Standard MIDI file: Go parsing library

Standard MIDI file, typically known just as "MID", is a standard way to serialize series of MIDI events, which is a protocol used in many music synthesizers to transfer music data: notes being played, effects being applied, etc.

Internally, file consists of a header and series of tracks, every track listing MIDI events with certain header designating time these events are happening.

NOTE: Rarely, MIDI files employ certain stateful compression scheme to avoid storing certain elements of further elements, instead reusing them from events which happened earlier in the stream. Kaitai Struct (as of v0.9) is currently unable to parse these, but files employing this mechanism are relatively rare.

File extension

["mid", "midi", "smf"]

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of Standard MIDI file using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Go source code to parse Standard MIDI file

standard_midi_file.go

Download 

// Code generated by kaitai-struct-compiler from a .ksy source file. DO NOT EDIT.

import (
	"github.com/kaitai-io/kaitai_struct_go_runtime/kaitai"
	"bytes"
)


/**
 * Standard MIDI file, typically known just as "MID", is a standard way
 * to serialize series of MIDI events, which is a protocol used in many
 * music synthesizers to transfer music data: notes being played,
 * effects being applied, etc.
 * 
 * Internally, file consists of a header and series of tracks, every
 * track listing MIDI events with certain header designating time these
 * events are happening.
 * 
 * NOTE: Rarely, MIDI files employ certain stateful compression scheme
 * to avoid storing certain elements of further elements, instead
 * reusing them from events which happened earlier in the
 * stream. Kaitai Struct (as of v0.9) is currently unable to parse
 * these, but files employing this mechanism are relatively rare.
 */
type StandardMidiFile struct {
	Hdr *StandardMidiFile_Header
	Tracks []*StandardMidiFile_Track
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent interface{}
}
func NewStandardMidiFile() *StandardMidiFile {
	return &StandardMidiFile{
	}
}

func (this *StandardMidiFile) Read(io *kaitai.Stream, parent interface{}, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp1 := NewStandardMidiFile_Header()
	err = tmp1.Read(this._io, this, this._root)
	if err != nil {
		return err
	}
	this.Hdr = tmp1
	for i := 0; i < int(this.Hdr.NumTracks); i++ {
		_ = i
		tmp2 := NewStandardMidiFile_Track()
		err = tmp2.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.Tracks = append(this.Tracks, tmp2)
	}
	return err
}
type StandardMidiFile_TrackEvents struct {
	Event []*StandardMidiFile_TrackEvent
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_Track
}
func NewStandardMidiFile_TrackEvents() *StandardMidiFile_TrackEvents {
	return &StandardMidiFile_TrackEvents{
	}
}

func (this *StandardMidiFile_TrackEvents) Read(io *kaitai.Stream, parent *StandardMidiFile_Track, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	for i := 1;; i++ {
		tmp3, err := this._io.EOF()
		if err != nil {
			return err
		}
		if tmp3 {
			break
		}
		tmp4 := NewStandardMidiFile_TrackEvent()
		err = tmp4.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.Event = append(this.Event, tmp4)
	}
	return err
}
type StandardMidiFile_TrackEvent struct {
	VTime *VlqBase128Be
	EventHeader uint8
	MetaEventBody *StandardMidiFile_MetaEventBody
	SysexBody *StandardMidiFile_SysexEventBody
	EventBody interface{}
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvents
	_f_eventType bool
	eventType int
	_f_channel bool
	channel int
}
func NewStandardMidiFile_TrackEvent() *StandardMidiFile_TrackEvent {
	return &StandardMidiFile_TrackEvent{
	}
}

func (this *StandardMidiFile_TrackEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvents, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp5 := NewVlqBase128Be()
	err = tmp5.Read(this._io, this, nil)
	if err != nil {
		return err
	}
	this.VTime = tmp5
	tmp6, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.EventHeader = tmp6
	if (this.EventHeader == 255) {
		tmp7 := NewStandardMidiFile_MetaEventBody()
		err = tmp7.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.MetaEventBody = tmp7
	}
	if (this.EventHeader == 240) {
		tmp8 := NewStandardMidiFile_SysexEventBody()
		err = tmp8.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.SysexBody = tmp8
	}
	tmp9, err := this.EventType()
	if err != nil {
		return err
	}
	switch (tmp9) {
	case 224:
		tmp10 := NewStandardMidiFile_PitchBendEvent()
		err = tmp10.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp10
	case 144:
		tmp11 := NewStandardMidiFile_NoteOnEvent()
		err = tmp11.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp11
	case 208:
		tmp12 := NewStandardMidiFile_ChannelPressureEvent()
		err = tmp12.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp12
	case 192:
		tmp13 := NewStandardMidiFile_ProgramChangeEvent()
		err = tmp13.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp13
	case 160:
		tmp14 := NewStandardMidiFile_PolyphonicPressureEvent()
		err = tmp14.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp14
	case 176:
		tmp15 := NewStandardMidiFile_ControllerEvent()
		err = tmp15.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp15
	case 128:
		tmp16 := NewStandardMidiFile_NoteOffEvent()
		err = tmp16.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.EventBody = tmp16
	}
	return err
}
func (this *StandardMidiFile_TrackEvent) EventType() (v int, err error) {
	if (this._f_eventType) {
		return this.eventType, nil
	}
	this.eventType = int((this.EventHeader & 240))
	this._f_eventType = true
	return this.eventType, nil
}
func (this *StandardMidiFile_TrackEvent) Channel() (v int, err error) {
	if (this._f_channel) {
		return this.channel, nil
	}
	tmp17, err := this.EventType()
	if err != nil {
		return 0, err
	}
	if (tmp17 != 240) {
		this.channel = int((this.EventHeader & 15))
	}
	this._f_channel = true
	return this.channel, nil
}
type StandardMidiFile_PitchBendEvent struct {
	B1 uint8
	B2 uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
	_f_bendValue bool
	bendValue int
	_f_adjBendValue bool
	adjBendValue int
}
func NewStandardMidiFile_PitchBendEvent() *StandardMidiFile_PitchBendEvent {
	return &StandardMidiFile_PitchBendEvent{
	}
}

func (this *StandardMidiFile_PitchBendEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp18, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.B1 = tmp18
	tmp19, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.B2 = tmp19
	return err
}
func (this *StandardMidiFile_PitchBendEvent) BendValue() (v int, err error) {
	if (this._f_bendValue) {
		return this.bendValue, nil
	}
	this.bendValue = int((((this.B2 << 7) + this.B1) - 16384))
	this._f_bendValue = true
	return this.bendValue, nil
}
func (this *StandardMidiFile_PitchBendEvent) AdjBendValue() (v int, err error) {
	if (this._f_adjBendValue) {
		return this.adjBendValue, nil
	}
	tmp20, err := this.BendValue()
	if err != nil {
		return 0, err
	}
	this.adjBendValue = int((tmp20 - 16384))
	this._f_adjBendValue = true
	return this.adjBendValue, nil
}
type StandardMidiFile_ProgramChangeEvent struct {
	Program uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_ProgramChangeEvent() *StandardMidiFile_ProgramChangeEvent {
	return &StandardMidiFile_ProgramChangeEvent{
	}
}

func (this *StandardMidiFile_ProgramChangeEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp21, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Program = tmp21
	return err
}
type StandardMidiFile_NoteOnEvent struct {
	Note uint8
	Velocity uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_NoteOnEvent() *StandardMidiFile_NoteOnEvent {
	return &StandardMidiFile_NoteOnEvent{
	}
}

func (this *StandardMidiFile_NoteOnEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp22, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Note = tmp22
	tmp23, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Velocity = tmp23
	return err
}
type StandardMidiFile_PolyphonicPressureEvent struct {
	Note uint8
	Pressure uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_PolyphonicPressureEvent() *StandardMidiFile_PolyphonicPressureEvent {
	return &StandardMidiFile_PolyphonicPressureEvent{
	}
}

func (this *StandardMidiFile_PolyphonicPressureEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp24, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Note = tmp24
	tmp25, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Pressure = tmp25
	return err
}
type StandardMidiFile_Track struct {
	Magic []byte
	LenEvents uint32
	Events *StandardMidiFile_TrackEvents
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile
	_raw_Events []byte
}
func NewStandardMidiFile_Track() *StandardMidiFile_Track {
	return &StandardMidiFile_Track{
	}
}

func (this *StandardMidiFile_Track) Read(io *kaitai.Stream, parent *StandardMidiFile, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp26, err := this._io.ReadBytes(int(4))
	if err != nil {
		return err
	}
	tmp26 = tmp26
	this.Magic = tmp26
	if !(bytes.Equal(this.Magic, []uint8{77, 84, 114, 107})) {
		return kaitai.NewValidationNotEqualError([]uint8{77, 84, 114, 107}, this.Magic, this._io, "/types/track/seq/0")
	}
	tmp27, err := this._io.ReadU4be()
	if err != nil {
		return err
	}
	this.LenEvents = uint32(tmp27)
	tmp28, err := this._io.ReadBytes(int(this.LenEvents))
	if err != nil {
		return err
	}
	tmp28 = tmp28
	this._raw_Events = tmp28
	_io__raw_Events := kaitai.NewStream(bytes.NewReader(this._raw_Events))
	tmp29 := NewStandardMidiFile_TrackEvents()
	err = tmp29.Read(_io__raw_Events, this, this._root)
	if err != nil {
		return err
	}
	this.Events = tmp29
	return err
}

type StandardMidiFile_MetaEventBody_MetaTypeEnum int
const (
	StandardMidiFile_MetaEventBody_MetaTypeEnum__SequenceNumber StandardMidiFile_MetaEventBody_MetaTypeEnum = 0
	StandardMidiFile_MetaEventBody_MetaTypeEnum__TextEvent StandardMidiFile_MetaEventBody_MetaTypeEnum = 1
	StandardMidiFile_MetaEventBody_MetaTypeEnum__Copyright StandardMidiFile_MetaEventBody_MetaTypeEnum = 2
	StandardMidiFile_MetaEventBody_MetaTypeEnum__SequenceTrackName StandardMidiFile_MetaEventBody_MetaTypeEnum = 3
	StandardMidiFile_MetaEventBody_MetaTypeEnum__InstrumentName StandardMidiFile_MetaEventBody_MetaTypeEnum = 4
	StandardMidiFile_MetaEventBody_MetaTypeEnum__LyricText StandardMidiFile_MetaEventBody_MetaTypeEnum = 5
	StandardMidiFile_MetaEventBody_MetaTypeEnum__MarkerText StandardMidiFile_MetaEventBody_MetaTypeEnum = 6
	StandardMidiFile_MetaEventBody_MetaTypeEnum__CuePoint StandardMidiFile_MetaEventBody_MetaTypeEnum = 7
	StandardMidiFile_MetaEventBody_MetaTypeEnum__MidiChannelPrefixAssignment StandardMidiFile_MetaEventBody_MetaTypeEnum = 32
	StandardMidiFile_MetaEventBody_MetaTypeEnum__EndOfTrack StandardMidiFile_MetaEventBody_MetaTypeEnum = 47
	StandardMidiFile_MetaEventBody_MetaTypeEnum__Tempo StandardMidiFile_MetaEventBody_MetaTypeEnum = 81
	StandardMidiFile_MetaEventBody_MetaTypeEnum__SmpteOffset StandardMidiFile_MetaEventBody_MetaTypeEnum = 84
	StandardMidiFile_MetaEventBody_MetaTypeEnum__TimeSignature StandardMidiFile_MetaEventBody_MetaTypeEnum = 88
	StandardMidiFile_MetaEventBody_MetaTypeEnum__KeySignature StandardMidiFile_MetaEventBody_MetaTypeEnum = 89
	StandardMidiFile_MetaEventBody_MetaTypeEnum__SequencerSpecificEvent StandardMidiFile_MetaEventBody_MetaTypeEnum = 127
)
type StandardMidiFile_MetaEventBody struct {
	MetaType StandardMidiFile_MetaEventBody_MetaTypeEnum
	Len *VlqBase128Be
	Body []byte
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_MetaEventBody() *StandardMidiFile_MetaEventBody {
	return &StandardMidiFile_MetaEventBody{
	}
}

func (this *StandardMidiFile_MetaEventBody) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp30, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.MetaType = StandardMidiFile_MetaEventBody_MetaTypeEnum(tmp30)
	tmp31 := NewVlqBase128Be()
	err = tmp31.Read(this._io, this, nil)
	if err != nil {
		return err
	}
	this.Len = tmp31
	tmp32, err := this.Len.Value()
	if err != nil {
		return err
	}
	tmp33, err := this._io.ReadBytes(int(tmp32))
	if err != nil {
		return err
	}
	tmp33 = tmp33
	this.Body = tmp33
	return err
}
type StandardMidiFile_ControllerEvent struct {
	Controller uint8
	Value uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_ControllerEvent() *StandardMidiFile_ControllerEvent {
	return &StandardMidiFile_ControllerEvent{
	}
}

func (this *StandardMidiFile_ControllerEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp34, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Controller = tmp34
	tmp35, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Value = tmp35
	return err
}
type StandardMidiFile_Header struct {
	Magic []byte
	LenHeader uint32
	Format uint16
	NumTracks uint16
	Division int16
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile
}
func NewStandardMidiFile_Header() *StandardMidiFile_Header {
	return &StandardMidiFile_Header{
	}
}

func (this *StandardMidiFile_Header) Read(io *kaitai.Stream, parent *StandardMidiFile, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp36, err := this._io.ReadBytes(int(4))
	if err != nil {
		return err
	}
	tmp36 = tmp36
	this.Magic = tmp36
	if !(bytes.Equal(this.Magic, []uint8{77, 84, 104, 100})) {
		return kaitai.NewValidationNotEqualError([]uint8{77, 84, 104, 100}, this.Magic, this._io, "/types/header/seq/0")
	}
	tmp37, err := this._io.ReadU4be()
	if err != nil {
		return err
	}
	this.LenHeader = uint32(tmp37)
	tmp38, err := this._io.ReadU2be()
	if err != nil {
		return err
	}
	this.Format = uint16(tmp38)
	tmp39, err := this._io.ReadU2be()
	if err != nil {
		return err
	}
	this.NumTracks = uint16(tmp39)
	tmp40, err := this._io.ReadS2be()
	if err != nil {
		return err
	}
	this.Division = int16(tmp40)
	return err
}
type StandardMidiFile_SysexEventBody struct {
	Len *VlqBase128Be
	Data []byte
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_SysexEventBody() *StandardMidiFile_SysexEventBody {
	return &StandardMidiFile_SysexEventBody{
	}
}

func (this *StandardMidiFile_SysexEventBody) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp41 := NewVlqBase128Be()
	err = tmp41.Read(this._io, this, nil)
	if err != nil {
		return err
	}
	this.Len = tmp41
	tmp42, err := this.Len.Value()
	if err != nil {
		return err
	}
	tmp43, err := this._io.ReadBytes(int(tmp42))
	if err != nil {
		return err
	}
	tmp43 = tmp43
	this.Data = tmp43
	return err
}
type StandardMidiFile_NoteOffEvent struct {
	Note uint8
	Velocity uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_NoteOffEvent() *StandardMidiFile_NoteOffEvent {
	return &StandardMidiFile_NoteOffEvent{
	}
}

func (this *StandardMidiFile_NoteOffEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp44, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Note = tmp44
	tmp45, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Velocity = tmp45
	return err
}
type StandardMidiFile_ChannelPressureEvent struct {
	Pressure uint8
	_io *kaitai.Stream
	_root *StandardMidiFile
	_parent *StandardMidiFile_TrackEvent
}
func NewStandardMidiFile_ChannelPressureEvent() *StandardMidiFile_ChannelPressureEvent {
	return &StandardMidiFile_ChannelPressureEvent{
	}
}

func (this *StandardMidiFile_ChannelPressureEvent) Read(io *kaitai.Stream, parent *StandardMidiFile_TrackEvent, root *StandardMidiFile) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp46, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Pressure = tmp46
	return err
}