nicholas@1: /**
nicholas@1:  * core.js
nicholas@1:  * 
nicholas@1:  * Main script to run, calls all other core functions and manages loading/store to backend.
nicholas@1:  * Also contains all global variables.
nicholas@1:  */
nicholas@1: 
nicholas@1: /* create the web audio API context and store in audioContext*/
nicholas@1: var audioContext;
nicholas@2: var projectXML;
nicholas@1: var audioEngineContext;
nicholas@1: 
nicholas@1: window.onload = function() {
nicholas@1: 	// Function called once the browser has loaded all files.
nicholas@1: 	// This should perform any initial commands such as structure / loading documents
nicholas@1: 	
nicholas@1: 	// Create a web audio API context
nicholas@1: 	// NORE: Currently this will only work with webkit browsers (Chrome/Safari)!
nicholas@1: 	audioContext = new webkitAudioContext;
nicholas@1: 	
nicholas@1: 	// Create the audio engine object
nicholas@1: 	audioEngineContext = new AudioEngine();
nicholas@1: }
nicholas@1: 
nicholas@1: function loadProjectSpec(url) {
nicholas@1: 	// Load the project document from the given URL, decode the XML and instruct audioEngine to get audio data
nicholas@1: 	// If url is null, request client to upload project XML document
nicholas@2: 	var r = new XMLHttpRequest();
nicholas@2: 	r.open('GET',url,true);
nicholas@2: 	r.onload = function() {
nicholas@2: 		loadProjectSpecCallback(r.response);
nicholas@2: 	}
nicholas@2: 	r.send();
nicholas@2: }
nicholas@2: 
nicholas@2: function loadProjectSpecCallback(response) {
nicholas@2: 	// Function called after asynchronous download of XML project specification
nicholas@2: 	var decode = $.parseXML(response);
nicholas@2: 	projectXML = $(decode);
nicholas@2: 	
nicholas@2: 	// Now extract the setup tag
nicholas@2: 	var xmlSetup = projectXML.find('setup');
nicholas@2: 	var interfaceType = xmlSetup[0].attributes['interface'];
nicholas@2: 	var interfaceJS = document.createElement('script');
nicholas@2: 	interfaceJS.setAttribute("type","text/javascript");
nicholas@2: 	if (interfaceType.value == 'APE') {
nicholas@2: 		interfaceJS.setAttribute("src","ape.js");
nicholas@2: 	}
nicholas@2: 	document.getElementsByTagName("head")[0].appendChild(interfaceJS);
nicholas@1: }
nicholas@1: 
nicholas@1: function createProjectSave(destURL) {
nicholas@1: 	// Save the data from interface into XML and send to destURL
nicholas@1: 	// If destURL is null then download XML in client
nicholas@1: }
nicholas@1: 
nicholas@1: function AudioEngine() {
nicholas@1: 	
nicholas@1: 	// Create two output paths, the main outputGain and fooGain.
nicholas@1: 	// Output gain is default to 1 and any items for playback route here
nicholas@1: 	// Foo gain is used for analysis to ensure paths get processed, but are not heard
nicholas@1: 	// because web audio will optimise and any route which does not go to the destination gets ignored.
nicholas@1: 	this.outputGain = audioContext.createGain();
nicholas@1: 	this.fooGain = audioContext.createGain();
nicholas@1: 	this.fooGain.gain = 0;
nicholas@1: 	
nicholas@1: 	// Connect both gains to output
nicholas@1: 	this.outputGain.connect(audioContext.destination);
nicholas@1: 	this.fooGain.connect(audioContext.destination);
nicholas@1: 	
nicholas@1: 	// Create store for new audioObjects
nicholas@1: 	this.audioObjects = [];
nicholas@1: 	
nicholas@1: 	this.play = function() {
nicholas@1: 		// Send play command to all playback buffers for synchronised start
nicholas@1: 		// Also start timer callbacks to detect if playback has finished
nicholas@1: 	}
nicholas@1: 	
nicholas@1: 	this.stop = function() {
nicholas@1: 		// Send stop and reset command to all playback buffers
nicholas@1: 	}
nicholas@1: 	
nicholas@1: 	this.newTrack = function(url) {
nicholas@1: 		// Pull data from given URL into new audio buffer
nicholas@1: 		// URLs must either be from the same source OR be setup to 'Access-Control-Allow-Origin'
nicholas@1: 		var request = new XMLHttpRequest();
nicholas@1: 		request.open('GET',url,true);
nicholas@1: 		request.responseType = 'arraybuffer';
nicholas@1: 		// Create the audioObject with ID of the new track length;
nicholas@1: 		audioObjectId = this.audioObjects.length
nicholas@1: 		this.audioObjects[audioObjectId] = new audioObject(audioObjectId);
nicholas@1: 		
nicholas@1: 		// Create callback to decode the data asynchronously
nicholas@1: 		request.onload = function() {
nicholas@1: 			audioContext.decodeAudioData(request.response, function(decodedData) {
nicholas@1: 				audioObj = audioEngineContext.audioObjects[audioObjectId];
nicholas@1: 				audioObj.buffer = decodedData;
nicholas@1: 				audioObj.bufferNode.buffer = audioObj.buffer;
nicholas@1: 				audioObj.state = 1;
nicholas@1: 			}, console.log("Err - Buffer not added to " + audioObjectId));
nicholas@1: 		}
nicholas@1: 		request.send();
nicholas@1: 	}
nicholas@1: 	
nicholas@1: }
nicholas@1: 
nicholas@1: function audioObject(id) {
nicholas@1: 	// The main buffer object with common control nodes to the AudioEngine
nicholas@1: 	
nicholas@1: 	this.id = id;
nicholas@1: 	this.state = 0; // 0 - no data, 1 - ready
nicholas@1: 	
nicholas@1: 	// Create a buffer and external gain control to allow internal patching of effects and volume leveling.
nicholas@1: 	this.bufferNode = audioContext.createBufferSource();
nicholas@1: 	this.outputGain = audioContext.createGain();
nicholas@1: 	
nicholas@1: 	// Connect buffer to the audio graph
nicholas@1: 	this.bufferNode.connect(this.outputGain);
nicholas@1: 	this.outputGain.connect(audioEngineContext.outputGain);
nicholas@1: 	
nicholas@1: 	// the audiobuffer is not designed for multi-start playback
nicholas@1: 	// When stopeed, the buffer node is deleted and recreated with the stored buffer.
nicholas@1: 	this.buffer;
nicholas@1: 	
nicholas@1: 	this.play = function(startTime) {
nicholas@1: 		this.bufferNode.start(startTime);
nicholas@1: 	}
nicholas@1: 	
nicholas@1: 	this.stop = function() {
nicholas@1: 		this.bufferNode.stop(0);
nicholas@1: 		this.bufferNode = audioContext.createBufferSource();
nicholas@1: 		this.bufferNode.connect(this.outputGain);
nicholas@1: 		this.bufferNode.buffer = this.buffer;
nicholas@1: 	}
nicholas@1: 	
nicholas@1: }