MediaRecorder.MediaRecorder()

The MediaRecorder() constructor creates a new MediaRecorder object that will record a specified MediaStream.

Syntax

var mediaRecorder = new MediaRecorder(stream[, options]);

Parameters

stream

The MediaStream that will be recorded. This source media can come from a stream created using navigator.mediaDevices.getUserMedia() or from an <audio>, <video> or <canvas> element.

options Optional

A dictionary object that can contain the following properties:

• mimeType: The mime type you want to use as the recording container for the new MediaRecorder. Applications can check in advance if this mimeType is supported by the user agent by calling MediaRecorder.isTypeSupported().
• audioBitsPerSecond: The chosen bitrate for the audio component of the media.
• videoBitsPerSecond: The chosen bitrate for the video component of the media.
• bitsPerSecond: The chosen bitrate for the audio and video components of the media. This can be specified instead of the above two properties. If this is specified along with one or the other of the above properties, this will be used for the one that isn't specified.

If bits per second values are not specified for video and/or audio, the default adopted for video is 2.5Mbps, while the audio default is adaptive, depending upon the sample rate and the number of channels.

Example

This example shows how to create a media recorder for a specified stream, whose audio bit rate is set to 128Kbit/sec and whose video bit rate is set to 2.5 Mbit/sec. The recorded media data will be stored in an MP4 wrapper (so if you gather the chunks of media data and save them to disk, they will be in an MP4 file).

...

if (navigator.mediaDevices.getUserMedia) {
  var constraints = { audio: true, video: true };
  var chunks = [];
  var onSuccess = function(stream) {
    var options = {
      audioBitsPerSecond : 128000,
      videoBitsPerSecond : 2500000,
      mimeType : 'video/mp4'
    }
    var mediaRecorder = new MediaRecorder(stream,options);
    m = mediaRecorder;
...

Specifications

Browser compatibility

[1] The initial Firefox OS implementation only supported audio recording.

See also

• Using the MediaRecorder API
• Web Dictaphone: MediaRecorder + getUserMedia + Web Audio API visualization demo, by Chris Mills (source on Github.)
• simpl.info MediaStream Recording demo, by Sam Dutton.
• Navigator.mediaDevices.getUserMedia()