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@@ -0,0 +1,238 @@
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+/*
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+class to parse the .mid file format
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+(depends on stream.js)
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+*/
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+function MidiFile(data) {
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+ function readChunk(stream) {
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+ var id = stream.read(4);
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+ var length = stream.readInt32();
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+ return {
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+ 'id': id,
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+ 'length': length,
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+ 'data': stream.read(length)
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+ };
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+ }
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+
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+ var lastEventTypeByte;
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+
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+ function readEvent(stream) {
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+ var event = {};
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+ event.deltaTime = stream.readVarInt();
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+ var eventTypeByte = stream.readInt8();
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+ if ((eventTypeByte & 0xf0) == 0xf0) {
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+ /* system / meta event */
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+ if (eventTypeByte == 0xff) {
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+ /* meta event */
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+ event.type = 'meta';
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+ var subtypeByte = stream.readInt8();
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+ var length = stream.readVarInt();
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+ switch(subtypeByte) {
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+ case 0x00:
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+ event.subtype = 'sequenceNumber';
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+ if (length != 2) throw "Expected length for sequenceNumber event is 2, got " + length;
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+ event.number = stream.readInt16();
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+ return event;
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+ case 0x01:
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+ event.subtype = 'text';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x02:
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+ event.subtype = 'copyrightNotice';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x03:
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+ event.subtype = 'trackName';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x04:
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+ event.subtype = 'instrumentName';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x05:
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+ event.subtype = 'lyrics';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x06:
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+ event.subtype = 'marker';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x07:
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+ event.subtype = 'cuePoint';
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+ event.text = stream.read(length);
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+ return event;
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+ case 0x20:
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+ event.subtype = 'midiChannelPrefix';
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+ if (length != 1) throw "Expected length for midiChannelPrefix event is 1, got " + length;
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+ event.channel = stream.readInt8();
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+ return event;
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+ case 0x2f:
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+ event.subtype = 'endOfTrack';
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+ if (length != 0) throw "Expected length for endOfTrack event is 0, got " + length;
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+ return event;
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+ case 0x51:
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+ event.subtype = 'setTempo';
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+ if (length != 3) throw "Expected length for setTempo event is 3, got " + length;
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+ event.microsecondsPerBeat = (
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+ (stream.readInt8() << 16)
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+ + (stream.readInt8() << 8)
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+ + stream.readInt8()
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+ )
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+ return event;
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+ case 0x54:
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+ event.subtype = 'smpteOffset';
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+ if (length != 5) throw "Expected length for smpteOffset event is 5, got " + length;
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+ var hourByte = stream.readInt8();
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+ event.frameRate = {
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+ 0x00: 24, 0x20: 25, 0x40: 29, 0x60: 30
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+ }[hourByte & 0x60];
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+ event.hour = hourByte & 0x1f;
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+ event.min = stream.readInt8();
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+ event.sec = stream.readInt8();
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+ event.frame = stream.readInt8();
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+ event.subframe = stream.readInt8();
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+ return event;
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+ case 0x58:
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+ event.subtype = 'timeSignature';
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+ if (length != 4) throw "Expected length for timeSignature event is 4, got " + length;
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+ event.numerator = stream.readInt8();
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+ event.denominator = Math.pow(2, stream.readInt8());
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+ event.metronome = stream.readInt8();
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+ event.thirtyseconds = stream.readInt8();
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+ return event;
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+ case 0x59:
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+ event.subtype = 'keySignature';
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+ if (length != 2) throw "Expected length for keySignature event is 2, got " + length;
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+ event.key = stream.readInt8(true);
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+ event.scale = stream.readInt8();
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+ return event;
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+ case 0x7f:
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+ event.subtype = 'sequencerSpecific';
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+ event.data = stream.read(length);
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+ return event;
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+ default:
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+ // console.log("Unrecognised meta event subtype: " + subtypeByte);
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+ event.subtype = 'unknown'
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+ event.data = stream.read(length);
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+ return event;
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+ }
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+ event.data = stream.read(length);
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+ return event;
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+ } else if (eventTypeByte == 0xf0) {
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+ event.type = 'sysEx';
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+ var length = stream.readVarInt();
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+ event.data = stream.read(length);
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+ return event;
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+ } else if (eventTypeByte == 0xf7) {
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+ event.type = 'dividedSysEx';
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+ var length = stream.readVarInt();
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+ event.data = stream.read(length);
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+ return event;
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+ } else {
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+ throw "Unrecognised MIDI event type byte: " + eventTypeByte;
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+ }
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+ } else {
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+ /* channel event */
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+ var param1;
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+ if ((eventTypeByte & 0x80) == 0) {
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+ /* running status - reuse lastEventTypeByte as the event type.
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+ eventTypeByte is actually the first parameter
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+ */
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+ param1 = eventTypeByte;
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+ eventTypeByte = lastEventTypeByte;
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+ } else {
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+ param1 = stream.readInt8();
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+ lastEventTypeByte = eventTypeByte;
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+ }
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+ var eventType = eventTypeByte >> 4;
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+ event.channel = eventTypeByte & 0x0f;
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+ event.type = 'channel';
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+ switch (eventType) {
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+ case 0x08:
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+ event.subtype = 'noteOff';
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+ event.noteNumber = param1;
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+ event.velocity = stream.readInt8();
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+ return event;
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+ case 0x09:
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+ event.noteNumber = param1;
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+ event.velocity = stream.readInt8();
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+ if (event.velocity == 0) {
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+ event.subtype = 'noteOff';
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+ } else {
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+ event.subtype = 'noteOn';
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+ }
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+ return event;
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+ case 0x0a:
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+ event.subtype = 'noteAftertouch';
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+ event.noteNumber = param1;
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+ event.amount = stream.readInt8();
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+ return event;
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+ case 0x0b:
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+ event.subtype = 'controller';
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+ event.controllerType = param1;
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+ event.value = stream.readInt8();
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+ return event;
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+ case 0x0c:
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+ event.subtype = 'programChange';
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+ event.programNumber = param1;
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+ return event;
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+ case 0x0d:
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+ event.subtype = 'channelAftertouch';
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+ event.amount = param1;
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+ return event;
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+ case 0x0e:
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+ event.subtype = 'pitchBend';
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+ event.value = param1 + (stream.readInt8() << 7);
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+ return event;
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+ default:
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+ throw "Unrecognised MIDI event type: " + eventType
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+ /*
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+ console.log("Unrecognised MIDI event type: " + eventType);
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+ stream.readInt8();
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+ event.subtype = 'unknown';
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+ return event;
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+ */
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+ }
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+ }
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+ }
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+
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+ stream = Stream(data);
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+ var headerChunk = readChunk(stream);
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+ if (headerChunk.id != 'MThd' || headerChunk.length != 6) {
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+ throw "Bad .mid file - header not found";
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+ }
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+ var headerStream = Stream(headerChunk.data);
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+ var formatType = headerStream.readInt16();
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+ var trackCount = headerStream.readInt16();
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+ var timeDivision = headerStream.readInt16();
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+
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+ if (timeDivision & 0x8000) {
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+ throw "Expressing time division in SMTPE frames is not supported yet"
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+ } else {
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+ ticksPerBeat = timeDivision;
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+ }
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+
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+ var header = {
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+ 'formatType': formatType,
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+ 'trackCount': trackCount,
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+ 'ticksPerBeat': ticksPerBeat
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+ }
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+ var tracks = [];
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+ for (var i = 0; i < header.trackCount; i++) {
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+ tracks[i] = [];
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+ var trackChunk = readChunk(stream);
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+ if (trackChunk.id != 'MTrk') {
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+ throw "Unexpected chunk - expected MTrk, got "+ trackChunk.id;
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+ }
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+ var trackStream = Stream(trackChunk.data);
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+ while (!trackStream.eof()) {
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+ var event = readEvent(trackStream);
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+ tracks[i].push(event);
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+ //console.log(event);
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+ }
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+ }
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+
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+ return {
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+ 'header': header,
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+ 'tracks': tracks
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+ }
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+}
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