[Regression?] Aurora 18.0a2+ and WMP Extension 1.1

[MrX1980]

Hello
with Firefox Aurora 18.0a2 / Nightly 19.0a1 and WMP extension these MP4/H.264 files are not loading anymore.
Firefox Release (16.0.2) and Beta (17.0b6) are working fine.

"Your browser cannot play H.264 high profile/baseline content with the HTML5 video element.
The video could not be loaded, either because the server or network failed or because the format is not supported."

example:
http://ie.microsoft.com/testdrive/Graph ... fault.html

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:18.0) Gecko/18.0 Firefox/18.0
buildID = 20121117042012

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/19.0 Firefox/19.0
buildID = 20121118030713

Does someone know the reason or a bug entry for this ?
Is it a regression ?

Thanks

Update:
I found a second H.264/MP4 example website: http://www.quirksmode.org/html5/tests/video.html

[Zlip792]

I didn't try with Firefox 16 or 17 although I can confirm it, that HTML5 H.264 is not working with WMP extension installed on Nightly on given testcase.

[pal-moz]

did you read "Release Notes for Developers" on the site ?

[Alice0775]

I've filed:
[*]#812942 [Core:XPConnect]-"HTML5 Extension for Windows Media Player Firefox Plug-in" is no longer working after landing Bug 788914 [Win]