Android Koala crashes when a MIDI controller and a physical keyboard are connected

[gstepniewski]

I've been working on creating a MIDI mapping for my Launchpad recently and have experienced a large amount of crashes. They seem to mostly occur when plugging/unplugging a controller, but happened also while assigning CCs to things and just playing around.

Is there a way for me to generate stacktraces/dumps/whatever to make it easier to debug? Or do they get logged somewhere automatically (like Firebase) anyway? I'm happy to try reproducing them if that helps debugging/fixing/testing.

[mazbox]

Hi Greg

Thanks for the bug report - what would be awesome is if you could give me (1) the make/model of phone + OS version, and (2) some steps to reproduce and an idea of how frequently its replicable with the reproducing steps.

I can't seem to reproduce this - I do get crash reports but they're not as useful as reproduction steps as a lot of the native (e.g. ndk) stack can get garbled, and its nice to be able to recreate exactly then problem in a test case so it doesn't happen again.

[gstepniewski]

I have been able to figure out full reproduction steps of the issue. My phone is Pixel 5 with Android 13 and I have two MIDI controllers that I'm using - Novation Launchpad X and Akai MPK Mini Mk3.

The MPK works perfectly when connected to the phone on its own, I can disconnect it or connect it multiple times and at any point while running the app. But when I connect the Launchpad X after having started Koala, the first time I hit a pad on the controller Koala instantly crashes with a segfault:

libc com.elf.koalasampler A Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x7500000000 in tid 19149 (Thread-42), pid 18963 (lf.koalasampler)

No other useful information is printed to LogCat. Note that despite what I wrote in the original description this has nothing to do with MIDI mapping, it doesn't even have to be active for this to happen. I just noticed the crashes while I was working on my Launchpad configuration (because I was constantly switching between the computer to upload a new config and the phone to test it out).

One important thing is that when the Launchpad X is disconnected or connected while Koala is running, the app will restart itself (go back to the loading screen and then to the pads, and if a sequence was playing it gets stopped).

It seems that this is related to the fact that besides being a MIDI controller, the Launchpad is also a HID device (this was added with an update some time ago, and since then you can map pads to send keystrokes). I have been able to reproduce it using a separate MIDI controller (MPK Mini) and an actual keyboard (Logitech K380 over Bluetooth):

1. Start Koala
2. Connect MPK Mini
3. Connect K380 keyboard (the app restarts itself now, just as it does with the Launchpad!)
4. Hit Z on the keyboard and the bottom left pad plays properly (this step is optional, just mentioning that the keyboard itself works fine)
5. Hit a pad or key on the MPK Mini -> the app crashes

The app also crashes if steps 2 and 3 are reversed, i.e. connect the K380 keyboard first (the app restarts) and then connect the MPK Mini (the app doesn't restart but still crashes as soon as I send a MIDI message). And just like in the original scenario, the keyboard can play the pads at any stage just fine.

I hope this helps track it down, but let me know if you need any more details or any further testing done!

[mazbox]

Thanks a lot for the feedback!

If you take the bluetooth keyboard out of the equation does it still happen? i.e.:

1. Open Koala
2. Plug in MPK Mini
3. Hit a pad

It would be interesting to know if its the introduction of the bluetooth keyboard that's causing problems?

I tried recreating just plugging in a launchpad after starting koala on a Pixel 3a and worked as expected. I don't have a bluetooth keyboard for testing at the moment.

[gstepniewski]

It only seems to happen when a keyboard becomes involved - either bluetooth or wired. In fact, a wired keyboard connected while the app is running crashes it immediately before I even reach out for the MIDI controller.

I did some testing on some other phones I had around:

• Samsung Galaxy S9, Android 10
• Samsung Galaxy A20E, Android 11
• Samsung Galaxy S10E, Android 12

The crash happened on all three exactly as it does on the Pixel (I could only test with the bluetooth keyboard because they don't seem to support usb-c hubs and wouldn't turn the mpk mini on).

Which Launchpad do you have and which software version does it have? Apparently only the Mini Mk3 and X upgraded to newest firmware support keystrokes and would therefore identify as a HID device as well as MIDI - which means if you have a different one you won't be able to reproduce the crash.