kc85tape.html

<html>
<head>
	<title></title>
	<script type="text/javascript" src="jquery-2.1.3.min.js"></script>
</head>
<body>

</body>
<script type="text/javascript">
	
	SAMPLE_RATE = 44100;
	
	// Nullbit:       f = 2400 Hz
	ZERO_BIT = 1950;	
	
	// Einsbit:       f = 1200 Hz
	ONE_BIT = 1050;
	
	//Trennzeichen:  f =  600 Hz
	SEPARATOR = 557;

	function add_wave(buffer, frequency) {

		for (var i=0; i<Math.floor(SAMPLE_RATE/frequency); i++) {
			buffer.push(Math.sin(2*Math.PI*i*frequency/SAMPLE_RATE));
		}

	}

	function add_waves(buffer, frequency, max) {

		for (var i=0; i<max; i++) {
			add_wave(buffer, frequency);
		}

	}

	// Byteaufbau:   8 Datenbits (Je 0- oder 1-Bit)
	//	             1 Trennzeichen
	//               mit Bit 0 beginnend
	function convert_byte_to_audio(buffer, byte_to_send) {

		for (var i=0; i<8; i++) {
			add_wave(buffer, (((byte_to_send >> i) & 0x01) == 1) ? ONE_BIT : ZERO_BIT);
		}
		add_wave(buffer, SEPARATOR);

	};

	// Blockaufbau:  - Vorton: aus Schwingungen mit 1200 Hz (Einsbit)
	//                 bestehend
	//                 * erster Block: langer Vorton, etwa 8000 Schwingungen
	//                 * folgende Blöcke: je nach Verarbeitungszeit
	//                   (für MC-Programm 160 Schwingungen)
	//               - 1 Trennzeichen
	//               - 1 Byte Block-Nr. (siehe nächster Abschnitt)
	//               - 128 Datenbytes (siehe nächster Abschnitt)
	//               - 1 Byte Datensumme (siehe nächster Abschnitt)	
	function create_block(buffer, block_number, blocks_total, data) {

		var checksum = 0;
		add_waves(buffer, ONE_BIT, block_number == 1 ? 8000 : 160);
		add_wave(buffer, SEPARATOR);

		convert_byte_to_audio(buffer, block_number == blocks_total ? 0xFF : block_number);

		for (var i=(block_number-1) * 128; i<(block_number == blocks_total ? data.length : block_number * 128); i++) {
			checksum += data.charCodeAt(i)
			convert_byte_to_audio(buffer, data.charCodeAt(i));
		}
		convert_byte_to_audio(buffer, checksum & 0xFF);
	}

	function convert_file_to_audio(buffer, data) {

		var data_length = data.length;
		var blocks_total = Math.ceil(data_length/128);

		for (var block_number=1; block_number<=blocks_total; block_number++) {
			create_block(buffer, block_number, blocks_total, data);
		}

	};


	$(document).ready(function() {

		$.get('DIGGER-3.KCC', {}, function(response) {
			var data = [];
			convert_file_to_audio(data, response);

			buffer = audio_context.createBuffer(1, data.length, SAMPLE_RATE);

			bufferSource = audio_context.createBufferSource();
			bufferSource.buffer = buffer;
			
			soundData = buffer.getChannelData(0);
			for (var i = 0; i < soundData.length; i++) {
			  soundData[i] = data[i];
			}
			bufferSource.connect(audio_context.destination);
			bufferSource.start(0);

		});

	});

  var audio_context, oscillator;
 
  (function init(where){
	try {
	  audio_context = new (where.AudioContext || where.webkitAudioContext);
	} catch (e) {
	  alert('No web audio oscillator support in this browser');
	}
  }(window));

</script>
</html>