User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 Build Identifier: First go to https://demos.mozilla.org/en-US/, click "watch a video", when it start playing right click and choose "fullscreen", you will see how sluggish slow flickering going into fullscreen can be, the video even stop playing for two seconds just switching to fullscreen. then go to http://www.youtube.com/ choose a video to play (you might need going to http://www.youtube.com/html5 first to enable html5), then click "fullscreen" on the controler, you will see the video go to "fullscreen" very smoothly without any delay. You might argue it's not real fullscreen, wait a minute, just press F11(to best experience it set "browser.fullscreen.animateUp" to 0), you will see the video goes to real fullscreen also very smoothly (6.0 botched it, now only fixed in maximized mode". Why don't we utilize these two methods together to create a perfect fullscreen? now I would much rather click (press) twice than endure the sluggishness. Reproducible: Always

Actually not any video has html5 mode, just try this one. http://www.youtube.com/watch?v=wm5pXe3nIXA&feature=topvideos_music

see bug 636411 comment 3

(In reply to comment #2) > see bug 636411 comment 3 > > *** This bug has been marked as a duplicate of bug 545812 *** This is bug 636411 comment 3: "They override our "Full Screen" right-click context menu, and until the Full Screen API is supported in Firefox, there's no way for them to provide that via a button." Actually I was complaining is that"our Full-Screen right-click" is too sluggish, Im content (by comparison) with youtube, although I need click twice.

It is sluggish. Right now it creates a clone of the video and seeks the clone to the original video's playback position before resuming playback. This is going to be fixed by implementing bug 545812, which will allow the original video (and whatever additional elements the page author desires) to become fullscreen directly. When that bug is fixed, the right-click fullscreen option will be modified to use the same code, solving the problem you're reporting.