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audioBuffer.js
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audioBuffer.js
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export default audioBufferToWav;
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));
}
}