@excaliburjs/plugin-jsfxr/src/riffwave.mjs

excalibur-jsfxr provides sound effect generation utilizing a wrapper around jsfxr

/*
 * RIFFWAVE.js v0.03 - Audio encoder for HTML5 <audio> elements.
 * Copyleft 2011 by Pedro Ladaria <pedro.ladaria at Gmail dot com>
 *
 * Public Domain
 *
 * Changelog:
 *
 * 0.01 - First release
 * 0.02 - New faster base64 encoding
 * 0.03 - Support for 16bit samples
 *
 * Notes:
 *
 * 8 bit data is unsigned: 0..255
 * 16 bit data is signed: -32,768..32,767
 *
 */

let FastBase64 = {
  chars: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
  encLookup: [],

  Init: function () {
    for (var i = 0; i < 4096; i++) {
      this.encLookup[i] = this.chars[i >> 6] + this.chars[i & 0x3f];
    }
  },

  Encode: function (src) {
    var len = src.length;
    var dst = "";
    var i = 0;
    while (len > 2) {
      let n = (src[i] << 16) | (src[i + 1] << 8) | src[i + 2];
      dst += this.encLookup[n >> 12] + this.encLookup[n & 0xfff];
      len -= 3;
      i += 3;
    }
    if (len > 0) {
      var n1 = (src[i] & 0xfc) >> 2;
      var n2 = (src[i] & 0x03) << 4;
      if (len > 1) n2 |= (src[++i] & 0xf0) >> 4;
      dst += this.chars[n1];
      dst += this.chars[n2];
      if (len == 2) {
        var n3 = (src[i++] & 0x0f) << 2;
        n3 |= (src[i] & 0xc0) >> 6;
        dst += this.chars[n3];
      }
      if (len == 1) dst += "=";
      dst += "=";
    }
    return dst;
  }, // end Encode
};

FastBase64.Init();
var RIFFWAVE;
export default RIFFWAVE = function (data) {
  this.data;
  this.wav;
  this.dataURI;

  this.data = []; // Array containing audio samples
  this.wav = []; // Array containing the generated wave file
  this.dataURI = ""; // http://en.wikipedia.org/wiki/Data_URI_scheme

  this.header = {
    // OFFS SIZE NOTES
    chunkId: [0x52, 0x49, 0x46, 0x46], // 0    4    "RIFF" = 0x52494646
    chunkSize: 0, // 4    4    36+SubChunk2Size = 4+(8+SubChunk1Size)+(8+SubChunk2Size)
    format: [0x57, 0x41, 0x56, 0x45], // 8    4    "WAVE" = 0x57415645
    subChunk1Id: [0x66, 0x6d, 0x74, 0x20], // 12   4    "fmt " = 0x666d7420
    subChunk1Size: 16, // 16   4    16 for PCM
    audioFormat: 1, // 20   2    PCM = 1
    numChannels: 1, // 22   2    Mono = 1, Stereo = 2...
    sampleRate: 8000, // 24   4    8000, 44100...
    byteRate: 0, // 28   4    SampleRate*NumChannels*BitsPerSample/8
    blockAlign: 0, // 32   2    NumChannels*BitsPerSample/8
    bitsPerSample: 8, // 34   2    8 bits = 8, 16 bits = 16
    subChunk2Id: [0x64, 0x61, 0x74, 0x61], // 36   4    "data" = 0x64617461
    subChunk2Size: 0, // 40   4    data size = NumSamples*NumChannels*BitsPerSample/8
  };

  function u32ToArray(i) {
    return [i & 0xff, (i >> 8) & 0xff, (i >> 16) & 0xff, (i >> 24) & 0xff];
  }

  function u16ToArray(i) {
    return [i & 0xff, (i >> 8) & 0xff];
  }

  function split16bitArray(data) {
    var r = [];
    var j = 0;
    var len = data.length;
    for (var i = 0; i < len; i++) {
      r[j++] = data[i] & 0xff;
      r[j++] = (data[i] >> 8) & 0xff;
    }
    return r;
  }

  this.Make = function (data) {
    if (data instanceof Array) this.data = data;
    this.header.byteRate = (this.header.sampleRate * this.header.numChannels * this.header.bitsPerSample) >> 3;
    this.header.blockAlign = (this.header.numChannels * this.header.bitsPerSample) >> 3;
    this.header.subChunk2Size = this.data.length;
    this.header.chunkSize = 36 + this.header.subChunk2Size;

    this.wav = this.header.chunkId.concat(
      u32ToArray(this.header.chunkSize),
      this.header.format,
      this.header.subChunk1Id,
      u32ToArray(this.header.subChunk1Size),
      u16ToArray(this.header.audioFormat),
      u16ToArray(this.header.numChannels),
      u32ToArray(this.header.sampleRate),
      u32ToArray(this.header.byteRate),
      u16ToArray(this.header.blockAlign),
      u16ToArray(this.header.bitsPerSample),
      this.header.subChunk2Id,
      u32ToArray(this.header.subChunk2Size),
      this.data
    );
    this.dataURI = "data:audio/wav;base64," + FastBase64.Encode(this.wav);
  };

  if (data instanceof Array) this.Make(data);
}; // end RIFFWAVE