uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.4 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

thanks for replay i'll do and tell you what happen thanks

nothing change only buffer 5 min but ie buffer whole video

How are you verify the buffer and or latency of the video?

WestEnd said

How are you verify the buffer and or latency of the video?

ie11 i play the videos on qua. 360p and wait about 4 min. in IE11 after this 4 min. whole video bufferd.

firefox play same videos on same qua. 360p and wait more than 10 min. firefox only buffer 7 min. max

Without any links no one can test or verify what your saying here?