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130 lines
2.7 KiB
JavaScript
130 lines
2.7 KiB
JavaScript
var recordingLength = 0,
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recordingBuffer = [],
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bits = 16,
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sampleRate = 0;
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this.addEventListener('message', function(e) {
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switch (e.data.cmd) {
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case 'init':
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init(e.data.sampleRate);
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break;
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case 'start':
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start();
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break;
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case 'stop':
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stop();
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break;
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case 'destroy':
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destroy();
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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 'exportBlob':
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exportBlob();
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break;
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}
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});
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function init(sr) {
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sampleRate = sr;
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}
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function start() {
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}
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function stop() {
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}
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function destroy() {
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recordingLength = 0;
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recordingBuffer = [];
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sampleRate = 0;
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}
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function record(buffer) {
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recordingBuffer.push(buffer);
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recordingLength += buffer.length;
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}
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function exportBlob() {
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var audioBlob = new Blob([encodeWAV(mergeBuffer(recordingBuffer, recordingLength))]);
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this.postMessage({ from: 'exportBlob', blob: audioBlob });
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}
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// HELPER FUNCTIONS
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function mergeBuffer(buf, len){
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var result = new Float32Array(len);
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var offset = 0;
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for (var i = 0; i < buf.length; i++){
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result.set(buf[i], offset);
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offset += buf[i].length;
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}
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return result;
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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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/* file length */
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view.setUint32(4, 32 + 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); /*STEREO*/
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view.setUint16(22, 1, true); /*MONO*/
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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); /*STEREO*/
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view.setUint32(28, sampleRate * 2, true); /*MONO*/
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/* block align (channel count * bytes per sample) */
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//view.setUint16(32, 4, true); /*STEREO*/
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view.setUint16(32, 2, true); /*MONO*/
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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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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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} |