Media/getUserMedia

getUserMedia

Goal

• Define and implement navigator.mediaDevices.getUserMedia() and associated functions with the W3C's WebRTC WG and Media Capture Task Force
• Spec is at Candidate Recommendation. Current editor's draft: W3 getUserMedia Editor's Draft.
• Scenarios: W3 MediaStream Capture Scenarios

Status

• Implemented getUserMedia on Desktop (Windows, Mac and Linux), Android, and B2G. Enabled in FF20+.
• Implemented new and old API as of FF36:
  • navigator.mediaDevices.getUserMedia - modern promise-returning version (unprefixed).
  • navigator.mozGetUserMedia() - legacy backwards-compatible version (prefixed).
• Capture resolution can be controlled with standard constraints for width, height, frameRate and (on mobile) facingMode can be used to choose between front/back camera. Supported in FF32+.
• Promise-based mediaDevices.getUserMedia API is supported in FF36+.
• Full constraints syntax with plain values and ideal-algorithm supported in FF38+.
• Input device enumeration through mediaDevices.enumerateDevices() is supported in FF39+.
• Can be turned off by setting media.navigator.enabled and media.peerconnection.enabled to false.
• Permissions UI is supported, allowing selecting devices or rejecting permission, with notifications that a tab is using a mic or camera, and a global indicator on the desktop to locate tabs using mics/cameras.
• Persistent permissions are supported.
• Explicit revocation of permission is supported.
• Supports multiple tabs getting data from the same mic or camera (if the user allows)
• Audio rate is fixed at 16000Hz.
• Echo cancellation is on by default, but connecting a captured audio stream directly to an audio element on the same system may still cause feedback unless a headset is used.
• Limited screen-sharing support under a pref.

Examples

• See mediaDevices.getUserMedia on developer.mozilla.org for examples.

Demos

• See WebRTC demos including mozGetUserMedia

Differences from Chrome webkitGetUserMedia()

Includes, but not limited to:

• Name :-)
• Firefox does not support Chrome's outdated constraints syntax ('mandatory', 'minWidth' etc.)
• Firefox does not support MediaStreamTrack.getSources(), an outdated version of enumerateDevices.
• Firefox leaves the mic/camera active (light on, etc) until the application explicitly calls mediastream.stop(). Chrome turns them on when assigned to a media element or PeerConnection, and off again when removed.
  • Note that if an application drops all references to a MediaStream but does not call stop(), the camera will remain active for some period of time (or until you navigate to another page in the tab or close the tab).
  • This behavior may change in the future
• Both now support window.URL.createObjectURL(stream), though Mozilla recommends against using it unless you have to. We expect Chrome to support srcObject = stream soon (perhaps prefixed as we are currently)
• Use the adapter.js shim to bridge cross-browser differences (constraints polyfill should be forthcoming).

Todo

• mediaDevices.getSupportedConstraints().
• More constraints to implement, like deviceId.