1 files changed, 171 insertions, 0 deletions
diff --git a/replayer.js b/replayer.js
new file mode 100644
index 0000000..d1c8b4b
--- /dev/null
+++ b/replayer.js
@@ -0,0 +1,171 @@
+function Replayer(midiFile, synth) {
+	var trackStates = [];
+	var beatsPerMinute = 120;
+	var ticksPerBeat = midiFile.header.ticksPerBeat;
+	var channelCount = 16;
+	
+	for (var i = 0; i < midiFile.tracks.length; i++) {
+		trackStates[i] = {
+			'nextEventIndex': 0,
+			'ticksToNextEvent': (
+				midiFile.tracks[i].length ?
+					midiFile.tracks[i][0].deltaTime :
+					null
+			)
+		};
+	}
+	
+	function Channel() {
+		
+		var generatorsByNote = {};
+		var currentProgram = PianoProgram;
+		
+		function noteOn(note, velocity) {
+			if (generatorsByNote[note] && !generatorsByNote[note].released) {
+				/* playing same note before releasing the last one. BOO */
+				generatorsByNote[note].noteOff(); /* TODO: check whether we ought to be passing a velocity in */
+			}
+			generator = currentProgram.createNote(note, velocity);
+			synth.addGenerator(generator);
+			generatorsByNote[note] = generator;
+		}
+		function noteOff(note, velocity) {
+			if (generatorsByNote[note] && !generatorsByNote[note].released) {
+				generatorsByNote[note].noteOff(velocity);
+			}
+		}
+		function setProgram(programNumber) {
+			currentProgram = PROGRAMS[programNumber] || PianoProgram;
+		}
+		
+		return {
+			'noteOn': noteOn,
+			'noteOff': noteOff,
+			'setProgram': setProgram
+		}
+	}
+	
+	var channels = [];
+	for (var i = 0; i < channelCount; i++) {
+		channels[i] = Channel();
+	}
+	
+	var nextEventInfo;
+	var samplesToNextEvent = 0;
+	
+	function getNextEvent() {
+		var ticksToNextEvent = null;
+		var nextEventTrack = null;
+		var nextEventIndex = null;
+		
+		for (var i = 0; i < trackStates.length; i++) {
+			if (
+				trackStates[i].ticksToNextEvent != null
+				&& (ticksToNextEvent == null || trackStates[i].ticksToNextEvent < ticksToNextEvent)
+			) {
+				ticksToNextEvent = trackStates[i].ticksToNextEvent;
+				nextEventTrack = i;
+				nextEventIndex = trackStates[i].nextEventIndex;
+			}
+		}
+		if (nextEventTrack != null) {
+			/* consume event from that track */
+			var nextEvent = midiFile.tracks[nextEventTrack][nextEventIndex];
+			if (midiFile.tracks[nextEventTrack][nextEventIndex + 1]) {
+				trackStates[nextEventTrack].ticksToNextEvent += midiFile.tracks[nextEventTrack][nextEventIndex + 1].deltaTime;
+			} else {
+				trackStates[nextEventTrack].ticksToNextEvent = null;
+			}
+			trackStates[nextEventTrack].nextEventIndex += 1;
+			/* advance timings on all tracks by ticksToNextEvent */
+			for (var i = 0; i < trackStates.length; i++) {
+				if (trackStates[i].ticksToNextEvent != null) {
+					trackStates[i].ticksToNextEvent -= ticksToNextEvent
+				}
+			}
+			nextEventInfo = {
+				'ticksToEvent': ticksToNextEvent,
+				'event': nextEvent,
+				'track': nextEventTrack
+			}
+			var beatsToNextEvent = ticksToNextEvent / ticksPerBeat;
+			var secondsToNextEvent = beatsToNextEvent / (beatsPerMinute / 60);
+			samplesToNextEvent += secondsToNextEvent * synth.sampleRate;
+		} else {
+			nextEventInfo = null;
+			samplesToNextEvent = null;
+			self.finished = true;
+		}
+	}
+	
+	getNextEvent();
+	
+	function generate(samples) {
+		var data = new Array(samples*2);
+		var samplesRemaining = samples;
+		var dataOffset = 0;
+		
+		while (true) {
+			if (samplesToNextEvent != null && samplesToNextEvent <= samplesRemaining) {
+				/* generate samplesToNextEvent samples, process event and repeat */
+				var samplesToGenerate = Math.ceil(samplesToNextEvent);
+				if (samplesToGenerate > 0) {
+					synth.generateIntoBuffer(samplesToGenerate, data, dataOffset);
+					dataOffset += samplesToGenerate * 2;
+					samplesRemaining -= samplesToGenerate;
+					samplesToNextEvent -= samplesToGenerate;
+				}
+				
+				handleEvent();
+				getNextEvent();
+			} else {
+				/* generate samples to end of buffer */
+				if (samplesRemaining > 0) {
+					synth.generateIntoBuffer(samplesRemaining, data, dataOffset);
+					samplesToNextEvent -= samplesRemaining;
+				}
+				break;
+			}
+		}
+		return data;
+	}
+	
+	function handleEvent() {
+		var event = nextEventInfo.event;
+		switch (event.type) {
+			case 'meta':
+				switch (event.subtype) {
+					case 'setTempo':
+						beatsPerMinute = 60000000 / event.microsecondsPerBeat
+				}
+				break;
+			case 'channel':
+				switch (event.subtype) {
+					case 'noteOn':
+						channels[event.channel].noteOn(event.noteNumber, event.velocity);
+						break;
+					case 'noteOff':
+						channels[event.channel].noteOff(event.noteNumber, event.velocity);
+						break;
+					case 'programChange':
+						//console.log('program change to ' + event.programNumber);
+						channels[event.channel].setProgram(event.programNumber);
+						break;
+				}
+				break;
+		}
+	}
+	
+	function replay(audio) {
+		console.log('replay');
+		audio.write(generate(44100));
+		setTimeout(function() {replay(audio)}, 10);
+	}
+	
+	var self = {
+		'replay': replay,
+		'generate': generate,
+		'finished': false
+	}
+	return self;
+}