Weeks after Google announced it would drop support for H.264-encoded video from Chrome, Microsoft announced it's adding support back in through a browser extension for Windows 7 users.

"Today, as part of the interoperability bridges work we do on this team, we are making available the Windows Media Player HTML5 Extension for Chrome, which is an extension for Google Chrome to enable Windows 7 customers who use Chrome to continue to play H.264 video," said Claudio Caldato, principal program manager on Microsoft's Interoperability Strategy Team, in a blog post. The software can be downloaded from MIcrosoft's Web site.

The move matches what Microsoft already did with Firefox, which unlike Chrome never supported H.264 in the first place. Mozilla, Google, and Opera prefer the WebM video-streaming technology and its VP8 video codec in particular, which at least for now doesn't require the patent royalty payments that H.264 does for browser makers and those offering for-fee video over the Net.

And the move also points a way through the video codec mess that currently prevails on the Web. Microsoft, and possibly Apple, could offer H.264 plug-ins for use by browsers that don't support it, and Google could offer WebM plug-ins for the opposite situation. Indeed, Microsoft said Google is working on such a plug-in for Internet Explorer on Windows.

That solution doesn't make life much easier for Web site operators trying to decide whether they need to support both technologies or just one, though, unless a large fraction of people install such a plug-in or unless the Web developer is willing to fall back to Adobe Systems' Flash Player.

A requirement to license patents--from a group called MPEG LA in the case of H.264 patents--is antithetical to the World Wide Web Consortium's ethos for open Web standards. "In order to promote the widest adoption of Web standards, W3C seeks to issue recommendations that can be implemented on a royalty-free (RF) basis. Subject to the conditions of this policy, W3C will not approve a recommendation if it is aware that essential claims exist which are not available on royalty-free terms," the W3C's patent policy states.

H.264, also called AVC (Advanced Video Coding) and MPEG-4 Part 10, definitely has patent issues. It's not yet clear how free WebM and VP8 are, though Mozilla expressed confidence and Google offered royalty-free use of VP8 technology it acquired when it bought On2 Technologies in 2010. MPEG LA, though, has a different view.

"We do not believe VP8 is patent free," the organization told CNET in a statement in late January. "There continues to be interest in the facilitation of a pool license to address the apparent marketplace desire for convenience in accessing essential VP8 patent rights owned by many different patent holders under a single license as an alternative to negotiating individual licenses."

The nascent HTML5 standard includes built-in video support in an attempt to make video as easy to use as, say, JPEG graphics on the Web today. But Google's move spotlighted a rift in the HTML5 standards world: because of differing views on the appropriate codec, neither H.264 nor VP8 nor any other codec is specified. And with Microsoft and Apple pushing one way and the other three browser makers pushing the other way, it doesn't look like there will be any resolution any time soon.

In a blog post today IE General Manager Dean Hachamovitch expounded on Microsoft's earlier position, mostly reiterating the company's concerns about the possibility of VP8 patent infringement and Microsoft's willingness to accommodate a WebM plug-in.

"The only true arbiter of infringement, once it's asserted, is a court of law," Hachamovitch said, suggesting one way Google could protect WebM users would be through an indemnification pledge to protect them in the event they're sued for patent infringement. "If Google were truly confident that the technology does not infringe and is not encumbered by patents whatsoever, wouldn't this indemnification be easy It's one way to move away from conversations about unknown and unbounded risk to a rational conversation about costs and liability."

Microsoft is one of the many patent holders whose H.264 patents are licensed by MPEG LA, and Hachamovitch had an offer for Google if it does offer indemnification:

Ultimately, Microsoft remains agnostic in terms of HTML5 video as long as there is clarity on the intellectual property issues. To make it clear that we are fully willing to participate in a resolution of these issues, Microsoft is willing to commit that we will never assert any patents on VP8 if Google will make a commitment to indemnify us and all other developers and customers who use VP8 in the future. We would only ask that we be able to use those patent rights if we are sued first by somebody else. If Google would prefer a patent pool approach, then we would also agree to join a patent pool for VP8 on reasonable licensing terms so long as Google joins the pool and is able to include all other major providers of playback software and devices. The entire industry benefits from a significant investment in an ecosystem around a format well insulated from legal issues. As JPEG taught the industry, profitable companies merely wishing IP issues away does not make those issues go away.

Google didn't immediately respond to a request for comment.

Google is working on a plug-in to bring WebM to Windows, and Microsoft is helping with that work, Hachamovitch added.

"Our support for H.264 results from our views about a robust Web and video ecosystem that provides a rich level of functionality, is the product of an open standards process like the W3C's HTML5 specification, and has been free from legal attacks. Microsoft is agnostic and impartial about the actual underlying video format for HTML5 video as long as this freedom continues," Hachamovitch said. "Our commitment to play WebM videos in IE9 for users who have installed WebM demonstrates our approach. We have worked closely with Google to help them deliver a WebM implementation on Windows and Google engineers are on the Microsoft campus this week' we appreciate their positive feedback to date around this work."

VP8 appears to deliberately sidestep H.264 patents, Carlo Daffara said in a blog post in January:

...It is clear that most design decisions in the original On2 encoder and decoder [which became VP8] were made to avoid preexisting patents...By going through the H.264 "essential patent list," however, I found that in the US (that has the highest number of covered patents) there are 164 non-expired patents, of which 31 specific to H264 advanced deblocking (not used in WebM), 34 related to CABAC/CAVAC not used in WebM, 16 on the specific bytecode stream syntax (substituted with Matroska), 45 specific to AVC. The remaining ones are (to a cursory reading) not overlapping with WebM specific technologies, at least as they are implemented in the libvpx library as released by Google (there is no guarantee that patented technologies are not added to external, third party implementations).

Further details are available in his earlier analysis.

Updated 8:33 a.m. PT with comment from MPEG LA and further details.