Use a different sound font

[bmaupin]

Android's built-in Sonivox EAS MIDI sound font is pretty terrible.

Plan

• Try one of the forks of KyoSherlock/MidiDriver
  • Test and see how slow it actually is
  • Test with a bigger sound font
  • Test with a smaller sound font
• Try to create a JET file and play it back
  • Create a JET file with JET creator with a custom sound font
  • Play it back in an app and see what kind of latency it has
  • Is it properly played with the custom sound font?
  • See how difficult it would be to create a JET file programatically on the fly in an Android app...
• Try to get custom sound font working with billthefarmer/mididriver
  • This might be the next best option...
• See how simple it would be to just generate MP3s

Notes

• Use the existing Sonivox MIDI driver (https://github.com/billthefarmer/mididriver) with a different sound font
  • I'm guessing this would be non-trivial given that it hasn't been figured out yet by people who doubtless know way about it more than me: Costum soundfont is possible? billthefarmer/mididriver#21
  • On the other hand, it looks like it hasn't been attempted in ~5 years and there have been a lot of changes to the underlying Android code since then: https://android.googlesource.com/platform/external/sonivox/
• Use a JET file?
  • We could potentially generate one programatically and then play it back?
  • Documentation
    • https://developer.android.com/guide/topics/media/jet/jetcreator_manual
    • https://developer.android.com/reference/android/media/JetPlayer
• Use KyoSherlock/MidiDriver or one of its forks
  • Seems like it's just a wrapper around https://github.com/kshoji/javax.sound.midi-for-Android, which itself is a port of javax.sound.midi
  • ⚠ Since it's Java, it might be slow (Sound lagging KyoSherlock/MidiDriver#5)
  • More importantly, it's improperly licensed: Incorrect license given - should be GPLv2 KyoSherlock/MidiDriver#8 This is wrong! The "infringing" code isn't plain GPLv2, it's GPLv2 with the classpath exception (https://softwareengineering.stackexchange.com/a/326325/160348) 🎉
• Use https://github.com/kshoji/javax.sound.midi-for-Android directly
  • I don't believe this is possible since I think a synthesizer is also needed, hence KyoSherlock/MidiDriver
• Use Fluidsynth
  • Pros
    • It should Just Work™
  • Cons
    • It's a native library with a lot of dependencies and a complex build process. So we'd either need to adopt the complex build process ourselves or import the pre-built binaries, which would balloon this repository
    • The binaries themselves would probably balloon the application (the pre-built binaries are ~20 MB each, times 4 architectures)
• Generate MP3s and package them in the app
  • Pros
    • Might be the simplest approach...
  • Cons
    • Not very flexible if we ever want to add new instruments, change sound font, etc...
      • But if we could script it, maybe it would be the most straightforward approach?