MIDI channel filter in standalone plugin host

Audio Plugins
1

Is there a way to filter out MIDI Channels when using the AudioProcessorPlayer in a way that the plugin only receives messages from MIDI Channel 1 for example?

It’s a common request by iOS users to filter out MIDI channels. This way they can control different instruments with the same MIDI device.

Any ideas welcome.

2

Would it work to override AudioProcessorPlayer::handleIncomingMidiMessage and use it to filter by midi channel?

3

Thanks. I will try that.

It already feels like i overwrote the whole juce framework for this standalone app :slight_smile:

4

I looked at the actual code today, and it looks workable, if you subclass AudioProcessorPlayer and override handleIncomingMidiMessage like this:

void handleIncomingMidiMessage (MidiInput*, const MidiMessage& message) override
{
	if (message.isForChannel (1))
		getMidiMessageCollector().addMessageToQueue (message);
}

Presumably you’d replace the hardcoded “1” with a class member that held the MIDI channel you were screening for.

5

This may not be applicable to your use case, but I’m working on a multi-MidiChannel arpeggiator/plugin host, and what I do (simplified explanation) is take the incoming MIDI buffer, iterate through it and copy messages for a particular MidiChannel to a copyBuffer, then replace the incoming MIDI buffer with my copy and continue:

            for (const MidiMessageMetadata meta : midiMessages)
            {
                const auto msg = meta.getMessage();
                
                if (msg.isForChannel (midiChannel))
                    copyBuffer.addEvent (msg, meta.samplePosition);
            }
            // replace the incoming MIDI buffer with a copy of this one
            // that only has a certain MIDI channel for passing down the chain
            midiMessages = copyBuffer;
1 Like
6

Thanks for the additional code. I endet up with something like this:

void handleIncomingMidiMessage (MidiInput * midiInput, const MidiMessage &message) override
{
    if (message.isForChannel (midiChannel))
    {
        AudioProcessorPlayer::handleIncomingMidiMessage(midiInput, message);
    }
}
1 Like
7

Oh, right, calling the base class method (instead of re-creating it, as I did) is probably easier and more future-proof.