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standard_midi_file.ksy
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standard_midi_file.ksy
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meta:
id: standard_midi_file
title: Standard MIDI file
file-extension:
- mid
- midi
- smf
xref:
justsolve: MIDI
loc:
- fdd000102 # MIDI Sequence Data
- fdd000119 # Standard MIDI File
mime: audio/midi
pronom: x-fmt/230
wikidata: Q10610388
license: CC0-1.0
imports:
- /common/vlq_base128_be
endian: be
doc: |
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.
seq:
- id: hdr
type: header
- id: tracks
type: track
repeat: expr
repeat-expr: hdr.num_tracks
types:
header:
seq:
- id: magic
contents: "MThd"
- id: len_header
type: u4
- id: format
type: u2
- id: num_tracks
type: u2
- id: division
type: s2
track:
seq:
- id: magic
contents: "MTrk"
- id: len_events
type: u4
- id: events
type: track_events
size: len_events
track_events:
seq:
- id: event
type: track_event
repeat: eos
track_event:
seq:
- id: v_time
type: vlq_base128_be
- id: event_header
type: u1
- id: meta_event_body
type: meta_event_body
if: event_header == 0xff
- id: sysex_body
type: sysex_event_body
if: event_header == 0xf0
- id: event_body
type:
switch-on: event_type
cases:
0x80: note_off_event
0x90: note_on_event
0xa0: polyphonic_pressure_event
0xb0: controller_event
0xc0: program_change_event
0xd0: channel_pressure_event
0xe0: pitch_bend_event
instances:
event_type:
value: event_header & 0xf0
channel:
value: event_header & 0xf
if: event_type != 0xf0
meta_event_body:
seq:
- id: meta_type
type: u1
enum: meta_type_enum
- id: len
type: vlq_base128_be
- id: body
size: len.value
enums:
meta_type_enum:
0x00: sequence_number
0x01: text_event
0x02: copyright
0x03: sequence_track_name
0x04: instrument_name
0x05: lyric_text
0x06: marker_text
0x07: cue_point
0x20: midi_channel_prefix_assignment
0x2f: end_of_track
0x51: tempo
0x54: smpte_offset
0x58: time_signature
0x59: key_signature
0x7f: sequencer_specific_event
note_off_event:
seq:
- id: note
type: u1
- id: velocity
type: u1
note_on_event:
seq:
- id: note
type: u1
- id: velocity
type: u1
polyphonic_pressure_event:
seq:
- id: note
type: u1
- id: pressure
type: u1
controller_event:
seq:
- id: controller
type: u1
- id: value
type: u1
program_change_event:
seq:
- id: program
type: u1
channel_pressure_event:
seq:
- id: pressure
type: u1
pitch_bend_event:
seq:
- id: b1
type: u1
- id: b2
type: u1
instances:
bend_value:
value: (b2 << 7) + b1 - 0x4000
adj_bend_value:
value: bend_value - 0x4000
sysex_event_body:
seq:
- id: len
type: vlq_base128_be
- id: data
size: len.value