currently i use a wd black for my data and movies etc. when watching hd or higher material i get quite a lot artifacts and sometimes even a completely grey picture for 2-3 seconds. watching material from my ssd makes no problems.

now should i rather get a better hdd or aim for an ssd and which? i need 1-2 tb

u can watch 1080p movies from a USB external hdd or flashdrive, so ofc your hdd should be able to handle movie playback as sata speeds is much higher then usb

there is something wrong with your hdd, or the files, or the program u use...

u do NOT need ssd for movie storage and playback, hdd will be more then fine, and u will save alot of cash as 2tb of ssd will be expensive

its a wd black, crystaldisk says its fine. the player is vlc, newest version, the files are downloads from itunes/amazon/other platforms that offer hd/uhd material for sale.

dunno what is the problem.

pc is a almost new i5 8600 with gtx 1070ti 8gb and samsung evo 512gb as os partition and 2tb wd black as data partition.

Run HD Tune. Do an error scan, not the quick scan but a full one.
If that shows no damaged blocks then I'll believe the drive is fine.

Just because the source you've downloaded from is generally reliable source
that does not automatically imply that data corruption hasn't occurred.

Start with the scan and re-downloading the media and see if that fixing anything.

data runs fine when on ssd.

yea if the files works from the ssd then its not the problem, but what kinda files is it? .mp4? bitrate, resolution, fps, size?

and if u proberly scanned the hdd thats not the problem either

u mention u have the newest version of VLC, and i actually had some problems with that, take a look here: http://download.videolan.org/pub/videolan/vlc/ and try a version before 3.0

format is ts, codec hevc, 24fps, 15-55mbps, 10 bits

from 2 files i just randomly checked

And what does CrystalDiskMark show as the max. transfer speed of the WD black?

seq: 152,7
512k: 53,12
4k: 0,741
4k QD: 1,394