A Closer Look at the Microsoft h.264 Extension for Chrome

Today I took a closer look at how the “Windows Media Player HTML5 Extension for Chrome” works. To recap for a moment, Google announced that they are revoking native h.264 playback for the HTML5 <video/> tag in Chrome. A huge kerfuffle ensued. Yesterday, Microsoft announced that they were providing an extension to Chrome that provides h.264 support for the <video/> tag in Chrome on Windows 7.

I downloaded the CRX file and unzipped it. This is the contents:

PS> ls | select Length, Name | ft -AutoSize

Length Name
------ ----
  6540 contentscript.js
   678 manifest.json
163256 np-mswmp.dll
 59413 wmp eula.rtf
  3489 wmp releasenotes.txt
 28177 wmp128.png
   569 wmp16.png
  2233 wmp48.png

The np-mswmp.dll file looked familiar. And that is because it is the NSAPI plugin for Windows Media Player for Firefox.

ns-wmp

The remaining interesting file in the CRX is contentscript.js. In a nutshell, what this script does is look for <video/> elements that are referencing h.264 or WMV content and dynamically replace them with <object type=”application/x-ms-wmp” /> element referencing the same content.

Interesting Side-Effect

The Windows Media NSAPI plugin is installed into Chrome along with this extension which means any pages which explicitly embed the Windows Media Player will work.

wmpChrome

Also, this extension enables support for WindowsMedia Video content in <video/> elements.

var supportedMimeTypes = ['video/mp4', 'video/x-ms-wmv'];
var supportedVideoExtensions = ['.mp4', '.wmv', '.mp4v', '.m4v'];

Windows 7 Not Really Required

The Windows Media NSAPI plugin was released by the Port 25 group at Microsoft in April 2007. It doesn’t rely upon Windows 7 to work. The issue is just that Windows 7 is the first version of windows to ship with an h.264 codec for Windows Media Player. The extension should work on Windows XP and Vista if you have an h.264 codec for Windows Media, such as from the K-Lite codec pack.

Pointing the Way for Alternate Cross-Platform Implementations

This general approach also points the way for a 3rd party that has an NSAPI plugin that supports h.264 to extend Chrome (and Firefox) to support h.264 and whatever else the video player can support in the <video/> element. In particular it should be straightforward to create an extension that uses the VLC NSAPI plugin to extend the <video/> tag codec to support h.264 as well as DivX, QuickTime and MPEG-2.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: