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Notes from the desk of Shane Dunne, software development consultant

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overview [2017/08/30 16:25]
shane [The SynthSound object and class juce::SynthesiserSound] 		overview [2017/08/30 16:43] (current)
shane [The SynthSound object and class juce::SynthesiserSound]
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 The processor needs to be able to notify the GUI editor when it changes one or more synth parameters (e.g. when a new preset is selected), so it can update the GUI display. This can be done in any number of ways, but I chose to have the //VanillaJuceAudioProcessor// class also derive from the //juce::ChangeBroadcaster//, and the //VanillaJuceAudioProcessorEditor// inherit from //juce::ChangeListener//. The processor calls its //sendChangeMessage()// function to notify the editor, which results in a call to the editor's //changeListenerCallback()// function. The processor needs to be able to notify the GUI editor when it changes one or more synth parameters (e.g. when a new preset is selected), so it can update the GUI display. This can be done in any number of ways, but I chose to have the //VanillaJuceAudioProcessor// class also derive from the //juce::ChangeBroadcaster//, and the //VanillaJuceAudioProcessorEditor// inherit from //juce::ChangeListener//. The processor calls its //sendChangeMessage()// function to notify the editor, which results in a call to the editor's //changeListenerCallback()// function.
 +
 +To understand how parameter changes are propagated in the reverse direction---from GUI to synthesizer---we need the following overview some of the objects which make up the DSP aspect of VanillaJuce.
  
 ===== The "Synth" objects ===== ===== The "Synth" objects =====
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 Member variable //synth// object is a reference to the //Synth// object (which never changes). Member variable //synth// object is a reference to the //Synth// object (which never changes).
 //pParams// is a pointer to the currently-selected preset. I've made //pParams// public so the //VanillaJuceAudioProcessor// object (which creates and "owns" the one //SynthSound// object) can change it whenever a different preset is selected, so it points to the appropriate entry in the //programBank// array. //pParams// is a pointer to the currently-selected preset. I've made //pParams// public so the //VanillaJuceAudioProcessor// object (which creates and "owns" the one //SynthSound// object) can change it whenever a different preset is selected, so it points to the appropriate entry in the //programBank// array.
 +
 +All the //Gui...// class constructors take a //SynthSound*// argument, so they can use the //pParams// member to access the current parameter values, in order to display and modify them. Furthermore, whenever any part of the GUI changes a parameter value, it calls the //parameterChanged()// function, which is just this:
 +<code cpp>
 +void SynthSound::parameterChanged()
 +{
 +    synth.soundParameterChanged();
 +}
 +</code>
 +//Synth::soundParameterChanged()// simply iterates over all active (currently-sounding) voices, and calls their //soundParameterChanged()// function. (I looked at the code for //juce::Synthesiser// to see how it handles iterating over all voices.)
 +<code cpp>
 +void Synth::soundParameterChanged()
 +{
 +    // Some sound parameter has been changed. Notify all active voices.
 +    const ScopedLock sl(lock);
 +
 +    for (int i = 0; i < voices.size(); ++i)
 +    {
 +        SynthVoice* const voice = dynamic_cast<SynthVoice*>(voices.getUnchecked(i));
 +        if (voice->isVoiceActive())
 +            voice->soundParameterChanged();
 +    }
 +}
 +</code>
 +The code for //SynthVoice::soundParameterChanged()// is not so trivial, but all it really does is re-initialize the currently sounding note so that the sound changes to reflect whatever was changed in the GUI.
 +
overview.1504110337.txt.gz ยท Last modified: 2017/08/30 16:25 by shane

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