decode_eii.js

const fs = require("fs").promises;
const FileWriter = require("wav").FileWriter;

const muLawDecompressTable = [
  32124,
  31100,
  30076,
  29052,
  28028,
  27004,
  25980,
  24956,
  23932,
  22908,
  21884,
  20860,
  19836,
  18812,
  17788,
  16764,
  15996,
  15484,
  14972,
  14460,
  13948,
  13436,
  12924,
  12412,
  11900,
  11388,
  10876,
  10364,
  9852,
  9340,
  8828,
  8316,
  7932,
  7676,
  7420,
  7164,
  6908,
  6652,
  6396,
  6140,
  5884,
  5628,
  5372,
  5116,
  4860,
  4604,
  4348,
  4092,
  3900,
  3772,
  3644,
  3516,
  3388,
  3260,
  3132,
  3004,
  2876,
  2748,
  2620,
  2492,
  2364,
  2236,
  2108,
  1980,
  1884,
  1820,
  1756,
  1692,
  1628,
  1564,
  1500,
  1436,
  1372,
  1308,
  1244,
  1180,
  1116,
  1052,
  988,
  924,
  876,
  844,
  812,
  780,
  748,
  716,
  684,
  652,
  620,
  588,
  556,
  524,
  492,
  460,
  428,
  396,
  372,
  356,
  340,
  324,
  308,
  292,
  276,
  260,
  244,
  228,
  212,
  196,
  180,
  164,
  148,
  132,
  120,
  112,
  104,
  96,
  88,
  80,
  72,
  64,
  56,
  48,
  40,
  32,
  24,
  16,
  8,
  1,
];

const paths = [
  // `/Library/Arturia/Samples/Emulator II V/Factory/08 Cello & Violin/`,
  // `/Library/Arturia/Samples/Emulator II V/Factory/09 Orchestra Tune/`,
  // `/Library/Arturia/Samples/Emulator II V/Factory/10 Stacked Strings/`,
  // `/Library/Arturia/Samples/Emulator II V/Factory/11 Acoustic Guitar/`,
  `/Library/Arturia/Samples/Emulator II V/Factory/12 Voices/`,
  // `/Library/Arturia/Samples/Emulator II V/Factory/22 Loon Garden/`,
];

async function readPaths(path) {
  const paths = await fs.readdir(path);
  return paths.map((f) => path + f);
}

async function main() {
  const fileNames = (await Promise.all(paths.map((p) => fs.readdir(p)))).flat();
  const files = (await Promise.all(paths.map(readPaths))).flat();
  const fileBuffers = await Promise.all(files.map((file) => fs.readFile(file)));

  const parsed = fileBuffers.map((buf, i) => ({
    name: fileNames[i],
    flags: buf.readInt32LE(0).toString(16),
    length: buf.readInt32LE(4),
    loopStart: buf.readInt32LE(8),
    loopEnd: buf.readInt32LE(12),
    midiNote: buf.readUInt32LE(16).toString(16),
    waveData: buf.subarray(20),
  }));
  console.log(parsed);

  parsed.forEach((curr) => {
    const writer = new FileWriter(`output/${curr.name}.wav`, {
      sampleRate: 27777,
      channels: 1,
      bitDepth: 16,
      format: 1,
    });

    const buff = Buffer.alloc(curr.length * 2);
    curr.waveData.forEach((d, i) => {
      buff.writeInt16LE(
        muLawDecompressTable[(255 - d) % 128] * Math.sign(d - 128),
        i * 2
      );
    });
    writer.write(buff);
  });
}
main();