Software giant Microsoft seems to be doing a lot with its rivals lately. Yesterday it released Firefox browser add-on extending HTML5-based video on the company's Windows 7 OS.

HTML 5 is a rival for Redmond's Silverlight and Firefox is a rival for Internet Exploder. The plugin enables Firefox users to play H.264-encoded video on HTML5 by using built-in capabilities of Windows 7.

It is worthwhile pointing out that Microsoft seems a little more comfortable about HTML 5 lately leading many of us to wonder what Silverlight's future will be. Claudio Caldato, principal program manager for Microsoft's interoperability team, pointed out in a blog post that although Mozilla Firefox is a principal competitor to Microsoft's own browser, it is offering a Windows Media Player plugin for Firefox, for watching Windows Media content, Caldato said.

"This new plugin, known as the HTML5 Extension for Windows Media Player Firefox plugin, is available for download at no cost. It extends the functionality of the earlier plugin for Firefox and enables Web pages that that offer video in the H.264 format using standard W3C HTML5 to work in Firefox on Windows. Because H.264 video on the Web is so prevalent, this interoperability bridge is important for Firefox users who are Windows customers."

The extension parses HTML5 pages and replaces video tags with a call to the Windows Media Player plugin, enabling content to be played in the browser. Firefox in some cases might fail to play a video even if the add-on is correctly installed, because a page might use a call to canPlayType to determine if the browser can play H.264 content, Microsoft said in release notes for the extension.

"Typically the check is done either using createElement('video') or getElementsByTagName('video') and then call canPlayType('video'mp4'). In both cases, the call will return empty string even if the Add-on is installed and the browser could play H.264 videos," Microsoft said.