Firefox requires native OS support to play MP4 files with the HTML5 media player. On Windows XP this support is missing, so this won't work with Firefox.

You can try if the solution listed here still works for you.

• http://www.msfn.org/board/topic/175591-enable-mp4-h264-aac-html5-video-in-firefox-on-windows-xp-without-flash/

Hi cor-el. Thanks for your previous response. I got a bit lost with the size of your reference thread however have tried the following without success;

media.gmp-eme-adobe.forcevisible true media.gmp-eme-adobe.enabled true media.gmp.decoder.enabled true media.gmp.eme.enabled true

My plugins list includes Adobe flash v25.0.0.171 and OpenH264 Video Codec provided by Cisco Systems v1.6.

If I have missed a step please advise. Thanks.

OpenH264 Video Codec provided by Cisco Systems v1.6 is specifically for the Pocket feature, does nothing for HTML5 media files.

Try this Firefox 52 ESR: media.gmp-eme-adobe.enabled = true media.gmp-eme-adobe.forceSupported = true (49+) media.gmp-eme-adobe.forcevisible = true (only needed for 45-48) media.gmp-eme-adobe.visible = true (49+) media.gmp.decoder.enabled = true media.eme.enabled = true Modify media.gmp-manager.url : change %VERSION% to 51.0 (use 46.0 for Firefox 45)

For users of Firefox 52.xx ESR you need to remove the Primetime plugin if it is currently loaded. You can delete the gmp folders (gmp and gmp-gmpopenh264) in the profile folder.

• Help -> Troubleshooting Information -> Profile Directory: Windows: Show Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Change the %VERSION% part in media.gmp-manager.url to 51.0, otherwise Primetime plugin will not be loaded.

https://aus5.mozilla.org/update/3/GMP/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml

Change only the part in bold to 51.0 - just like:

https://aus5.mozilla.org/update/3/GMP/51.0/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/% OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml

I deactivated the Cisco plugin I mentioned previously and followed instructions then closed/opened FF but I have no Prime time codec loaded that I can see. What label will this have if it is loaded? I notice a new folder has been created gmp\WINNT_x86-msvc but it is empty. Any further suggestions appreciated.

Did you check out the last page(s) in the thread?

• http://www.msfn.org/board/topic/175591-enable-mp4-h264-aac-html5-video-in-firefox-on-windows-xp-without-flash/?page=9

For Firefox 52 ESR, see also:

• http://www.msfn.org/board/topic/175591-enable-mp4-h264-aac-html5-video-in-firefox-on-windows-xp-without-flash/?page=5#comment-1136465

If you still have problems then try to ask advice there.

You can try to use the Live Http Headers extension to see if you can catch the server response. Firefox would normally try to fetch/update the OpenH264 file if you toggle DRM off/on in "Options/Preferences -> Content".

I have reached the limit of my capabilities here. This article suggests prime time is no longer used? http://www.tec.tecno.id/news/Firefox-52:-Mozilla-disables-Adobe-Primetime-CDM-Plugin

That is article about the default in Firefox 52. That is why you need to set some prefs to true on the about:config page to enable this plugin.

Firefox should use the OpenH264 plugin with the pref changes proposed in the above posted article.

(thanks to all for input).

media.gmp-eme-adobe.visible true media.gmp-eme-adobe.enabled true https://aus5.mozilla.org/update/3/GMP/51.0/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml I reactivated Cisco H264 plugin and updated, the gmp\WINNT_x86-msvc is now occupied. I don't understand the Prime time plugin, it is not in my list.