midi

README

midi

Modular library for reading and writing of MIDI messages with Go.

This package is meant for users that have some knowledge of the MIDI standards. Beginners, and people on the run might want to look at the porcelain package https://gitlab.com/gomidi/mid.

Status

stable

• Go version: >= 1.10
• OS/architectures: everywhere Go runs (tested on Linux and Windows).

Installation

go get gitlab.com/gomidi/midi/...

Documentation

see http://godoc.org/gitlab.com/gomidi/midi

Features

• implementation of complete MIDI standard (live and SMF data)
• reading and optional writing with "running status"
• seemless integration with io.Reader and io.Writer
• allows the reuse of same libraries for live writing and writing to SMF files
• provide building blocks for other MIDI libraries and applications
• stable API
• no dependencies outside the standard library
• small modular core packages
• typed Messages
• pure Go library (no C, no assembler)

Non-Goals

• constructing of MIDI time code messages
• Multidimensional Polyphonic Expression (MPE)
• dealing with the inner structure of sysex messages
• connection to MIDI devices (for this combine it with https://gitlab.com/gomidi/connect)
• CLI tools

Usage / Example

package main

import (
    "bytes"
    "fmt"
    . "gitlab.com/gomidi/midi/midimessage/channel"
    "gitlab.com/gomidi/midi/midimessage/realtime"
    "gitlab.com/gomidi/midi/midireader"
    "gitlab.com/gomidi/midi/midiwriter"
    "io"
    "gitlab.com/gomidi/midi"
)

func main() {
    var bf bytes.Buffer

    wr := midiwriter.New(&bf)
    wr.Write(Channel2.Pitchbend(5000))
    wr.Write(Channel2.NoteOn(65, 90))
    wr.Write(realtime.Reset)
    wr.Write(Channel2.NoteOff(65))

    rthandler := func(m realtime.Message) {
        fmt.Printf("Realtime: %s\n", m)
    }

    rd := midireader.New(bytes.NewReader(bf.Bytes()), rthandler)

    var m midi.Message
    var err error

    for {
        m, err = rd.Read()

        // breaking at least with io.EOF
        if err != nil {
            break
        }

        // inspect
        fmt.Println(m)

        switch v := m.(type) {
        case NoteOn:
            fmt.Printf("NoteOn at channel %v: key: %v velocity: %v\n", v.Channel(), v.Key(), v.Velocity())
        case NoteOff:
            fmt.Printf("NoteOff at channel %v: key: %v\n", v.Channel(), v.Key())
        }

    }

    if err != io.EOF {
        panic("error: " + err.Error())
    }

    // Output:
    // channel.Pitchbend channel 2 value 5000 absValue 13192
    // channel.NoteOn channel 2 key 65 velocity 90
    // NoteOn at channel 2: key: 65 velocity: 90
    // Realtime: Reset
    // channel.NoteOff channel 2 key 65
    // NoteOff at channel 2: key: 65
}

Modularity

This package is divided into small subpackages, so that you only need to import what you really need. This keeps packages and dependencies small, better testable and should result in a smaller memory footprint which should help smaller devices.

For reading and writing of live and SMF MIDI data io.Readers are accepted as input and io.Writers as output. Furthermore there are common interfaces for live and SMF MIDI data handling: midi.Reader and midi.Writer. The typed MIDI messages used in each case are the same.

To connect with MIDI libraries expecting and returning plain bytes (e.g. over the wire), use midiio subpackage.

Perfomance

On my laptop, writing noteon and noteoff ("live")

BenchmarkSameChannel            123 ns/op  12 B/op  3 allocs/op
BenchmarkAlternatingChannel     123 ns/op  12 B/op  3 allocs/op
BenchmarkRunningStatusDisabled  110 ns/op  12 B/op  3 allocs/op

On my laptop, reading noteon and noteoff ("live") ("Samechannel" makes use of running status byte).

BenchmarkSameChannel            351 ns/op  12 B/op  7 allocs/op
BenchmarkAlternatingChannel     425 ns/op  14 B/op  9 allocs/op

License

MIT (see LICENSE file)

Credits

Inspiration and low level code for MIDI reading (see internal midilib package) came from the http://github.com/afandian/go-midi package of Joe Wass which also helped as a starting point for the reading of SMF files.

Alternatives

Matt Aimonetti is also working on MIDI inside https://github.com/mattetti/audio but I didn't try it.

Documentation

Overview

Package midi provides interfaces for reading and writing of MIDI messages.

Since they are handled slightly different, this packages introduces the terminology of "live" MIDI reading/writing for dealing with MIDI messages as "over the wire" (in realtime) as opposed to smf MIDI reading/writing to Standard MIDI Files (SMF).

However both variants can be used with io.Writer and io.Reader and can thus be "streamed".

This package provides a Reader and Writer interface that is common to live and SMF MIDI handling. This should allow to easily develop transformations (e.g. quantization, filtering) that may be used in both cases.

If you want a comfortable common package providing everything at a high level, use the porcelain package

gitlab.com/gomidi/mid

The underlying core implementations can be found here:

gitlab.com/gomidi/midi/midireader (live reading)
gitlab.com/gomidi/midi/midiwriter (live writing)
gitlab.com/gomidi/midi/smf/smfreader   (SMF reading)
gitlab.com/gomidi/midi/smf/smfwriter   (SMF writing)
gitlab.com/gomidi/midi/smf/smftrack    (SMF modification)

The core of the MIDI messages that can be written or analyzed can be found here:

gitlab.com/gomidi/midi/midimessage/channel    (Channel Messages)
gitlab.com/gomidi/midi/midimessage/meta       (Meta Messages)
gitlab.com/gomidi/midi/midimessage/realtime   (System Realtime Messages)
gitlab.com/gomidi/midi/midimessage/syscommon  (System Common messages)
gitlab.com/gomidi/midi/midimessage/sysex      (System Exclusive messages)

Please keep in mind that that not all kinds of MIDI messages can be used in both scenarios.

System Realtime and System Common Messages are restricted to "over the wire", while Meta Messages are restricted to SMF files. However System Realtime and System Common Messages can be saved inside a SMF file which the help of SysEx escaping (F7).

Index

• Variables
• type Message
• type ReadCloser
• type Reader
• type WriteCloser
• type Writer

Variables

var ErrUnexpectedEOF = fmt.Errorf("Unexpected End of File found.")

ErrUnexpectedEOF is returned, when an unexspected end of file is reached.

Types

type Message

type Message interface {
	// String inspects the MIDI message in an informative way
	String() string

	// Raw returns the raw bytes of the MIDI message
	Raw() []byte
}

Message is a MIDI message

type ReadCloser

type ReadCloser interface {
	Reader
	Close() error
}

ReadCloser is a Reader that must be closed at the end of reading.

type Reader

type Reader interface {
	// Read reads a MIDI message
	Read() (Message, error)
}

Reader reads MIDI messages

type WriteCloser

type WriteCloser interface {
	Writer
	Close() error
}

WriteCloser is a Writer that must be closed at the end of writing.

type Writer

type Writer interface {
	// Write writes the given MIDI message and returns any error
	Write(Message) error
}

Writer writes MIDI messages