[BUG] Juce 5.4.7 AudioPluginHost: MIDI VST3's have incorrectly echoed input notes

[stephenk]

Now that JUCE AudioPluginHost has a MIDI Output, it’s worth pointing out that a bug still exists in the VST3 handling code, as discussed here:

AudioPluginHost 5.4.3 : MIDI effect produces double notes?

(didn’t find any existing topic, so here goes) I think I’m trying to do something simple, and it almost works. I’ve created a simple MIDI effect “Transpose”. I tried using the AudioPluginHost to test it. MIDI input (internal) => MIDI effect “Transpose” => Synth plugin (image hopefully attached) The odd thing is that when Transpose is changed, the Synth plays both the original notes and the transposed ones. As if the Synth is always listening to the internal MIDI input, and the effect is just…

When you make a MIDI Processing Plugin, with VST2 the input notes are not automatically added to the output; when you make a VST3, they are (wrong).

In other words, with the ArpeggiatorDemo, you play input notes and it takes them and arpeggiates them to the output. In a VST2, that’s all you get at the output (correct). With a VST3, you get the input notes at the output added on top of the arpeggiated notes.

Putting in the following line and recompiling the AudioPluginHost fixes the issue:

in juce_VST3PluginFormat.cpp:

    template <typename FloatType>
    void processAudio (AudioBuffer<FloatType>& buffer, MidiBuffer& midiMessages,
                       Vst::SymbolicSampleSizes sampleSize, bool isProcessBlockBypassedCall)
    {
// …
    processor->process (data);
// ...
    midiMessages.clear(); // <== **REQUIRED TO ADD THIS**
    MidiEventList::toMidiBuffer (midiMessages, *midiOutputs);
// …
}

JUCE team: if you need an example for this, let me know.

[reuk]

Thanks for the bug report, the issue is fixed on the juce6 branch:

VST3: Fix duplicate messages in VST3 wrapper

[pflugshaupt]

Uh… does that mean there won’t be any bugfixes on the Juce 5 branches anymore? Cherry-picking from the Juce6 branch seems problematic without having a juce6 license.

[reuk]

I’ll be cherry-picking this one into JUCE 5. Other bugfixes will happen on a case-by-case basis.

[pflugshaupt]

Thank you. I understand it makes no sense for more complex fixes that might not be possible to just merge, but as long as we can’t buy Juce 6 and it is in beta, it would be great to get those small fixes.