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MidiMusic.md

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SMF structure

MidiMusic class is to represent a Standard MIDI File format compliant song.

An SMF consists of (1) a header chunk and (2) track chunks. A track is represented as MidiTrack class, and it just contains a set of MidiMessage structures. A MidiMessage is a timed MidiEvent structure, where "time" is represented (in Int32) as a "delta time".

  • MidiMusic
    • deltaTimeSpec part of header chunk (negative SMTPe or positive clock count for quarter notes)
    • format part of header chunk (0 or 1)
    • MidiTrack list
      • MidiMessage list
        • DeltaTime
        • MidiEvent
          • byte array data for F0 (sysex) and FF (meta) messages. null for non-Fx event.
          • int32 value, which bundles status byte, MSB, and LSB.

There is MIDI 2.0 feature parity, named Midi2Music, Midi2Track, and Ump.

  • Midi2Music
    • deltaTimeSpec same as above
    • Midi2Track list
      • Ump list

For the details of the format, see MIDI2_FORMATS.md.

Design notes

simple raw bytes oriented API

Regarding how to represent MIDI messages, there are two kinds of MIDI libraries:

  • has strongly-typed MIDI messages for each message type e.g. NoteOnMessage, NoteOffMessage, PitchBendMessage etc.
  • represents MIDI messages only in byte arrays.

managed-midi is basically latter, passing raw bytes around. It is for better performance - MIDI access APIs shouldn't have to spend computing resources on converting bytes and strongly-typed arrays around.

But for MidiPlayer, it does convert those raw bytes to those MidiMessage arrays. SmfReader parses SMFs to MidiMusic, and SmfWriter writes to MutableList<Byte>. For most of MIDI programmers would just need these classes to deal with SMFs.

There are also for MIDI 2.0 support: Midi2MusicReader and Midi2MusicWriter.