Why is 3D video from PC to LG smart TV much worse than from a flash drive?

Question

Video cards

Good afternoon! Tell me, please, what could be the problem:
There were problems with watching movies from a computer on a TV in 3D.
The same movie, when viewed from a computer, on the screen trembles, twitches, and when played from a flash drive, everything is OK.
Movie in Top Anamorphic Stereo, 3D mode on TV is on.
TV - LG 42LA660V
graphics card AMD Radeon 7700
Telecom HDMI to HDMI cable (19M -19M) ver.1.4b
connected in second monitor mode
Where to dig?