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4.1.3 • Public • Published

Node-style stream for getUserMedia

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If you just want to get some audio data from your microphone, this is what you're looking for!

Converts a MediaStream (from getUserMedia) into a standard Node.js-style stream for easy pipe()ing.

Note: This only works in a limited set of browsers (typically with with webpack or browserify), and then only for https or localhost in Chrome. It does not work in Node.js.


var getUserMedia = require('get-user-media-promise');
var MicrophoneStream = require('microphone-stream');
document.getElementById('my-start-button').onclick = function() {
  // note: for iOS Safari, the constructor must be called in response to a tap, or else the AudioContext will remain
  // suspended and will not provide any audio data.
  var micStream = new MicrophoneStream();
  getUserMedia({ video: false, audio: true })
    .then(function(stream) {
    }).catch(function(error) {
  // get Buffers (Essentially a Uint8Array DataView of the same Float32 values)
  micStream.on('data', function(chunk) {
    // Optionally convert the Buffer back into a Float32Array
    // (This actually just creates a new DataView - the underlying audio data is not copied or modified.)
    var raw = MicrophoneStream.toRaw(chunk)
    // note: if you set options.objectMode=true, the `data` event will output AudioBuffers instead of Buffers
  // or pipe it to another stream
  // It also emits a format event with various details (frequency, channels, etc)
  micStream.on('format', function(format) {
  // Stop when ready
  document.getElementById('my-stop-button').onclick = function() {


new MicrophoneStream(opts) -> Readable Stream

Where opts is an option object, with defaults:

  stream: null,
  objectMode: false,
  bufferSize: null,
  context: null
  • stream: MediaStream instance. For iOS compatibility, it is recommended that you create the MicrophoneStream instance in response to the tap - before you have a MediaStream, and then later call setStream() with the MediaStream.

  • bufferSize: Possible values: null, 256, 512, 1024, 2048, 4096, 8192, 16384. From Mozilla's Docs:

It is recommended for authors to not specify this buffer size and allow the implementation to pick a good buffer size to balance between latency and audio quality.

  • objectMode: if true, stream enters objectMode and emits AudioBuffers instead of Buffers. This has implications for pipe()'ing to other streams.

  • context is the AudioContext instance. If omitted, one will be created automatically.


Set the mediaStream, necessary for iOS 11 support where the underlying AudioContext must be resumed in response to a user tap, but the the mediaStream won't be available until later. Note: Some versions of Firefox leave the recording icon in place after recording has stopped.


Stops the recording. Note: Some versions of Firefox leave the recording icon in place after recording has stopped.

Event: data

Emits either a Buffer with raw 32-bit Floating point audio data, or if objectMode is set, an AudioBuffer containing the data + some metadata.

Event: format

One-time event with details of the audio format. Example:

  channels: 1,
  bitDepth: 32,
  sampleRate: 48000,
  signed: true,
  float: true

MicrophoneStream.toRaw(Buffer) -> Float32Array

Converts a Buffer (from a data event or from calling .read()) back to the original Float32Array DataView format. (The underlying audio data is not copied or modified.)


npm i microphone-stream

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