I'm trying to convert a .wav file to a byte array string. I need to do this on the back-end targeting the file is being an issue.

        files.forEach(file => {
            let index = files.indexOf(file)
            let reader = new FileReader();
            reader.readAsArrayBuffer(file);
            console.log(reader.result);

            reader.onload = function (event) {
                let byteArray = new Uint8Array(reader.result);
                let FileName = file.name;
                let dataAsByteArrayString = byteArray.toString();
                var listHtml = $list.html();

The above code uses npm's filereader which says to target a file. I'm having difficulty doing this since this is not a front end drag and drop of the file.

my file that is generated is called "response.wav" how would I convert this file using JavaScript and node extensions? Thanks!

I'm trying to convert a .wav file to a byte array string. I need to do this on the back-end targeting the file is being an issue.

        files.forEach(file => {
            let index = files.indexOf(file)
            let reader = new FileReader();
            reader.readAsArrayBuffer(file);
            console.log(reader.result);

            reader.onload = function (event) {
                let byteArray = new Uint8Array(reader.result);
                let FileName = file.name;
                let dataAsByteArrayString = byteArray.toString();
                var listHtml = $list.html();

The above code uses npm's filereader which says to target a file. I'm having difficulty doing this since this is not a front end drag and drop of the file.

my file that is generated is called "response.wav" how would I convert this file using JavaScript and node extensions? Thanks!

• javascript
• node.js
• file-conversion

• Into a byte array string? – ccjmne Commented Mar 4, 2018 at 1:30
• Yes such as: DataAsByteArrayString':'82,73,70,70,255,255,255,255,87,65,86,69,102,109,116,32,16,0,0,0,1,0,1,0,34,86,0,0,68,172,0,0,2,0,16,0,76,73,83,84,26,0,0,0,73,78,70,79,73,83,70,84,14,0,0,0,76,97,118,102,53,55,46,55,49,46,49,48,48,0,100,9 – fengelhardt Commented Mar 4, 2018 at 1:34
• Are you trying to actually parse the WAV file, or do you just need to generically read a file? – Brad Commented Mar 4, 2018 at 1:43

2 Answers 2

I dont know if this will help but the last project I worked on we parsed a .wav file using the Node buffer API and wrote it using the Node file API. If you have more questions about the code I can direct you to the person that worked on this file the most. I hope it helps somewhat https://github./IntelliSound/intelliSound-Server/blob/development/lib/sound-data-parser.js

'use strict';

function ParsedWave(buffer) {
  
  const RIFF_HEADER_OFFSET = 0;
  const FILE_SIZE_OFFSET = 4;
  const RIFF_FORMAT_OFFSET = 8;
  const SUBCHUNK1_ID_OFFSET = 12;
  const AUDIO_FORMAT_OFFSET = 20;
  const NUMBER_OF_CHANNELS_OFFSET = 22;
  const SAMPLE_RATE_OFFSET = 24;
  const BITS_PER_SAMPLE_OFFSET = 34;
  const SUBCHUNK2_ID_OFFSET = 36;
  const SUBCHUNK2_SIZE_OFFSET = 40;
  const DATA_OFFSET = 44;
  
  this.buffer = buffer;
  this.riff = buffer.slice(RIFF_HEADER_OFFSET, RIFF_HEADER_OFFSET + 4).toString('utf8');
  this.fileSize = buffer.readUInt32LE(FILE_SIZE_OFFSET);
  this.riffType = buffer.slice(RIFF_FORMAT_OFFSET, RIFF_FORMAT_OFFSET + 4).toString('utf8');
  this.subChunk1Id = buffer.slice(SUBCHUNK1_ID_OFFSET, SUBCHUNK1_ID_OFFSET + 4).toString('utf8');
  this.audioFormat = buffer.readUInt16LE(AUDIO_FORMAT_OFFSET);
  this.numberOfChannels = buffer.readUInt16LE(NUMBER_OF_CHANNELS_OFFSET);
  this.sampleRate = buffer.readUInt32LE(SAMPLE_RATE_OFFSET);
  this.bitsPerSample = buffer.readUInt16LE(BITS_PER_SAMPLE_OFFSET);
  this.subChunk2Id = buffer.slice(SUBCHUNK2_ID_OFFSET, SUBCHUNK2_ID_OFFSET + 4).toString('utf8');
  this.subChunk2Size = buffer.readUInt32LE(SUBCHUNK2_SIZE_OFFSET);
  this.data = buffer.slice(DATA_OFFSET, this.subChunk2Size + DATA_OFFSET);
}

// Andrew - The bufferMapper function is going to accept a parsed wave-file and output
//          an array of values corresponding to the data subchunk in a format which can
//          be accepted as input to the neural network.

const bufferMapper = parsedWave => {
  
  const SIXTEEN_BIT_ZERO = 32768;
  const SIXTEEN_BIT_MAX = 65535;
  
  parsedWave.neuralArray = [];
  
  for (let i = 0; i < parsedWave.data.length; i += 2) {
    const sample = parsedWave.data.readInt16LE(i);
    const unsignedSample = sample + SIXTEEN_BIT_ZERO;
    const sigmoidSample = unsignedSample / SIXTEEN_BIT_MAX;
    parsedWave.neuralArray.push(sigmoidSample);
  }
  return parsedWave;
};

module.exports = data => {

  const parsedWaveFile = new ParsedWave(data);

  if (parsedWaveFile.riff !== 'RIFF') {
    throw new TypeError('incorrect file type, must be RIFF format');
  }

  if (parsedWaveFile.fileSize > 10000000) {
    throw new TypeError('file too large, please limit file size to less than 10MB');
  }

  if (parsedWaveFile.riffType !== 'WAVE') {
    throw new TypeError('file must be a WAVE');
  }

  if (parsedWaveFile.subChunk1Id !== 'fmt ') {
    throw new TypeError('the first subchunk must be fmt');
  }

  if (parsedWaveFile.audioFormat !== 1) {
    throw new TypeError('wave file must be unpressed linear PCM');
  }

  if (parsedWaveFile.numberOfChannels > 2) {
    throw new TypeError('wave file must have 2 or less channels');
  }

  if (parsedWaveFile.sampleRate > 48000) {
    throw new TypeError('wave file must have sample rate of less than 48k');
  }

  if (parsedWaveFile.bitsPerSample !== 16) {
    throw new TypeError(`file's bit depth must be 16`);
  }

  if (parsedWaveFile.subChunk2Id !== 'data') {
    throw new TypeError('subchunk 2 must be data');
  }

  const neuralMappedWaveFile = bufferMapper(parsedWaveFile);

  return neuralMappedWaveFile;
};

Using the included fs module, you can read in your wav file like so:

const fs = require('fs');
const path = './path/to/my.wav';

fs.readFile(path, (err, data) => {
    // Data is a Buffer object 

});

For documentation on working with a Node.JS Buffer see here. Now, if you were more interested in the file conversion portion, there are a couple of libraries out there. If you just need the conversion functionality, and not implementing yourself, node-fluent-ffmpeg may work for you. If you want to implement it yourself, this node-wav file may be a good reference (too much to paste here).

If you need to go from Buffer to ArrayBuffer, this SO shows some options.