116 lines
3.2 KiB
JavaScript
116 lines
3.2 KiB
JavaScript
/* Recorder.js worker — https://github.com/mattdiamond/Recorderjs */
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var recLength = 0,
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recBuffers = [],
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sampleRate,
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numChannels;
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this.onmessage = function(e) {
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switch (e.data.command) {
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case 'init': init(e.data.config); break;
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case 'record': record(e.data.buffer); break;
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case 'exportWAV': exportWAV(e.data.type); break;
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case 'getBuffer': getBuffer(); break;
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case 'clear': clear(); break;
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}
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};
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function init(config) {
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sampleRate = config.sampleRate;
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numChannels = config.numChannels;
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initBuffers();
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}
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function record(inputBuffer) {
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for (var channel = 0; channel < numChannels; channel++) {
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recBuffers[channel].push(inputBuffer[channel]);
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}
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recLength += inputBuffer[0].length;
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}
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function exportWAV(type) {
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var buffers = [];
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for (var channel = 0; channel < numChannels; channel++) {
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buffers.push(mergeBuffers(recBuffers[channel], recLength));
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}
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var interleaved = numChannels === 2
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? interleave(buffers[0], buffers[1])
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: buffers[0];
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var dataview = encodeWAV(interleaved);
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var audioBlob = new Blob([dataview], { type: type });
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this.postMessage({ command: 'exportWAV', data: audioBlob });
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}
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function getBuffer() {
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var buffers = [];
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for (var channel = 0; channel < numChannels; channel++) {
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buffers.push(mergeBuffers(recBuffers[channel], recLength));
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}
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this.postMessage({ command: 'getBuffer', data: buffers });
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}
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function clear() {
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recLength = 0;
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recBuffers = [];
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initBuffers();
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}
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function initBuffers() {
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for (var channel = 0; channel < numChannels; channel++) {
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recBuffers[channel] = [];
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}
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}
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function mergeBuffers(recBuffers, recLength) {
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var result = new Float32Array(recLength);
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var offset = 0;
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for (var i = 0; i < recBuffers.length; i++) {
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result.set(recBuffers[i], offset);
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offset += recBuffers[i].length;
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}
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return result;
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}
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function interleave(inputL, inputR) {
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var length = inputL.length + inputR.length;
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var result = new Float32Array(length);
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var index = 0, inputIndex = 0;
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while (inputIndex < inputL.length) {
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result[index++] = inputL[inputIndex];
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result[index++] = inputR[inputIndex];
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inputIndex++;
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}
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return result;
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}
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function floatTo16BitPCM(output, offset, input) {
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for (var i = 0; i < input.length; i++, offset += 2) {
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var s = Math.max(-1, Math.min(1, input[i]));
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output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
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}
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}
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function writeString(view, offset, string) {
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for (var i = 0; i < string.length; i++) {
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view.setUint8(offset + i, string.charCodeAt(i));
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}
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}
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function encodeWAV(samples) {
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var buffer = new ArrayBuffer(44 + samples.length * 2);
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var view = new DataView(buffer);
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writeString(view, 0, 'RIFF');
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view.setUint32(4, 36 + samples.length * 2, true);
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writeString(view, 8, 'WAVE');
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writeString(view, 12, 'fmt ');
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view.setUint32(16, 16, true);
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view.setUint16(20, 1, true);
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view.setUint16(22, numChannels, true);
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view.setUint32(24, sampleRate, true);
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view.setUint32(28, sampleRate * numChannels * 2, true);
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view.setUint16(32, numChannels * 2, true);
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view.setUint16(34, 16, true);
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writeString(view, 36, 'data');
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view.setUint32(40, samples.length * 2, true);
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floatTo16BitPCM(view, 44, samples);
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return view;
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}
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