Video stopped but Firefox continues produce high CPU load.
On Win7x64 I have Firefox 58.0.1 (x64) and Adobe Flash Player 28.0.0.137. On YouTube I start playing video and then stop it. But Firefox continues to load CPU as if video was not stopped. The CPU load drops only after the tab with the page is closed. I have tested this problem on several computers with quite different hardware architectures (and this works the same).
Opaite Mbohovái (5)
It seems, this problem is present only when "1-click YouTube video downloader" extension is enabled.
Did you disable that extension to see what happens then or if the problem keeps happening?
Yes, I have disabled that extension and it seems the problem disappeared. But currently I work on computer with more powerful CPU (than several days ago) and this problem is not so noticeable here. So, I'm not 100% sure. I will test this problem again on the computer with less powerful CPU later (a week or so). Still, I'm 90% sure that the problem is with that extension, because data of CPU load in task manager confirm this.
Now I have made some better mesurements on the more powerful computer and situation seems to be even more interesting. Yes, measurements confirm that the promlem is with "1-click YouTube video downloader". When it is enabled, video is played with substantially higher CPU load (approximately 2 times higher) than when the extension is disabled. After video is stopped, the CPU load is reduced, but not to zero, only 2 times approximately. So, after video is stopped CPU load remains high, but not as high as when video is played. I also noticed that CPU load drops close to zero when the tab with stopped YouTube video becomes inactive (so, in order to reduce the load, it sufficient just to make other tab active).
I checked this problem again on the computer with less powerful CPU. And results are the same. This is "1-click YouTube video downloader" extension that makes problems with high CPU load.