132 lines
3.1 KiB
JavaScript
132 lines
3.1 KiB
JavaScript
var recLength = 0,
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recBuffersL = [],
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recBuffersR = [],
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sampleRate;
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this.onmessage = function(e){
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switch(e.data.command){
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case 'init':
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init(e.data.config);
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break;
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case 'record':
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record(e.data.buffer);
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break;
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case 'exportWAV':
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exportWAV(e.data.type);
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break;
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case 'getBuffer':
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getBuffer();
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break;
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case 'clear':
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clear();
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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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}
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function record(inputBuffer){
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recBuffersL.push(inputBuffer[0]);
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recBuffersR.push(inputBuffer[1]);
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recLength += inputBuffer[0].length;
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}
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function exportWAV(type){
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var bufferL = mergeBuffers(recBuffersL, recLength);
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var bufferR = mergeBuffers(recBuffersR, recLength);
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var interleaved = interleave(bufferL, bufferR);
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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(audioBlob);
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}
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function getBuffer() {
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var buffers = [];
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buffers.push( mergeBuffers(recBuffersL, recLength) );
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buffers.push( mergeBuffers(recBuffersR, recLength) );
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this.postMessage(buffers);
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}
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function clear(){
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recLength = 0;
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recBuffersL = [];
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recBuffersR = [];
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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,
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inputIndex = 0;
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while (index < 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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/* RIFF identifier */
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writeString(view, 0, 'RIFF');
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/* RIFF chunk length */
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view.setUint32(4, 36 + samples.length * 2, true);
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/* RIFF type */
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writeString(view, 8, 'WAVE');
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/* format chunk identifier */
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writeString(view, 12, 'fmt ');
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/* format chunk length */
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view.setUint32(16, 16, true);
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/* sample format (raw) */
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view.setUint16(20, 1, true);
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/* channel count */
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view.setUint16(22, 2, true);
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/* sample rate */
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view.setUint32(24, sampleRate, true);
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/* byte rate (sample rate * block align) */
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view.setUint32(28, sampleRate * 4, true);
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/* block align (channel count * bytes per sample) */
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view.setUint16(32, 4, true);
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/* bits per sample */
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view.setUint16(34, 16, true);
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/* data chunk identifier */
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writeString(view, 36, 'data');
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/* data chunk length */
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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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