Microsoft released on Wednesday a Firefox browser add-on extending HTML5-based video on the company's Windows 7 OS.

The plug-in enables Firefox users to play H.264-encoded video on HTML5 by using built-in capabilities of Windows 7, said Claudio Caldato, principal program manager for Microsoft's interoperability team, in a blog post. Mozilla Firefox is a principal competitor to Microsoft's own Internet Explorer browser.

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Microsoft has already been offering a Windows Media Player plug-in for Firefox, for watching Windows Media content, Caldato said. "This new plug-in, known as the HTML5 Extension for Windows Media Player Firefox plug-in, is available for download at no cost. It extends the functionality of the earlier plug-in 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."

HTML5 is an ongoing update to the HTML specification that adds capabilities for multimedia.

The extension is based on a Firefox add-on that parses HTML5 pages and replaces video tags with a call to the Windows Media Player plug-in, 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.

Also, the current version of the add-on uses Windows Media Player plug-in APIs to control video playback, thus creating differences between methods and properties defined in the HTML5 standard and those in the Windows Media Player plug-in. The company seeks to fix these limitations in the next edition of the add-on.

This article, "Microsoft boosts HTML5 video for Firefox on Windows 7," was originally published at InfoWorld.com. Follow the latest developments in business technology news and get a digest of the key stories each day in the InfoWorld Daily newsletter.