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YouTube video in full screen freezes
I am playing YouTube video using Firefox v48.0.1 with Flash v220.127.116.11 (The same problem exists in old versions of Firefox and Flash too) in Windows (with Intel HD Graphics). I can reproduce it with following steps. 1. Go to YouTube webpage 2. Middle-mouse click on a video to send it to a new tab in background 3. Click to switch to the new tab 4. Double-click the video to view it in full screen 5. Around 30 seconds, there are three results happening in random
a. the video in "full screen" freezes (I need to kill flash exe in task manager) b. the video in "full screen" gets back to non-full screen c. the video loses focus while YouTube webpage gets focus (i.e. full screen video in background, YouTube webpage on top) (can see this case when Firefox window is not maximized)
As seen above, it seems that YouTube webpage is trying to get focus around 30 seconds. Between step 3 and 4 above, if I reload the webpage before going full screen, the problem does not occur. If I eliminate step 2 and 3 above and directly left-mouse click on a video in YouTube webpage (i.e. not send to background new tab), the problem does not occur.
If you are using Windows 7 or above, YouTube may use HTML5 instead of Flash to play video. You can use UAControl addon to set user agent to v36 or below so that YouTube can play with Flash. HTML5 is not good in Firefox with sluggish video playback. Some YouTube 1080p/4k/8k videos are not allowed using HTML5 (cannot see those 1080p/4k/8k formats for selection) while Flash can be played.