Sorry for the delay, I’ve been trying to get a consistent repro, but I’m afraid I haven’t succeeded yet. The issue happens more frequently in our app, but I got the MidiDemo to reproduce it a few times now by sending lots and lots of note-ons by tapping the keyboard rapidly.
Since updating to the official iOS 14.2 release (using an iPad 8, OSX 10.15.7 and xcode 12.1, but having downloaded the 14.2 sdk with xcode 12.2 beta), we are seeing two issues and are assuming they are different manifestations of the same underlying problem.
The first is a crash when JUCE calls MIDISend (an CoreMIDI call):
and the second is a series of 3 errors output to the debug log when JUCE calls MIDIObjectGetString/IntegerProperty(), when attempting to get properties about the device in either MidiInput::getAvailableDevices() or MidiOutput::getAvailableDevices():
Here are the printed error messages:
CoreMIDI error: 56 - ffffffce
CoreMIDI error: 62 - ffffffce
CoreMIDI error: 70 - ffffffce
Using https://osstatus.com/ (and this forum post: How to translate CoreMIDI error numbers?) we’ve found that ffffffce corresponds to a kAudio_ParamError from CoreAudio.
Both issues happen after we have connected to a physical midi BT device and have been communicating with it – although it can happen almost immediately or after a few minutes.
We assume the first issue (MIDISend()) happens if the error occurs while we are already on the path to send midi, and the second (getAvailableDevices()) when our code detects the device has gone away, so stops sending midi, but continues to poll the device list.
Although anecdotal, a quick googling of “ios 14.2 midi issue” does reveal a few products are also facing this issue: