Create virtual Midi Port on iPad

[Ayra]

Hi, I’d like to create a virtual midi port on my iPad to send message to some apps as Cubasis or AUM, but unfortunately with this code that woks on desktop app doesn’t work on iPad: the virtual port is not detected by any app and when I try to click a button that create a message to send to that port the app gives me the error: JUCE Message Thread (1): EXC_BAD_ACCESS (code=1, address=0x1c8).

MainComponent::MainComponent()
{
setSize (600, 400);
addAndMakeVisible(tb);
mo.reset(MidiOutput::createNewDevice(“test”));
MidiOutput::openDevice(mo->getDefaultDeviceIndex());
tb.onClick = [this] {
auto mm = MidiMessage::noteOn(1, 64, uint8(127));
mo->sendMessageNow(mm);
};
}

How can I solve the error and create a virtual midi port on my iPad?

[matkatmusic]

Consider this experience your first lesson in unsafe pointer usage

@ayra.productions

mo.reset(MidiOutput::createNewDevice(“test”));

you need to make sure before you use mo that it is not holding a nullptr.

if( mo.get() != nullptr )
{
    MidiOutput::openDevice(mo->getDefaultDeviceIndex());
    tb.onClick = [this] {
        auto mm = MidiMessage::noteOn(1, 64, uint8(127));
        mo->sendMessageNow(mm);
    };
}

Secondly, can you even confirm if Virtual Midi ports exist on iOS? I thought they were an OS-X specific thing only.

[Ayra]

Really Thank you! I suppose that virtual midi ports exist also in iOS because I noticed that when I open a synth app I could send midi message to it through a port that the synth creates at opening (for example I opened Kaspar, Igrand, iSynphonic, synthmaster one and after cubasis and from cubasis I have a list of output midi ports with the name of apps opened through I can send message from cubasis to these other apps).

[matkatmusic]

Announcing Inter-App Audio (IAA) support for standalone plug-ins in JUCE 5

Hi all, We have just released Inter-App Audio (IAA) support for standalone plug-ins on iOS as a JUCE 5 feature on the develop branch. To make your standalone plug-in available as an IAA instrument or effect you need to compile the most recent version of the Projucer. The new Projucer provides a new plug-in configuration option, “Enable Inter-App Audio”, which does what you would expect. In many cases you will also want to enable “Microphone access” in the iOS Xcode build options. There is a…

[Ayra]

I tried again creating new project, this time choosing audio plugin from wizard in Projucer enabling in setting only standalone and IAA, after I created a new midi output device and a new midi input device but nothing change. Here what I’ve done:
on Plugin Editor I put under private members those two variables:

MidiInput* mi;
MidiOutput* mo;

on init function I put this code:

mo = MidiOutput::createNewDevice("MyDeviceOut");
// PREVIOUS LINE PRINT IN CONSOLE: CoreMIDI error: 417 - ffffd5a4
if (mo != nullptr) {
    MidiOutput::openDevice(mo->getDefaultDeviceIndex());
}

mi = MidiInput::createNewDevice("MyDeviceIn", this);
// PREVIOUS LINE PRINT IN CONSOLE; CoreMIDI error: 560 - ffffd5a4
if (mi != nullptr) {
    mi->start();
}

Obviously I tried that code on a desktop version and it works!
In attachment a screenshot of how cubasis looks when before it I open another app that create his own midi ports (while if I launch my test it looks the same but without in this case “iGrand Piano”).

Some Ideas? (really thank you again for support!).

[ed95]

Have you enabled the “Audio Background Capability” setting in the iOS exporter in the Projucer? This is needed to create MIDI devices otherwise CoreMidi will throw a kMIDINotPermitted error (which is the ffffd5a4 error you’re seeing).

[ed95]

Actually, we could do a much better job of making this clearer so things won’t just silently fail like in your case. I’ll push something shortly.

EDIT:

iOS: Made it clear that the "Audio Background Capability" setting must be enabled for MidiInput/Output::createNewDevice() to succeed

[Ayra]

Really thank you, now all works perfectly!

[gustav-scholda]

Is this actually working?
Here we can only successfully call MidiInput::createNewDevice() if the app is running standalone. If we run the AUv3 in AUM or Cubasis we get the kMIDINotPermitted error.

We are using CMake and we are setting BACKGROUND_AUDIO_ENABLED
to TRUE which results in the same XCode Project Config as if we were using the Projucer. However even within XCode it seems I can’t set the Background Mode for Audio like stated in Apple’s documentation here:

Configuring your app for media playback | Apple Developer Documentation

There are apps around which create their own virtual Midi ports though, even when hosted as an AUv3. So there must be a way, but how?

Thank you!

[gustav-scholda]

Nobody here using virtual Midi Ports on iOS? It’s pretty common…

[gustav-scholda]

Ok, I’ve spent a couple of hours down the rabbit hole:

It seems like this never worked for AUv3s, @Ayra also told me in a PM that it was only tested in Standalone. There seems to be no way to enable Audio Background Mode for an AUv3, I’ve pretty much tried everything in XCode…

It’s not a JUCE bug at least, it seems to be a restriction by Apple. Maybe one of the JUCE devs, @reuk ?, can confirm this and add it to the documentation? My hours are gone but someone else’s could be saved

[QuilioLtd]

Are there no AUv3s that can handle this functionality?

[gustav-scholda]

You can‘t create your own virtual MIDI devices but you can enable MIDI I/O:

AUv3 iOS and enabling MIDI input ports

To select the use of kAudioUnitType_MusicEffect you can set the AU_MAIN_TYPE definition, I have done this in CMake in the juce_add_plugin section. juce_add_plugin("Target" AU_MAIN_TYPE kAudioUnitType_MusicEffect all the other flags.....)