Standard MIDI file: GraphViz block diagram (.dot) source

Standard MIDI file, typically knows 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.

GraphViz block diagram source

standard_midi_file.dot

digraph {
	rankdir=LR;
	node [shape=plaintext];
	subgraph cluster__standard_midi_file {
		label="StandardMidiFile";
		graph[style=dotted];

		standard_midi_file__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
			<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
			<TR><TD PORT="hdr_pos">0</TD><TD PORT="hdr_size">14</TD><TD>Header</TD><TD PORT="hdr_type">hdr</TD></TR>
			<TR><TD PORT="tracks_pos">14</TD><TD PORT="tracks_size">...</TD><TD>Track</TD><TD PORT="tracks_type">tracks</TD></TR>
			<TR><TD COLSPAN="4" PORT="tracks__repeat">repeat hdr.num_tracks times</TD></TR>
		</TABLE>>];
		subgraph cluster__track_events {
			label="StandardMidiFile::TrackEvents";
			graph[style=dotted];

			track_events__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="event_pos">0</TD><TD PORT="event_size">...</TD><TD>TrackEvent</TD><TD PORT="event_type">event</TD></TR>
				<TR><TD COLSPAN="4" PORT="event__repeat">repeat to end of stream</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__track_event {
			label="StandardMidiFile::TrackEvent";
			graph[style=dotted];

			track_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="v_time_pos">0</TD><TD PORT="v_time_size">...</TD><TD>VlqBase128Be</TD><TD PORT="v_time_type">v_time</TD></TR>
				<TR><TD PORT="event_header_pos">...</TD><TD PORT="event_header_size">1</TD><TD>u1</TD><TD PORT="event_header_type">event_header</TD></TR>
				<TR><TD PORT="meta_event_body_pos">...</TD><TD PORT="meta_event_body_size">...</TD><TD>MetaEventBody</TD><TD PORT="meta_event_body_type">meta_event_body</TD></TR>
				<TR><TD PORT="sysex_body_pos">...</TD><TD PORT="sysex_body_size">...</TD><TD>SysexEventBody</TD><TD PORT="sysex_body_type">sysex_body</TD></TR>
				<TR><TD PORT="event_body_pos">...</TD><TD PORT="event_body_size">...</TD><TD>switch (event_type)</TD><TD PORT="event_body_type">event_body</TD></TR>
			</TABLE>>];
			track_event__inst__event_type [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">id</TD><TD BGCOLOR="#E0FFE0">value</TD></TR>
				<TR><TD>event_type</TD><TD>(event_header &amp; 240)</TD></TR>
			</TABLE>>];
			track_event__inst__channel [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">id</TD><TD BGCOLOR="#E0FFE0">value</TD></TR>
				<TR><TD>channel</TD><TD>(event_header &amp; 15)</TD></TR>
			</TABLE>>];
track_event__seq_event_body_switch [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
	<TR><TD BGCOLOR="#F0F2E4">case</TD><TD BGCOLOR="#F0F2E4">type</TD></TR>
	<TR><TD>224</TD><TD PORT="case0">PitchBendEvent</TD></TR>
	<TR><TD>144</TD><TD PORT="case1">NoteOnEvent</TD></TR>
	<TR><TD>208</TD><TD PORT="case2">ChannelPressureEvent</TD></TR>
	<TR><TD>192</TD><TD PORT="case3">ProgramChangeEvent</TD></TR>
	<TR><TD>160</TD><TD PORT="case4">PolyphonicPressureEvent</TD></TR>
	<TR><TD>176</TD><TD PORT="case5">ControllerEvent</TD></TR>
	<TR><TD>128</TD><TD PORT="case6">NoteOffEvent</TD></TR>
</TABLE>>];
		}
		subgraph cluster__pitch_bend_event {
			label="StandardMidiFile::PitchBendEvent";
			graph[style=dotted];

			pitch_bend_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="b1_pos">0</TD><TD PORT="b1_size">1</TD><TD>u1</TD><TD PORT="b1_type">b1</TD></TR>
				<TR><TD PORT="b2_pos">1</TD><TD PORT="b2_size">1</TD><TD>u1</TD><TD PORT="b2_type">b2</TD></TR>
			</TABLE>>];
			pitch_bend_event__inst__bend_value [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">id</TD><TD BGCOLOR="#E0FFE0">value</TD></TR>
				<TR><TD>bend_value</TD><TD>(((b2 &lt;&lt; 7) + b1) - 16384)</TD></TR>
			</TABLE>>];
			pitch_bend_event__inst__adj_bend_value [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">id</TD><TD BGCOLOR="#E0FFE0">value</TD></TR>
				<TR><TD>adj_bend_value</TD><TD>(bend_value - 16384)</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__program_change_event {
			label="StandardMidiFile::ProgramChangeEvent";
			graph[style=dotted];

			program_change_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="program_pos">0</TD><TD PORT="program_size">1</TD><TD>u1</TD><TD PORT="program_type">program</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__note_on_event {
			label="StandardMidiFile::NoteOnEvent";
			graph[style=dotted];

			note_on_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="note_pos">0</TD><TD PORT="note_size">1</TD><TD>u1</TD><TD PORT="note_type">note</TD></TR>
				<TR><TD PORT="velocity_pos">1</TD><TD PORT="velocity_size">1</TD><TD>u1</TD><TD PORT="velocity_type">velocity</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__polyphonic_pressure_event {
			label="StandardMidiFile::PolyphonicPressureEvent";
			graph[style=dotted];

			polyphonic_pressure_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="note_pos">0</TD><TD PORT="note_size">1</TD><TD>u1</TD><TD PORT="note_type">note</TD></TR>
				<TR><TD PORT="pressure_pos">1</TD><TD PORT="pressure_size">1</TD><TD>u1</TD><TD PORT="pressure_type">pressure</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__track {
			label="StandardMidiFile::Track";
			graph[style=dotted];

			track__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="magic_pos">0</TD><TD PORT="magic_size">4</TD><TD>4D 54 72 6B</TD><TD PORT="magic_type">magic</TD></TR>
				<TR><TD PORT="len_events_pos">4</TD><TD PORT="len_events_size">4</TD><TD>u4be</TD><TD PORT="len_events_type">len_events</TD></TR>
				<TR><TD PORT="events_pos">8</TD><TD PORT="events_size">len_events</TD><TD>TrackEvents</TD><TD PORT="events_type">events</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__meta_event_body {
			label="StandardMidiFile::MetaEventBody";
			graph[style=dotted];

			meta_event_body__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="meta_type_pos">0</TD><TD PORT="meta_type_size">1</TD><TD>u1→MetaTypeEnum</TD><TD PORT="meta_type_type">meta_type</TD></TR>
				<TR><TD PORT="len_pos">1</TD><TD PORT="len_size">...</TD><TD>VlqBase128Be</TD><TD PORT="len_type">len</TD></TR>
				<TR><TD PORT="body_pos">...</TD><TD PORT="body_size">len.value</TD><TD></TD><TD PORT="body_type">body</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__controller_event {
			label="StandardMidiFile::ControllerEvent";
			graph[style=dotted];

			controller_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="controller_pos">0</TD><TD PORT="controller_size">1</TD><TD>u1</TD><TD PORT="controller_type">controller</TD></TR>
				<TR><TD PORT="value_pos">1</TD><TD PORT="value_size">1</TD><TD>u1</TD><TD PORT="value_type">value</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__header {
			label="StandardMidiFile::Header";
			graph[style=dotted];

			header__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="magic_pos">0</TD><TD PORT="magic_size">4</TD><TD>4D 54 68 64</TD><TD PORT="magic_type">magic</TD></TR>
				<TR><TD PORT="len_header_pos">4</TD><TD PORT="len_header_size">4</TD><TD>u4be</TD><TD PORT="len_header_type">len_header</TD></TR>
				<TR><TD PORT="format_pos">8</TD><TD PORT="format_size">2</TD><TD>u2be</TD><TD PORT="format_type">format</TD></TR>
				<TR><TD PORT="num_tracks_pos">10</TD><TD PORT="num_tracks_size">2</TD><TD>u2be</TD><TD PORT="num_tracks_type">num_tracks</TD></TR>
				<TR><TD PORT="division_pos">12</TD><TD PORT="division_size">2</TD><TD>s2be</TD><TD PORT="division_type">division</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__sysex_event_body {
			label="StandardMidiFile::SysexEventBody";
			graph[style=dotted];

			sysex_event_body__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="len_pos">0</TD><TD PORT="len_size">...</TD><TD>VlqBase128Be</TD><TD PORT="len_type">len</TD></TR>
				<TR><TD PORT="data_pos">...</TD><TD PORT="data_size">len.value</TD><TD></TD><TD PORT="data_type">data</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__note_off_event {
			label="StandardMidiFile::NoteOffEvent";
			graph[style=dotted];

			note_off_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="note_pos">0</TD><TD PORT="note_size">1</TD><TD>u1</TD><TD PORT="note_type">note</TD></TR>
				<TR><TD PORT="velocity_pos">1</TD><TD PORT="velocity_size">1</TD><TD>u1</TD><TD PORT="velocity_type">velocity</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__channel_pressure_event {
			label="StandardMidiFile::ChannelPressureEvent";
			graph[style=dotted];

			channel_pressure_event__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="pressure_pos">0</TD><TD PORT="pressure_size">1</TD><TD>u1</TD><TD PORT="pressure_type">pressure</TD></TR>
			</TABLE>>];
		}
	}
	standard_midi_file__seq:hdr_type -> header__seq [style=bold];
	standard_midi_file__seq:tracks_type -> track__seq [style=bold];
	header__seq:num_tracks_type -> standard_midi_file__seq:tracks__repeat [color="#404040"];
	track_events__seq:event_type -> track_event__seq [style=bold];
	track_event__seq:v_time_type -> vlq_base128_be__seq [style=bold];
	track_event__seq:meta_event_body_type -> meta_event_body__seq [style=bold];
	track_event__seq:sysex_body_type -> sysex_event_body__seq [style=bold];
	track_event__seq:event_body_type -> track_event__seq_event_body_switch [style=bold];
	track_event__seq_event_body_switch:case0 -> pitch_bend_event__seq [style=bold];
	track_event__seq_event_body_switch:case1 -> note_on_event__seq [style=bold];
	track_event__seq_event_body_switch:case2 -> channel_pressure_event__seq [style=bold];
	track_event__seq_event_body_switch:case3 -> program_change_event__seq [style=bold];
	track_event__seq_event_body_switch:case4 -> polyphonic_pressure_event__seq [style=bold];
	track_event__seq_event_body_switch:case5 -> controller_event__seq [style=bold];
	track_event__seq_event_body_switch:case6 -> note_off_event__seq [style=bold];
	track_event__inst__event_type:event_type_type -> track_event__seq:event_body_type [color="#404040"];
	track_event__seq:event_header_type -> track_event__inst__event_type [color="#404040"];
	track_event__seq:event_header_type -> track_event__inst__channel [color="#404040"];
	pitch_bend_event__seq:b2_type -> pitch_bend_event__inst__bend_value [color="#404040"];
	pitch_bend_event__seq:b1_type -> pitch_bend_event__inst__bend_value [color="#404040"];
	pitch_bend_event__inst__bend_value:bend_value_type -> pitch_bend_event__inst__adj_bend_value [color="#404040"];
	track__seq:len_events_type -> track__seq:events_size [color="#404040"];
	track__seq:events_type -> track_events__seq [style=bold];
	meta_event_body__seq:len_type -> vlq_base128_be__seq [style=bold];
	vlq_base128_be__inst__value:value_type -> meta_event_body__seq:body_size [color="#404040"];
	sysex_event_body__seq:len_type -> vlq_base128_be__seq [style=bold];
	vlq_base128_be__inst__value:value_type -> sysex_event_body__seq:data_size [color="#404040"];
}