Firefox mouse-over lag analyzed and workaround
Since it is not possible to create tickets without a premium account I am trying to get my information through here. Others have reported it before and I am experiencing the same issue: doing moving the mouse-pointer over a JWPlayer embedded video leads to serious lag and video dropouts (not audio). This does not happen with other Flash or HTML5 based players on this system, including both variants of Youtube.
The issue is *not* a direct problem of hovering the mouse over the player, it is a problem of the mouse-pointer being redrawn as a hand symbol when Firefox is having active focus (being the active foreground window). This means that there is no lag when Firefox is not having active focus, even though the player bar still pops up with mouse-overs.
Lag/dropouts only happen once the Firefox window becomes the active foreground window, because then the mouse-pointer also changes to a hand symbol. The drawing of said hand shaped pointer seems to be what causes all the troubles. The severity varies with various web-sites, but one where can bring Firefox almost to a stop (and corresponding "want to stop scrip" message) is:
It's noteworthy that the longer you move the mouse-pointer over the video the longer it takes for Firefox to return to normal. And in the case of the linked site you can even see the mouse-pointer blinking on and off slowly as it seems to be redrawn.
None of the following measures helps to alleviate the problem:
- Turning off/on hardware acceleration for mouse-pointer drawing.
- Turning off/on hardware acceleration in Firefox.
- Using Adobe Flash uninstall tool to do a clean reinstallation of flash.
- Making sure that the GPU (AMD 6750M) is clocked to maximum clock speed and utilized.
It does not happen when the video is played back in fullscreen-mode, though, only when it's embedded/windowed on the site.
Turning off Adobe Flash Protected Mode!
Obviously that workaround cannot be the real solution, which is why I provided all the information here.