@dosy/wav

node-wav

Reader and Writer streams for Microsoft WAVE audio files

This module offers streams to help work with Microsoft WAVE files.

Installation

Install through npm:

$ npm install wav

Example

Here's how you would play a standard PCM WAVE file out of the speakers using node-wav and node-speaker:

var fs = require('fs');
var wav = require('wav');
var Speaker = require('speaker');

var file = fs.createReadStream('track01.wav');
var reader = new wav.Reader();

// the "format" event gets emitted at the end of the WAVE header
reader.on('format', function (format) {

  // the WAVE header is stripped from the output of the reader
  reader.pipe(new Speaker(format));
});

// pipe the WAVE file to the Reader instance
file.pipe(reader);

API

• Reader()
• Writer()
• FileWriter()

Reader()

The Reader class accepts a WAV audio file written to it and outputs the raw audio data with the WAV header stripped (most of the time, PCM audio data will be output, depending on the audioFormat property).

A "format" event gets emitted after the WAV header has been parsed.

Writer(options)

The Writer class accepts raw audio data written to it (only PCM audio data is currently supported), and outputs a WAV file with a valid WAVE header at the beginning specifying the formatting information of the audio stream.

Note that there's an interesting problem, because the WAVE header also specifies the total byte length of the audio data in the file, and there's no way that we can know this ahead of time. Therefore the WAVE header will contain a byte-length if 0 initially, which most WAVE decoders will know means to just read until EOF.

Optionally, if you are in a situation where you can seek back to the beginning of the destination of the WAVE file (like writing to a regular file, for example), then you may listen for the "header" event which will be emitted after all the data has been written, and you can go back and rewrite the new header with proper audio byte length into the beginning of the destination (though if your destination is a regular file, you should use the the FileWriter class instead).

Default options:

{
  "channels": 2,
  "sampleRate": 44100,
  "bitDepth": 16
}

FileWriter(path, options)

The FileWriter class is, essentially, a combination of fs.createWriteStream() and the above Writer() class, except it automatically corrects the header after the file is written. Options are passed to both Writer() and fs.createWriteStream().

Example usage with mic:

var FileWriter = require('wav').FileWriter;
var mic = require('mic'); // requires arecord or sox, see https://www.npmjs.com/package/mic

var micInstance = mic({
  rate: '16000',
  channels: '1',
  debug: true
});

var micInputStream = micInstance.getAudioStream();

var outputFileStream = new FileWriter('./test.wav', {
  sampleRate: 16000,
  channels: 1
});

micInputStream.pipe(outputFileStream);

micInstance.start();

setTimeout(function() {
  micInstance.stop();
}, 5000);