How to convert received MidiPacket into NoteOn, NoteOff, etc messages?

[Gilianp]

Hi, thanks again for the plugin :)

How to convert received MidiPacket into NoteOn, NoteOff, etc messages? When I subscribed in onMidiDataReceived, only MidiPacket are received, but I can't figure out how convert then in "parsed (NoteOn, NoteOff, etc)" midi messages properly for use in my app. Thanks

[mortenboye]

MidiPackets/Messages are usually between 1 and 3 bytes long, with each bytes containing different data depending on the type of midi message.

Full spec. can be found here (requires (free) login).

But for NoteOn and Off, the three bytes in a message will look like this:
TTTTCCCC 0KKKKKKK 0VVVVVVV

where the 4 T-bits define the type of Midi message
the 4 C-bits define the Midi channel
the 7 K-bits define the key of the note
the 7 V-bits define the velocity of the note

and you can handle that using this as a starting point:

var data = packet.data;
if (data.length == 3) {
  var status = data[0];
  var type = status & 0xF0;
  var channel = status & 0x0F;
  var note = data[1];
  var vel = data[2];

  if (type == 0x90) {
    // Note On
  } else if (type == 0x80) {
    // Note Off
  }
}

Remember that a NoteOn message (0x90) with a Velocity of 0, signifies the same as a NoteOff message for the same key.