rttyjs/rtty.js

var RTTY = RTTY || {};

var RTTY = function(props) {
    
    this.mark = props.mark;
	this.space = props.space;
	this.baudrate = props.baudrate;
	
	this.bufferEmptyCallback = null;
	this.characterDoneCallback = null;
	
	this.fadeDoneCallback = null;
	
    this.audioCtx = new (window.AudioContext || window.webkitAudioContext)();
	
	this.osc = 0;
	this.freq = this.mark;

	this.buffer = [];
	this.bufferOffset = 0;
	
	this.idleBits = 0;
	
	this.bit = 8;
	this.ct = {};
	this.figsmask = 1<<5;
	this.currentchar = 0x00;
	this.pause = false;
	this.suspend = false;
	this.source = null;
	this.figures = true;
	this.unshift = false;
	this.idle = true;
	this.bufferEmptyCalled = false;
	this.flush = null;
	this.amplitude = 1;
	this.fade = 0;
	
	this.initTables();
	
	this.scriptNode = this.audioCtx.createScriptProcessor(4096, 1, 1);

	this.scriptNode.onaudioprocess = (function(audioProcessingEvent) {
		var inputBuffer = audioProcessingEvent.inputBuffer;
		var outputBuffer = audioProcessingEvent.outputBuffer;
		var inputData = inputBuffer.getChannelData(0);
		var outputData = outputBuffer.getChannelData(0);
		for (var sample = 0; sample < inputBuffer.length; sample++) {
			if (!this.suspend && inputData[sample]==1) { // bit marker
				if (this.idleBits > 0) {
					this.idleBits--;
					if (this.idleBits==0) {
						if (this.characterDoneCallback != null && typeof this.characterDoneCallback == "function") {
							this.characterDoneCallback(bufferLen);
						}
						this.idle = true;
					}
				} else if (this.pause && this.idle) {
					this.suspend = true;
					this.pause = false;
				} else if (this.idle) {
					if (this.flush != null) {
						this.buffer = [];
						this.bufferOffset = 0;
						if (typeof this.flush == "function") {
							this.flush();
						}
						this.flush = null;
					}
					var bufferLen = this.buffer.length - this.bufferOffset;
					if (bufferLen > 0)  {
						this.idle = false;
						if (this.bufferEmptyCalled) {
							this.bufferEmptyCalled = false;
						}
						var next = this.buffer[this.bufferOffset];
						if (++this.bufferOffset * 2 >= this.buffer.length){
							this.buffer  = this.buffer.slice(this.bufferOffset);
							this.bufferOffset = 0;
						}
						switch (next.type) {
						case "char":
							this.currentchar = next.val;
							break;
						case "pause":
							this.idleBits = next.val;
							break;	
						case "callback":
							next.val();
							this.idle = true;
							break;	
						}
					} else if (!this.bufferEmptyCalled) {
						if (this.bufferEmptyCallback != null && typeof this.bufferEmptyCallback == "function") {
							this.bufferEmptyCallback();
							this.bufferEmptyCalled = true;
						} 
					}
				} else {
					if (this.bit==0) { // start
						this.freq = this.space;
					}
					if (this.bit >= 1 && this.bit <= 5) { // data bits
						this.freq = (this.currentchar&1)?this.mark:this.space;
						this.currentchar=this.currentchar>>1;
					}
					if (this.bit==6||this.bit==7) { // stop bits
						this.freq = this.mark;
					}
					if (this.bit==8) {
						this.bit=0;
						this.idle=true;
						if (this.characterDoneCallback != null && typeof this.characterDoneCallback == "function") {
							this.characterDoneCallback(bufferLen);
						}
					} else {
						this.bit++;
					}
				}
			}
			
			outputData[sample] =  this.waveTable[this.osc]*this.amplitude;
			this.osc = (this.osc+this.freq)%this.audioCtx.sampleRate;
			
			if (this.fade > 0 && (this.amplitude + this.fade) > 1) {
				this.fade = 0;
				this.amplitude = 1;
				if (this.fadeDoneCallback != null && typeof this.fadeDoneCallback == "function") {
					this.fadeDoneCallback();
					this.fadeDoneCallback = null;
				}
			} else if (this.fade < 0 && (this.amplitude + this.fade) < 0) {
				this.fade = 0;
				this.amplitude = 0;
				if (this.fadeDoneCallback != null && typeof this.fadeDoneCallback == "function") {
					this.fadeDoneCallback();
					this.fadeDoneCallback = null;
				}
			}
			this.amplitude += this.fade;
		}
	}).bind(this); 
	
}

RTTY.prototype.initTables = function() {
	this.waveTable = new Float32Array(this.audioCtx.sampleRate);
	for (var i=0;i<this.audioCtx.sampleRate;i++) {
		this.waveTable[i] = Math.sin((i/this.audioCtx.sampleRate)*2*Math.PI);
	}
	this.ct = {
		"0": 0x36, "1": 0x37, "2": 0x33, "3": 0x21, "4": 0x2a, "5": 0x30, "6": 0x35, 
		"7": 0x25, "8": 0x26, "9": 0x38, "A": 0x03, "B": 0x19, "C": 0x0e, "D": 0x09, 
		"E": 0x01, "F": 0x0d, "G": 0x1a, "H": 0x14, "I": 0x06, "J": 0x0b, "K": 0x0f, 
		"L": 0x12, "M": 0x1c, "N": 0x0c, "O": 0x18, "P": 0x16, "Q": 0x17, "R": 0x0a, 
		"S": 0x05, "T": 0x10, "U": 0x07, "V": 0x1e, "W": 0x13, "X": 0x1d, "Y": 0x15, 
		"Z": 0x11, "\r": 0x02, "\n": 0x08, "'": 0x2b, "-": 0x23, "_": 0x23, ",": 0x2c, 
		"!": 0x2d, ":": 0x2e, "(": 0x2f, "+": 0x31, ")": 0x32, "#": 0x34, "?": 0x39, 
		"&": 0x3a, ".": 0x3c, "/": 0x3d, ";": 0x3e, "$": 0x29
	}
};


RTTY.prototype.setFade = function(fade, callback) {
	this.fade = fade;
	this.fadeDoneCallback = callback;
}

RTTY.prototype.pauseModulation = function() {
	this.pause = true;
}

RTTY.prototype.resumeModulation = function() {
	this.suspend = false;
}



RTTY.prototype.startSound = function() {
	if (this.source == null) {
		this.idle = true;
		this.amplitude = 0;
		var samplesPerSymbol = Math.floor(this.audioCtx.sampleRate/this.baudrate);
		var myArrayBuffer = this.audioCtx.createBuffer(1, samplesPerSymbol, this.audioCtx.sampleRate);
		this.source = this.audioCtx.createBufferSource();
		this.source.buffer = myArrayBuffer;
		this.source.loop = true;
		
		var tickTrack = myArrayBuffer.getChannelData(0);
		tickTrack[0] = 1;
		
		this.freq = this.mark;
		
		this.source.connect(this.scriptNode);
		this.scriptNode.connect(this.audioCtx.destination);
		this.source.start();	
		
		this.setFade(.01, null);	
	} 
}

RTTY.prototype.stopSound = function() {
	if (this.source != null) {
		var me = this
		this.flushBuffer(function(){
			me.setFade(-.01, function(){
				setTimeout(function(){
					me.source.stop();
	 				me.scriptNode.disconnect();
	 				me.source = null;
				}, 500);
			});
		});
	}
}

RTTY.prototype.flushBuffer = function(callback) {
	if (callback == null) {
		callback=function(){};
	}
	this.flush = callback;
}

RTTY.prototype.invert = function() {
	var x = this.mark;
	if (this.freq==this.mark) {
		this.freq=this.space;
	} else {
		this.freq=this.mark;
	}
	this.mark = this.space;
	this.space = x;
}


RTTY.prototype.modulate = function(str) {
	for (var i = 0, len = str.length; i < len; i++) {
		this.modulateChar(str[i]);
	}
}

RTTY.prototype.modulateChar = function(c) {
	var baudot
	
	var c = c.toUpperCase();
	
	switch (c) {
		case 0x00: // null
			this.pushChar(0x00); // null
			break;
		case 0x0a: // lf
			this.pushChar(0x02); // cr
			this.pushChar(0x08); // lf
			break;
		case ' ': // space
			// if we print a space in figures mode, terminals set to
			// unshift on space will unshift. Remember that, so that if a
			// figures character needs to be printed, we can turn figures
			// mode back on before printing it.
			if (this.figures) {
				this.unshift = true;
			}
			this.pushChar(0x04);
			break;
		case '@': // Change @ to (at)
			this.figs();
			this.pushChar(this.ct['(']);
			this.ltrs();
			this.pushChar(this.ct['A']);
			this.pushChar(this.ct['T']);
			this.figs();
			this.pushChar(this.ct[')']);
			break;
		case '"': // use two single quotes as a double quote
			this.figs();
			this.pushChar(this.ct["'"]);
			this.pushChar(this.ct["'"]);
			break;
		default:
			baudot=this.ct[c];
			if (baudot!=undefined) {
				// correction for unshift on space
				if ((baudot&this.figsmask)&&this.figures&&this.unshift) {
					this.figs();
				}
				if ((baudot&this.figsmask)&&!this.figures) {
					this.figs();
				}
				if (!(baudot&this.figsmask)&&this.figures) {
					this.ltrs();
				}
				this.pushChar(baudot);
			}
			break;
	}

}

RTTY.prototype.pushChar = function(c) {
	this.buffer.push({
		type: "char",
		val: c
	});

}

RTTY.prototype.pushPause = function(p) {
	this.buffer.push({
		type: "pause",
		val: p
	});
}

RTTY.prototype.pushCallback = function(callback) {
	this.buffer.push({
		type: "callback",
		val: callback
	});
}


RTTY.prototype.figs = function() {
	this.pushChar(0x1b); // figs
	this.figures=true;
	this.unshift=false;
}

RTTY.prototype.ltrs = function() {
	this.pushChar(0x1f); // ltrs
	this.figures=false;
	this.unshift=false;
}