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Videos no longer streaming

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Something changed and I don't know what.

For some reason, I suddenly can't watch mp4 videos as they download.

I checked my Options | Applications for MP4 files and the default was changed to Quicktime (but I did not install or update anything from Apple.) I don't remember what my previous plugin was (it was connected to the "MPC Media Player" package), but it definitely wasn't QT or WMP.

QT has a documented problem streaming video within Firefox. Setting WMP as the default player likewise tries to download the entire file before playing. I have tried adjusting the streaming settings of both players, but nothing I do makes a difference.

I have a fast 5Mbps DSL connection. The problem is not my player or connection. It's the plug-in associated with MP4 (others?) files.

How do I fix this? Thx.

Something changed and I don't know what. For some reason, I suddenly can't watch mp4 videos as they download. I checked my Options | Applications for MP4 files and the default was changed to Quicktime (but I did not install or update anything from Apple.) I don't remember what my previous plugin was (it was connected to the "MPC Media Player" package), but it definitely wasn't QT or WMP. QT has a documented problem streaming video within Firefox. Setting WMP as the default player likewise tries to download the entire file before playing. I have tried adjusting the streaming settings of both players, but nothing I do makes a difference. I have a fast 5Mbps DSL connection. The problem is not my player or connection. It's the plug-in associated with MP4 (others?) files. How do I fix this? Thx.

All Replies (5)

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Many site issues can be caused by corrupt cookies or cache.

  • Clear the Cache and
  • Remove Cookies
    Warning ! ! This will log you out of sites you're logged in to.

Type about:preferences<Enter> in the address bar.

  • Cookies; Select Privacy. Under History, select Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.
  • Cache; Select Advanced > Network. Across from Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

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If you ope a file in an external program (media player) then Firefox will always download the full file before passing it to the player unless the file is a playlist file and not the actual media file. To play the file within Firefox you would have to have a plugin that supports the MIME type or file extension.

Firefox can also use the built-in HTML5 media player to play MP4 files provided that there is support on the OS level.


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Thanks for the replies.

I'm not sure why Firefox suddenly stopped playing MP4 files, and I wish I knew what app/plugin/etc was associated with mp4 files before. Now my only choices are WMP and Quicktime.

I tried reinstalling my preferred media player ("Media Player Classic") but it didn't help. Neither did reapplying my file associations from within the program (yes, I closed & reopened Firefox.)

I also tried toggling some obscure key in the "about:config" as recommended on Bugzilla, but it didn't help.

MSIE likewise also tries to download MP4 files rather than play them internally (not sure if this is new or not since I never use IE), so the problem almost certainly has nothing to do with cookies (and I use a ram cache.)

I'm running 64bit Win7. Firefox 34.0.5 (the latest version). I have no idea what program may have altered (I suspect) my MIME types.

Any ideas? Thx.

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Is Windows Media Foundation support enabled?

  • media.directshow.enabled = true
  • media.windows-media-foundation.enabled = true

Any error messages in the Web Console (Firefox/Tools > Web Developer)?

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Thanks for the reply cor-el.

"Yes" to both keys. "No" on error messages. :(