4.7.1 sfplugin

sfplugin is the universal executable. Any network of Marsystems stored as a plugin can be loaded at run-time and sound can flow through the network. The following example with appropriate plugins will peform playback of foo.wav and playback with real time music speech classification of foo.wav.

     sfplugin -p plugins/playback.mpl foo.wav
     sfplugin -p musp_classify.mpl foo.wav

Writing a basic sfplugin plugin

The sfplugin application expects that certain controls are available in any network it tries to handle. Therefore, one of the simplest demonstration plugins one can write is a plugin containing a SoundFileSource and an AudioSink, demonstrated below. As the sfplugin does not know were the sources and sinks are in the network it is necessary to link the composite's controls with appropriate controls in the network.

     // create the network that will become the plugin
     MarSystem* sys = mng.create( "Series", "head" );
     
     // create the two required MarSystems
     sys->addMarSystem( mng.create( "SoundFileSource", "src" ) );
     sys->addMarSystem( mng.create( "AudioSink", "dest" ) );
     
     // while we don't actually want to play a file now, supply a valid
     // filler name to keep the program happy; sfplugin will update it later
     sys->updctrl( "SoundFileSource/src/mrs_string/filename",
     	      "../../SuperGroovyLateralGeniculateNucleus.au" );
     
     // since we're not playing the song now, set initAudio to false;
     // sfplugin will update this to true when the network is executed there
     sys->updctrl( "AudioSink/dest/mrs_bool/initAudio", false );
     
     // set those pesky control links!
     sys->linkctrl( "mrs_string/filename", "SoundFileSource/src/mrs_string/filename" );
     sys->linkctrl( "mrs_bool/initAudio" , "AudioSink/dest/mrs_bool/initAudio" );
     sys->linkctrl( "mrs_natural/pos"    , "SoundFileSource/src/mrs_natural/pos" );
     sys->linkctrl( "mrs_bool/hasData"  , "SoundFileSource/src/mrs_bool/hasData" );
     
     // finally, write the network to a file; the plugin can be run as
     // follows: sfplugin -p some_plugin.mpl ../../SamsSavorySuperiorColliculus.au
     ofstream ofs( "some_plugin.mpl" );
     ofs << (*sys) << endl;