mt32-pi

A Buildroot external tree which which turns your Raspberry Pi 2 into a dedicated Roland MT-32 emulator based on MUNT/libmt32em.

The aim is to have the Raspberry Pi boot into a working state in about 5 seconds.

How to use it

• Check out this repo.

• Copy MT32_CONTROL.ROM and MT32_PCM.ROM to the mt32-roms folder (you need to source these copyrighted ROMs yourself).

• Download and extract Buildroot 2016.11 or later.

• Build the system (this will take a long time):

  cd /path/to/buildroot
  make BR2_EXTERNAL=/path/to/this/repo raspberrypi2_defconfig
  make
  

• After a successful build, an SD card image is located in output/images/sdcard.img.

• Copy the image onto an SD card with dd (use the correct argument for the device representing your SD card reader):

  sudo dd if=output/images/sdcard.img of=/dev/sdc bs=1M
  sync
  

• Place the SD card into the Raspberry Pi 2, attach a USB MIDI cable, and enjoy!

TODO

• There is some kind of delay in the handling of MIDI messages when many messages arrive at once (more complex songs). Need to figure out what this is being caused by (slow Pi USB MIDI? Would a GPIO MIDI interface be better? Threading problem with mt32d?).
• Hardcoded to use (poor) internal sound and first USB MIDI device. Need to script hotplugging things properly and select appropriate devices.
• Maybe try to use PREEMPT_RT kernel patch to see if it helps to get the latency of mt32d down as low as possible with various audio devices. N.B.: USB audio devices can achieve lower latency and superior sound quality to the internal audio.
• Provide configurations for external LCD screens such as 3.2" touchscreens and various character displays in order to allow the virtual MT-32 to output messages and be controlled.
• Reduce initial build time and image size by disabling unnecessary kernel modules.
• In relation to above, reduce startup time. There's a 2 second sleep while we wait for the MIDI interfaces to come up before invoking aconnect; this needs to go away. A 'release' build could also remove network/SSH as this increases startup time.