Tone.js/test/deps/audiobuffer-to-wav.js

/**
 * The MIT License (MIT) Copyright (c) 2015 Jam3
 */
define(function(){
	function audioBufferToWav(buffer, opt) {
		opt = opt || {};

		var numChannels = buffer.numberOfChannels;
		var sampleRate = buffer.sampleRate;
		var format = opt.float32 ? 3 : 1;
		var bitDepth = format === 3 ? 32 : 16;

		var result;
		if (numChannels === 2) {
			result = interleave(buffer.getChannelData(0), buffer.getChannelData(1));
		} else {
			result = buffer.getChannelData(0);
		}

		return encodeWAV(result, format, sampleRate, numChannels, bitDepth);
	}

	function encodeWAV(samples, format, sampleRate, numChannels, bitDepth) {
		var bytesPerSample = bitDepth / 8;
		var blockAlign = numChannels * bytesPerSample;

		var buffer = new ArrayBuffer(44 + samples.length * bytesPerSample);
		var view = new DataView(buffer);

		/* RIFF identifier */
		writeString(view, 0, "RIFF");
		/* RIFF chunk length */
		view.setUint32(4, 36 + samples.length * bytesPerSample, true);
		/* RIFF type */
		writeString(view, 8, "WAVE");
		/* format chunk identifier */
		writeString(view, 12, "fmt ");
		/* format chunk length */
		view.setUint32(16, 16, true);
		/* sample format (raw) */
		view.setUint16(20, format, true);
		/* channel count */
		view.setUint16(22, numChannels, true);
		/* sample rate */
		view.setUint32(24, sampleRate, true);
		/* byte rate (sample rate * block align) */
		view.setUint32(28, sampleRate * blockAlign, true);
		/* block align (channel count * bytes per sample) */
		view.setUint16(32, blockAlign, true);
		/* bits per sample */
		view.setUint16(34, bitDepth, true);
		/* data chunk identifier */
		writeString(view, 36, "data");
		/* data chunk length */
		view.setUint32(40, samples.length * bytesPerSample, true);
		if (format === 1) { // Raw PCM
			floatTo16BitPCM(view, 44, samples);
		} else {
			writeFloat32(view, 44, samples);
		}

		return buffer;
	}

	function interleave(inputL, inputR) {
		var length = inputL.length + inputR.length;
		var result = new Float32Array(length);

		var index = 0;
		var inputIndex = 0;

		while (index < length) {
			result[index++] = inputL[inputIndex];
			result[index++] = inputR[inputIndex];
			inputIndex++;
		}
		return result;
	}

	function writeFloat32(output, offset, input) {
		for (var i = 0; i < input.length; i++, offset += 4) {
			output.setFloat32(offset, input[i], true);
		}
	}

	function floatTo16BitPCM(output, offset, input) {
		for (var i = 0; i < input.length; i++, offset += 2) {
			var s = Math.max(-1, Math.min(1, input[i]));
			output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
		}
	}

	function writeString(view, offset, string) {
		for (var i = 0; i < string.length; i++) {
			view.setUint8(offset + i, string.charCodeAt(i));
		}
	}
	return audioBufferToWav;
});