How to know Apple has recieved the bug report

If you get the FB reference, that means it was received.

But it is Apple's decision to handle it or not, you have no control on the process (and note the number of FB: literally millions).
When did you send FB ?

What was the bug ?

I post it on 9/19.
The description of the bug:
Our app simulate guitar play based on midi data. With iOS14 all played sounds are broken and seems like CoreAudio failing play midi notes real time and are stuck somewhere.
The issue is quite serious for us because playing midi and simulate guitar play is the main function of out app.

Thanks

Did you inspect the incoming MIDI packets? My impression is that iOS 14 does not handle SysEx messages correctly. I have a case where a SysEx messages arrives after a Note On message, in the same packet. This does not conform to the Core MIDI specification.

I 've inspected the midi packets and noticed that iOS14 failed to handle multi channel midi stream. My app uses a few midi channels, each of them plays specific instruments such as guiter, drum, piano so on. The first one or two bars of a song just played drum and worked fine. Once the second channel came in the other channels including the second on never came in.

The previous post had some misunderstanding. Here is the correct description.

I 've inspected the midi packets and noticed that iOS14 failed to handle multi channel midi stream. My app uses a few midi channels, each of them plays specific instruments such as guiter, drum, piano so on. The first one or two bars of a song just played drum and worked fine. Once the second channel came in a lot of midi notes lost.

There are no SysEx messages involved? I have problems only with these, but no issues with multiple channels.

To be more specific: The user plays a chord on the keyboard. The keyboard adds a SysEx message after the third note, to signal it has detected a chord. The app ought to receive four packets:

1. Note On

2. Note On

3. Note On

4. SysEx (chord detection)

But it receives three packets:

1. Note On

2. Note On

3. Note On, SysEx

This is illegal, as

https://developer.apple.com/documentation/coremidi/midipacket?language=objc

says

"In the case of system-exclusive messages, a packet may only contain a single message, or portion of one, with no other MIDI events."

and my apps are not prepared to handle these malformed packets.

Your problem seems to be a different one, though.

Hi polaron.de,

Our app plays midi sequeces comes from files and the files contains no SysEx.
And your replay is valuable for me, because it implies Apple some how has touched components affecting behavior.

Thanks for your reply.

Maybe iOS 14 has the habit to merge several MIDI messages into a single packet (which is illegal for SysEx messages), and your app has a problem with parsing these packets?

Hi polaron.de,
You are right!
I've checked the lengths of packets. With iOS13 all lengths are 3. With iOS14 they are 3,6,9, so on.

Thanks a lot