MIDI Communications

Platform independent realtime MIDI input and output for Ruby.

This library is part of a suite of Ruby libraries for MIDI:

Function	Library
MIDI Events representation	MIDI Events
MIDI Data parsing	MIDI Parser
MIDI communication with Instruments and Control Surfaces	MIDI Communications
Low level MIDI interface to MacOS	MIDI Communications MacOS Layer
Low level MIDI interface to Linux	TO DO (by now MIDI Communications uses alsa-rawmidi)
Low level MIDI interface to JRuby	TO DO (by now MIDI Communications uses midi-jruby)
Low level MIDI interface to Windows	TO DO (by now MIDI Communications uses midi-winm)

This library is based on Ari Russo's library UniMIDI.

Features

Supports OSX, Linux, JRuby, Windows and Cygwin
No compilation required
Both input and output to and from multiple devices concurrently
Generalized handling of different MIDI and SysEx Message types
On OSX use IAC to internally route MIDI to other programs
No events history and no buffers optimization

Requirements

MIDI Communications uses one of the following libraries, depending on which platform you're using it on. The necessary library should install automatically with the midi-communications gem.

Platform

OSX: midi-communications-macos
JRuby: midi-jruby (TODO: update to midi-communications-jruby)
Linux: alsa-rawmidi (TODO: update to midi-communications-linux)
Windows/Cygwin: midi-winmm (TODO: update to midi-communications-windows)

Install

If you're using Bundler, add this line to your application's Gemfile:

gem "midi-communications"

Otherwise...

gem install midi-communications

Usage

Some examples are included with the library:

Tests

MIDI Communications includes a set of tests which assume that an output is connected to an input. You will be asked to select which input and output as the test is run.

The tests can be run using:

rake test

See below for additional notes on testing with JRuby.

Documentation

rdoc (TODO)

Platform Specific Notes

JRuby

(TO CONFIRM) You must be in 1.9 mode. This is normally accomplished by passing --1.9 to JRuby at the command line. For testing in 1.9 mode, use jruby --1.9 -S rake test
(TO CONFIRM) javax.sound has some documented issues with SysEx messages in some versions OSX Snow Leopard which do affect this library.

Linux

(TO CONFIRM) libasound and libasound-dev packages are required

Differences between MIDI Communications library and UniMIDI library

MIDI Communications is mostly a clone of UniMIDI with some modifications:

Uses MIDI Communications MacOS Layer instead of ffi-coremidi
Removed buffering (to reduce CPU usage in some scenarios)
Source updated to Ruby 2.7 code conventions (method keyword parameters instead of options = {}, hash keys as 'key:' instead of ':key =>', etc.)
Updated dependencies versions
Renamed module to MIDICommunications instead of UniMIDI
Renamed gem to midi-communications instead of unimidi
TODO: update tests to use rspec instead of rake
TODO: migrate to (or confirm it's working ok on) Ruby 3.0 and Ruby 3.1

Then, why does exist this library if it is mostly a clone of another library?

The author has been developing since 2016 a Ruby project called Musa DSL that needs a way of representing MIDI Events and a way of communicating with MIDI Instruments and MIDI Control Surfaces.

Ari Russo has done a great job creating several interdependent Ruby libraries that allow MIDI Events representation (MIDI Message and Nibbler) and communication with MIDI Instruments and MIDI Control Surfaces (unimidi, ffi-coremidi and others) that, with some modifications, I've been using in MusaDSL.

After thinking about the best approach to publish MusaDSL I've decided to publish my own renamed versions of the modified dependencies because:

The original libraries have features (buffering, very detailed logging and processing history information, not locking behaviour when waiting input midi messages) that are not needed in MusaDSL and, in fact, can degrade the performance on some use cases in MusaDSL.
The requirements for Musa DSL users probably will evolve in time, so it will be easier to maintain an independent source code base.
Some differences on the approach of the modifications vs the original library doesn't allow to merge the modifications on the original libraries.
Then the renaming of the libraries is needed to avoid confusing existent users of the original libraries.
Due to some of the interdependencies of Ari Russo libraries, the modification and renaming on some of the low level libraries (ffi-coremidi, etc.) forces to modify and rename unimidi library.

All in all I have decided to publish a suite of libraries optimized for MusaDSL use case that also can be used by other people in their projects.

Function	Library	Based on Ari Russo's	Difference
MIDI Events representation	MIDI Events	MIDI Message	removed parsing, small improvements
MIDI Data parsing	MIDI Parser	Nibbler	removed process history information, minor optimizations
MIDI communication with Instruments and Control Surfaces	MIDI Communications	unimidi	use of MIDI Communications MacOS Layer
Low level MIDI interface to MacOS	MIDI Communications MacOS Layer	ffi-coremidi	removed buffering and process history information, locking behaviour when waiting midi events, improved midi devices name detection, minor optimizations
Low level MIDI interface to Linux	TO DO
Low level MIDI interface to JRuby	TO DO
Low level MIDI interface to Windows	TO DO

Author

Javier Sánchez Yeste

Acknowledgements

Thanks to Ari Russo for his ruby library unimidi licensed under Apache License 2.0.