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<chapter id="SignalFlowGraphOpcodes">
<title>Signal Flow Graph Opcodes</title>
<para>
These opcodes enable the use of signal flow graphs
(AKA asynchronous data flow graphs) in Csound orchestras.
Signals flow from the outlets of source instruments
and are summed in the inlets of sink instruments.
Signals may be krate, arate, or frate.
Any number of outlets may be connected to any number of inlets.
When a new instance of an instrument is instantiated during performance,
the declared connections also are automatically instantiated.
</para>
<para>
Signal flow graphs simplify the construction of complex mixers,
signal processing chains, and the like. They also simplify the re-use
of "plug and play" instrument definitions and even entire sub-orchestras,
which can simply be #included and then "plugged in" to existing orchestras.
</para>
<para>
Note that inlets and outlets are defined in instruments without reference
to how they are connected. Connections are defined in the orchestra header.
It is this separation that enables plug-in instruments.
</para>
<para>
Inlets must be named. Instruments may be named or numbered, but in
either case each source instrument must be defined
in the orchestra before any of its sinks. Naming instruments makes
it easier to connect outlets and inlets in any higher-level orchestra
to inlets and outlets in any lower-level #included orchestra.
</para>
<para>
The signal flow graph opcodes include:
<link linkend="outleta"><citetitle>outleta</citetitle></link>, for
sending an arate signal from any instrument out a named port.
<link linkend="outletk"><citetitle>outletk</citetitle></link>, for
sending a krate signal from any instrument out a named port.
<link linkend="outletf"><citetitle>outletf</citetitle></link>, for
sending an frate signal from any instrument out a named port.
<link linkend="inleta"><citetitle>inleta</citetitle></link>, for
receiving an arate signal through a named port.
<link linkend="inletk"><citetitle>inletk</citetitle></link>, for
receiving a krate signal through a named port.
<link linkend="inletf"><citetitle>inletf</citetitle></link>, for
receiving an frate signal through a named port.
<link linkend="connect"><citetitle>connect</citetitle></link>, for
routing the signal from a named outlet in a source instrument
to a named inlet in a sink instrument.
<link linkend="alwayson"><citetitle>alwayson</citetitle></link> for
permanently activating an instrument from the orchestra header,
without need of a score statement, e.g. for use as an effect processor
receiving inputs from a number of sources.
<link linkend="ftgenonce"><citetitle>ftgenonce</citetitle></link> for
instantiating function tables from within instrument definitions, without
need for f-statements in the score or ftgen opcodes in the orchestra header.
</para>
<para>
A typical scenario for the use of these opcodes would be something like this.
A set of instruments would be defined, each in its own orchestra file, and
each instrument would define inlet ports, outlet ports, and function tables within itself. Such
instruments are completely self-contained. Then, a set of effects processors, such
as equalizers, reverbs, compressors, and so on, would also be defined, each in its
own file. Then, a customized master orchestra would #include the instruments
and effects to be used, route the outputs of some instruments into one equalizer
and the outputs of other effects into another equalizer, then route the outputs of
both equalizers into a reverb, the output of the reverb into a compressor, and
the output of the compressor into a stereo output soundfile.
</para>
<refsect1>
<!--To add examples, create the csd file in the examples directory, then run:-->
<!--python csd2docbook.py -f newopcodename.csd-->
<!--to generate the xml highlighted version used below-->
<title>Example</title>
<para>
Here is an example of the signal flow graph opcodes. It uses the file <ulink url="examples/signalflowgraph.csd"><citetitle>signalflowgraph.csd</citetitle></ulink>.
<example>
<title>Example of the signal flow graph opcodes.</title>
<xi:include href="examples-xml/signalflowgraph.csd.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
</example>
</para>
</refsect1>
</chapter>
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