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/next.png"></A>
|
||
|
|
<A NAME="tex2html819"
|
||
|
|
HREF="node18.html">
|
||
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/up.png"></A>
|
||
|
|
<A NAME="tex2html813"
|
||
|
|
HREF="node18.html">
|
||
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/prev.png"></A>
|
||
|
|
<A NAME="tex2html821"
|
||
|
|
HREF="node4.html">
|
||
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/contents.png"></A>
|
||
|
|
<A NAME="tex2html823"
|
||
|
|
HREF="node201.html">
|
||
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
||
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/index.png"></A>
|
||
|
|
<BR>
|
||
|
|
<B> Next:</B> <A NAME="tex2html826"
|
||
|
|
HREF="node20.html">Amplitude control in decibels</A>
|
||
|
|
<B> Up:</B> <A NAME="tex2html820"
|
||
|
|
HREF="node18.html">Examples</A>
|
||
|
|
<B> Previous:</B> <A NAME="tex2html814"
|
||
|
|
HREF="node18.html">Examples</A>
|
||
|
|
<B> <A NAME="tex2html822"
|
||
|
|
HREF="node4.html">Contents</A></B>
|
||
|
|
<B> <A NAME="tex2html824"
|
||
|
|
HREF="node201.html">Index</A></B>
|
||
|
|
<!--End of Navigation Panel-->
|
||
|
|
<ADDRESS>
|
||
|
|
Miller Puckette
|
||
|
|
2006-12-30
|
||
|
|
</ADDRESS>
|
||
|
|
</BODY>
|
||
|
|
</HTML>
|