Convert Audio Chunk to Audio PCM and Convert Audio PCM to Audio Base64 Data

audio_to_pcm.js

/**
 * Convert Audio Chunk to Audio PCM 16Bit 24kHz Mono
 * (Required audio/wav and 24kHz Mono)
 *
 * @param {Float32Array<ArrayBufferLike>} chunk
 * @returns {Int16Array<ArrayBuffer>}
 */
const chunkToPCM = function (chunk) {
 const minimalInt = 0x8000;
 const maximalInt = 0x7fff;
 const output = new Int16Array(chunk.length);
 for (let index = 0; index < chunk.length; index++) {
  const currentChunk = chunk[index];
  const clamping = Math.max(-1, Math.min(1, currentChunk));
  output[index] = clamping < 0 ? clamping * minimalInt : clamping * maximalInt;
 }
 return output;
};

/**
 * Convert Audio PCM to Audio Base64 Data
 *
 * @param {Int16Array<ArrayBuffer>} pcm
 * @returns {string}
 */
const PCMToBase64 = function (pcm) {
 let output = "";
 const byteArray = new Uint8Array(pcm.buffer);
 for (let index = 0; index < byteArray.length; index++) {
  const currentByte = byteArray[index];
  output += String.fromCharCode(currentByte);
 }
 return window.btoa(output);
};