Processing MIDI signals in JUCE

Yuki Sato

I would like to create an original MIDI synth from this repository.

However, it seems that the input MIDI data is not received by the program and no sound is played.

It seems to add a program about MIDI processing in the processBlock function part, but I don't understand.

The program is currently as follows.

void CustomAudioProcessor::processBlock(juce::AudioBuffer<float>& buffer, juce::MidiBuffer& midiMessages)
{
    auto samples = static_cast<RNBO::Index>(buffer.getNumSamples());
   
    //auto tc = preProcess(midiMessages);
    _rnboObject.process(
                        buffer.getArrayOfReadPointers(), static_cast<RNBO::Index>         (buffer.getNumChannels()),
                        buffer.getArrayOfWritePointers(), static_cast<RNBO::Index>(buffer.getNumChannels()),
			  samples,
			  &_midiInput, &_midiOutput
			  );
     DBG("_midiInput size: " << _midiInput.size());
     //postProcess(tc, midiMessages);
}

As for preProcess and postProcess, they are private members and cannot be used without changing them to public members.

Please let me know if there is any way.

Alex Norman

The main processing unit in our adapter derives from juce::AudioProcessor. That class handles midi i/o in its processBlock method via that midiMessages parameter. If you're not getting MIDI in and out that you expect, I suspect you aren't getting the MIDI to/from JUCE that you expect and maybe there is a JUCE forum to ask about that.

Maybe you can give us some more information, how are you sending MIDI to your AudioProcessor?

Yuki Sato

Thank you for your reply Alex.

I simply copied and pasted the part of the processBlock method you provided (RNBO_JuceAudioProcessor.cpp) inside CustomAudioProcessor.cpp here.

I tried the normal audio effectors, where the audio signals were input and processed without any problems.

When I logged the received MIDI message as follows

void CustomAudioProcessor::processBlock(juce::AudioBuffer<float>& buffer, juce::MidiBuffer& midiMessages)
{
   for (const auto meta : midiMessages)
   {
       auto message = juce::MidiMessage(meta.data, (int)meta.numBytes);

       if (message.isNoteOn())
       {
           DBG("Note On: " << message.getNoteNumber() << " Velocity: " << message.getVelocity());
       }
   }

   auto samples = static_cast<RNBO::Index>(buffer.getNumSamples());
   _rnboObject.process(
                        buffer.getArrayOfReadPointers(), static_cast<RNBO::Index>(buffer.getNumChannels()),
                        buffer.getArrayOfWritePointers(), static_cast<RNBO::Index>(buffer.getNumChannels()),
			  samples,
			  &_midiInput, &_midiOutput
			  );
   DBG("_midiInput size: " << _midiInput.size());

}

in processBlock, I was able to get the value, but when I logged _midiInput.size(), the value was zero.

It seems that the received midi signals are not being sent inside the RNBO object I created.

In rnbo~, the structure is simple: a notein object is placed at the head and from there it is assigned to the oscillator frequency across the mtof.

Do I need to add any other special treatment?

JBG

I mean, your example is pretty straightforward, no?

You receive any midi input in juce::MidiBuffer& midiMessages
You have two functions preProcess and postProcess that (I assume) moves the midi input to/from member variables _midiInput and _midiOutput
You pass member variables variables _midiInput and _midiOutput to your _rnboObject

If you comment out preProcess and postProcess, your _rnboObject is never interacting with the incoming midi input. From what you describe it's difficult to get the full context of your use case, but if you're unable to use preProcess and postProcess directly, you'll have to write your own functions to move the midi data to/from _midiInput and _midiOutput

Yuki Sato

Thank you for your reply JBG.

As you say, what I want to do is simple and ultimately pass member variables variables _midiInput and _midiOutput to my _rnboObject.

As for preProcess and postProcess, when they are used, they are declared as private members in RNBO_JuceAudioProcessor.h, where they are declared, so they cannot be used in CustomAudioProcessor.cpp without modification.

So I changed these to protected members and built, but in the end there was no sound.

I don't know how to deal with these because of my limited knowledge of C++.

Finally resolved. Thank you. 3/12