We previously released a prototype implementation of the audio portion of a working draft of the W3C Media Capture API on HTML5 Labs. This prototype publicized some proposed API enhancements described in section 6.1 of Microsoft's HTML Speech XG Speech API Proposal.
In order to provide implementation experience and give Web developers early access to these work-in-progress APIs, we continue to evolve this prototype and are now publishing a second update.
Back in December, we updated the prototype to include image and video capture features to support scenarios we've heard are important for Web developers, as well as incorporating your feedback on audio.
This time we are specifically adding support for a version of the getUserMedia method, the MediaStream interface and its associated events and callbacks. getUserMedia allows developers to suggest what specific capture devices are desired. This then allows end users to authorize the browser to access the device they selected for the duration of the capture session. To learn more about the prototype and its objectives, you can read the IE blog post: "Media Capture Prototype: Improved Support for Real World Web Apps".
Install the prototype, open the samples in IE and see how users will be able to authorize the usage of media devices and choose between several similar capture peripherals. You can then dive into the samples code and see how getUserMedia is used.