Generating a PD Plugin-Wrapper Abstraction

The test patch of Fig.K.8 was constructed in pd by manually attaching user-interface elements to the left (control) inlet of the plugin. As is well described in [31], one can alternatively use the faust2pd script to generate a pd abstraction containing the plugin and its pd controllers. When this abstraction is loaded into pd, its controllers are brought out to the top level using the ``graph on parent'' mechanism in pd, as shown in Fig.K.10.

The faust2pd script works from the XML file generated by Faust using the -xml option:

  > faust -xml -a puredata.cpp -o cpgrui-pd.cpp cpgrui.dsp
  > faust2pd cpgrui.dsp.xml

Adding the -xml option results in generation of the file cpgrui.dsp.xml which is then used by faust2pd to generate cpgrui.pd. Type faust2pd -h (and read [31]) to learn more of the features and options of the faust2pd script.

The generated abstraction can be opened in pd as follows:

  > pd cpgrui.pd

Figure K.9 shows the result. As indicated by the inlet~ and outlet~ objects, the abstraction is designed to be used in place of the plugin. For this reason, we will refer to it henceforth as a plugin wrapper.

Notice in Fig.K.9 that a plugin wrapper forwards its control messages (left-inlet messages) to the encapsulated plugin, as we would expect. However, it also forwards a copy of each control message to its control outlet. This convention facilitates making cascade chains of plugin-wrappers, as illustrated in faust2pd examples such as synth.pd.^K.12

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.