Core Midi sending wrong usb packets on MacOS 13.3.1

Question

I've got an app that communicates with midi devices, this app worked fine for years, however since MacOS 13.3 and iOS 16 users complained about strange behaviors.

After days of debugging I found out that the USB Midi Packets sent are sometimes invalid (wrapped in sysex headers).

Here is the extract used to sent a single midi message

  UInt8 mBuffers[100];
  MIDIPacketList* packetList = (MIDIPacketList*) mBuffers;
  MIDIPacket* packet = MIDIPacketListInit(packetList);
    MIDIPacketListAdd(packetList, sizeof(mBuffers), packet, 0, messageLength, (Byte *) messageData);
    
  printf("Sending %i bytes ", messageLength);
  for (int i = 0; i &lt; messageLength; i++)
  {
      if (i > 0) printf(":");
      printf("%02X", (Byte)messageData[i]);
  }
  printf("\n");
  fflush(stdout);
  
  status = MIDISend(outputPortReference, endPointReference, packetList);

Here is the output of the program when the issues occurs:

Sending 3 bytes E0:00:00
Sending 3 bytes D0:00:00
Sending 3 bytes E1:00:00
Sending 3 bytes D0:1B:00
Sending 3 bytes E2:00:00
Sending 3 bytes D0:2B:00
Sending 3 bytes E3:00:00
Sending 3 bytes D0:3B:00
Sending 3 bytes D0:4A:00
Sending 3 bytes D0:5A:00
Sending 3 bytes D0:6A:00
Sending 3 bytes D0:79:00

The data rate is relatively high (~100ms per message)

However when looking at the usb stack, the following data gets sent:

0e e0 00 00 -> Match
0d d0 00 00 -> Match
04 00 e1 00 -> WRONG  - wrapped in Sysex
04 00 d0 1b -> WRONG  - wrapped in Sysex
0f 00 00 00 -> Padding
0e e2 00 00 -> Match
0d d0 2b 00 -> Match
04 00 e3 00 -> WRONG  - wrapped in Sysex
04 00 d0 3b -> WRONG  - wrapped in Sysex
04 00 d0 4a -> WRONG  - wrapped in Sysex
0f 00 00 00 -> Padding
0d d0 5a 00 -> Match
0f 00 00 00 -> Padding
0d d0 6a 00 -> Match
04 00 d0 79 -> WRONG  - wrapped in Sysex
0f 00 00 00 -> Padding

I can't explain anymore why this is happening and looking for some advice. Since I can't debug on that level on iOS I can only guess that the root cause is the same.

Does anyone know about such an issue? Any ideas how to further debug?

951

Posted by

davidgiga1993

Reply

Then you will most likely need to update your applications if Apple has addressed issues in the API.

—
MobileTen
What do you mean? The api is still available and the behavior shouldn't change between MacOS versions. Especially since it produces invalid packets.

—
davidgiga1993
Creating a feedback ticket with a sample app and the observations above might be best.

—
MobileTen

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Answer 1

Creating a feedback ticket with a sample app and the observations above might be best.

Posted by

MobileTen

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Answer 2

For anyone interested: The behavior on MacOS and iOS is slightly different, yet both cases are annoying. I managed to resolve the MacOS issue by using the MIDI2.0 api, and sending sysex using the dedicated sendSysex method. Important: Block sending any other requests until the sysex callback has been received.

On iOS however, midi seems generally broken, regardless of which API is used:

When sysex is sent (using sendsysex) all midi messages after that for the next 500ms are simply dropped and not delivered.
Sending sysex directly with a MIDI 2.0 UMP packet doesn't do anything at all.

As far as I can tell there is no workaround to quickly send sysex and note/cc events, which makes my entire platform broken in the apple ecosystem.

Posted by

davidgiga1993

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Answer 3

Submitted ticket with more details: https://feedbackassistant.apple.com/feedback/12194198

Posted by

davidgiga1993

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Core Midi sending wrong usb packets on MacOS 13.3.1

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