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YouTube HTML5 WebM playback seems broken in Firefox 4 Beta 7 and the current Firefox 4 nightlies

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  • 180 have this problem
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  • Last reply by UserFx51

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WebM playback on YouTube via the HTML5 player seems broken at present in Firefox 4 Beta 7 and the current Firefox 4 nightlies. I have beta 7 install on Win32 and Minefield on Linux x86-64, both without Flash installed and both have joined the HTML5 trial. When attempting to watch a video you currently just get the HTML5 player chrome with no WebM badge and just a black, videoless content pane where the video should be.

Opera 10.63, in contrast, still works fine. So it feels like YouTube is incorrectly detecting the user agent when Firefox 4 is used and as a consequence mistakenly deciding that it shouldn't serve WebM video in that instance. I've not yet tried setting Firefox 4's user agent string to, say, Opera 10.63. I'll try that next.

Can anyone confirm that they're seeing the same problem and is there any other workaround beyond changing the user agent string (presuming that works)?

WebM playback on YouTube via the HTML5 player seems broken at present in Firefox 4 Beta 7 and the current Firefox 4 nightlies. I have beta 7 install on Win32 and Minefield on Linux x86-64, both without Flash installed and both have joined the HTML5 trial. When attempting to watch a video you currently just get the HTML5 player chrome with no WebM badge and just a black, videoless content pane where the video should be. Opera 10.63, in contrast, still works fine. So it feels like YouTube is incorrectly detecting the user agent when Firefox 4 is used and as a consequence mistakenly deciding that it shouldn't serve WebM video in that instance. I've not yet tried setting Firefox 4's user agent string to, say, Opera 10.63. I'll try that next. Can anyone confirm that they're seeing the same problem and is there any other workaround beyond changing the user agent string (presuming that works)?

Chosen solution

See Bug 616252 – html5 video on youtube is broken (NS_ERROR_XPC_NOT_ENOUGH_ARGS from addEventListener)

(please do not comment in bug reports)

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All Replies (8)

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I set the user agent string to match Opera's using the UAControl add-on but it made no difference. Whatever change YouTube has made that's preventing Firefox 4 from working is apparently more subtle.

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Chosen Solution

See Bug 616252 – html5 video on youtube is broken (NS_ERROR_XPC_NOT_ENOUGH_ARGS from addEventListener)

(please do not comment in bug reports)

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Bummer. Okay, I'll just wait and see what happens.

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WebM playback is now working again on YouTube in the current Firefox 4 nightly. Possibly in Beta 7 as well but I've not tried it yet.

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Modified by cor-el

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After Adobe upgrade, YouTube still gives audio, but a blank white space where the video should be.

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Clear the cache and the cookies from sites that cause problems.

  • "Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"
  • "Remove the Cookies" from sites causing problems: Tools > Options > Privacy > Cookies: "Show Cookies"
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I just noticed that Firefox is playing some of my videos from youtube in WEBM format; That creates a huge problem for me because of distortion/Lag on ALL Webm videos with intense fast action scenes;I guess my onboard video card can not handle the demand of WEBM.

My computer is not too old or new either so I really am concern for the foreseeable future,Millions of people from around the world that can not afford new computers will be affected by this new tech.

This ruins everything for me because Firefox is my favorite browser I am forced to switch to Internet Explorer to watch sports videos in H264/Flash - I dont have a problem viewing videos with Flash or H264.