waveform-playlist-nartj/lib/utils/exportWavWorker.js

Multiple track web audio editor and player with waveform preview

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = _default;

function _default() {
  var recLength = 0;
  var recBuffersL = [];
  var recBuffersR = [];
  var sampleRate;

  function init(config) {
    sampleRate = config.sampleRate;
  }

  function record(inputBuffer) {
    recBuffersL.push(inputBuffer[0]);
    recBuffersR.push(inputBuffer[1]);
    recLength += inputBuffer[0].length;
  }

  function writeString(view, offset, string) {
    for (var i = 0; i < string.length; i += 1) {
      view.setUint8(offset + i, string.charCodeAt(i));
    }
  }

  function floatTo16BitPCM(output, offset, input) {
    var writeOffset = offset;

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

  function encodeWAV(samples) {
    var mono = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : false;
    var buffer = new ArrayBuffer(44 + samples.length * 2);
    var view = new DataView(buffer);
    /* RIFF identifier */

    writeString(view, 0, 'RIFF');
    /* file length */

    view.setUint32(4, 32 + samples.length * 2, 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, 1, true);
    /* channel count */

    view.setUint16(22, mono ? 1 : 2, true);
    /* sample rate */

    view.setUint32(24, sampleRate, true);
    /* byte rate (sample rate * block align) */

    view.setUint32(28, sampleRate * 4, true);
    /* block align (channel count * bytes per sample) */

    view.setUint16(32, 4, true);
    /* bits per sample */

    view.setUint16(34, 16, true);
    /* data chunk identifier */

    writeString(view, 36, 'data');
    /* data chunk length */

    view.setUint32(40, samples.length * 2, true);
    floatTo16BitPCM(view, 44, samples);
    return view;
  }

  function mergeBuffers(recBuffers, length) {
    var result = new Float32Array(length);
    var offset = 0;

    for (var i = 0; i < recBuffers.length; i += 1) {
      result.set(recBuffers[i], offset);
      offset += recBuffers[i].length;
    }

    return result;
  }

  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 += 1] = inputL[inputIndex];
      result[index += 1] = inputR[inputIndex];
      inputIndex += 1;
    }

    return result;
  }

  function exportWAV(type) {
    var bufferL = mergeBuffers(recBuffersL, recLength);
    var bufferR = mergeBuffers(recBuffersR, recLength);
    var interleaved = interleave(bufferL, bufferR);
    var dataview = encodeWAV(interleaved);
    var audioBlob = new Blob([dataview], {
      type: type
    });
    postMessage(audioBlob);
  }

  function clear() {
    recLength = 0;
    recBuffersL = [];
    recBuffersR = [];
  }

  onmessage = function onmessage(e) {
    switch (e.data.command) {
      case 'init':
        {
          init(e.data.config);
          break;
        }

      case 'record':
        {
          record(e.data.buffer);
          break;
        }

      case 'exportWAV':
        {
          exportWAV(e.data.type);
          break;
        }

      case 'clear':
        {
          clear();
          break;
        }

      default:
        {
          throw new Error('Unknown export worker command');
        }
    }
  };
}