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Some mp4 videos don't play in Firefox using Windows Media Player.

  • 3 replies
  • 4 have this problem
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  • Last reply by Barry

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I'm using Firefox 49.0 on Windows XP Pro. I've installed the K-Lite Codec Pack 12.3.5 Basic, (http://www.free-codecs.com/K_Lite_Codec_Pack_download.htm), and now my Windows Media Player will play mp4 files. So will Chrome. But, on Firefox I get "Video format or MIME type is not supported."

I read the Mozilla article, "Play Windows Media files in Firefox with the Windows Media plugin", (https://support.mozilla.org/en-US/kb/play-windows-media-files-in-firefox), and installed the Windows Media Player Firefox Plugin from Interoperability Bridges and Labs Center, (http://www.interoperabilitybridges.com/windows-media-player-firefox-plugin-download). Now, the mp4 test at the end of that Mozilla article runs. But, I still get the "Video format or MIME type is not supported" on real websites, (http://www.cloudtownsend.com/video-advice/channel/Marriage/cloudT1046/).

My Explorer Files Type for MP4 is set to "Windows Media Player"; is there a "Windows Media Player Firefox Plugin" somewhere in the Program Files folder that I need to set it to?

All Replies (3)

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On Windows, Firefox uses the Media Foundation to decode H.264 / MP4 videos. Unfortunately, Microsoft never released the Media Foundation for Windows XP, so XP users historically have not been able to view videos on sites that use <video> tags without a "fallback" option for Flash or another plugin (Windows Media Player, VLC, etc.).

In another thread, a user said that one of the Mozilla-supplied plugins might help with this problem. I haven't explored it myself:

https://support.mozilla.org/questions/1135096#answer-909291

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I realize that's not a very satisfactory answer. You can try loading the video "stand alone" -- rather than embedded in the page -- to have a plugin jump in to play it. Alternately, you might want to download the video and play it in Windows Media Player, VLC, or another program that can handle the format. The attached screenshot illustrates where to find these options on the right-click context menu.

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Thank you, jscher2000, that was a quick response.

I had read that post, but want to stick with Media Player. The Play Windows Media files in Firefox with the Windows Media Player Plugin Mozilla support article says its possible. I'm hoping I just missed something, somewhere.

I can play MP4 videos from sites I bring up in Firefox by right clicking the blacked-out video box, and selecting "View Video" from the context menu. That causes XP to download the MP4 file, open Media Player in its own window, and play the video there. I'll do that if there's no other fix.

But, thanks for telling me about the Adobe possibility.

Added later...

Ummm... I've reread the Mozilla article. It was not that article that said it would make Media Player play mp4, it was another article on the web... the one that said to install the codec pack. (Sorry, I had the codec link wrong in my first post.)

I just thought that if Media Player can play mp4, (and, it can now, with the codec), and if Firefox can play Media Player, (and, it can now, with the plugin), that Firefox could use Media Player to play mp4. But, it won't. Unless I'm just missing a setting somewhere.

Modified by Barry