portmidi

Want to output to an MIDI device or listen your MIDI device as an input? This package contains Go bindings for PortMidi. libportmidi (v. 217) is required as a dependency, it's available via apt-get and brew.

apt-get install libportmidi-dev
# or
brew install portmidi

Or, alternatively you can download the source and build it by yourself. See the instructions on PortMidi homepage.

In order to start, go get this repository:

go get github.com/rakyll/portmidi

Usage

Initialize

portmidi.Initialize()

About MIDI Devices

portmidi.CountDevices() // returns the number of MIDI devices
portmidi.Info(deviceID) // returns info about a MIDI device
portmidi.DefaultInputDeviceID() // returns the ID of the system default input
portmidi.DefaultOutputDeviceID() // returns the ID of the system default output

Write to a MIDI Device

out, err := portmidi.NewOutputStream(deviceID, 1024, 0)
if err != nil {
    log.Fatal(err)
}

// note on events to play C major chord
out.WriteShort(0x90, 60, 100)
out.WriteShort(0x90, 64, 100)
out.WriteShort(0x90, 67, 100)

// notes will be sustained for 2 seconds
time.Sleep(2 * time.Second)

// note off events
out.WriteShort(0x80, 60, 100)
out.WriteShort(0x80, 64, 100)
out.WriteShort(0x80, 67, 100)

out.Close()

Read from a MIDI Device

in, err := portmidi.NewInputStream(deviceID, 1024)
if err != nil {
    log.Fatal(err)
}
defer in.Close()

events, err := in.Read(1024)
if err != nil {
    log.Fatal(err)
}

// alternatively you can filter the input to listen
// only a particular set of channels
in.SetChannelMask(portmidi.Channel(1) | portmidi.Channel.(2))
in.Read(1024) // will retrieve events from channel 1 and 2

// or alternatively listen events
ch := in.Listen()
event := <-ch

Cleanup

Cleanup your input and output streams once you're done. Likely to be called on graceful termination.

portmidi.Terminate()

License

Copyright 2013 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

dtl/portmidi