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

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.

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.

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.

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