For what reason can video lag at a screen resolution of 3840x2160?

Question

Google Chrome

In general, the problem is that in the Chrome browser (of course, the latest version) on some sites, if you watch a video at a screen resolution of 3840x2160, it starts to lag (repeats some frames twice), for example, if you lower the resolution to 2048x1152, the lags disappear. There are lags both in the html5 player and in the flash player. For example, on the amvnews html5 site, the player is buggy, but the flash is not. But on the site gidonlin flash is buggy.
I did not notice such a problem in Explorer 11. No other browsers installed.
The actual characteristics of the laptop Lenovo y50-70:

• Processor: Core i7 4720HQ 2.6-3.6 GHz;
  
• Video: Nvidia GTX 960m 4GB;
  
• SSHD: 1TB HDD + 8GB SSD;
  
• Windows: Windows 8.1
  

P.S. All drivers are up to date, as is the flash player.

Answer 1

It seems that you need to watch which video card is used while watching the video. Perhaps the Intel HD Graphics 4600 is the default for "non-3D" and can't handle higher resolutions. I have no other suggestions.