Question 4k movies lagging

[Mr-Shark]

Hi guys, so I've been having some issues regarding 4k movies and shows, videos in general.
I recently bought a new monitor as an upgrade AOC AG271QG, and when ever i try to play a movie in 4k it's choppy and lagging. So far i tried GOM player and built in player from win10, it's laggier in GOM.
My pc is 4-5 years old now: cpu i5 4690k, 16 gb ddr3, gpu msi 970 4k.
I know it's outdated, but i hoped it could still play 4k. Is the hardware the problem is am i missing something? Hdd is 10 000 rpm and with two SSD (didn't try to play movies from SSD
New pc will come eventually, to follow the upgrade of monitor.

Also will i be able to stream 4k from pc to oled c9 using plex

 

[Oussebon]

Were you able to play 4k movies okay on the old monitor?

Is the monitor connected to the graphics card or the motherboard?

Have you tried another piece of software like the free VLC?

Does Task Manager show high disk usage on idle / when playing the movie? If so, what processes are using the drive?

 

[Mr-Shark]

I didnt try playing 4k movies on older monitor, so can't compare them.

Monitor is connected to GPU, not motherboard.

I'll try different software and will monitor processes that are in background and post screenshot here.

 

[SkyNetRising]

when ever i try to play a movie in 4k it's choppy and lagging.

Try with MPC-HC video player.
https://mpc-hc.org/

 

[Mr-Shark]

Tried vlc, works perfectly.

Also streaming on Emby works great on webos on LG.
I had some buffering issues with Plex, even tho my connection speed is 150 Mbps and all cables are cat. 6 (the longest one is 20 m, other two are 1 and 2 m)

 

[Oussebon]

Are the 4k movies straight up untranscoded 4k BR rips?

The PC itself is acting as your plex server? Or is another device the server (if so, what)?

Do all devices on the network have gigabit ethernet ports? Including the LG TV? They're often only 100mbps.