Low quality, blocky cinematics

Hello. Ever since Lotv i've had low quality pre-rendered cinematics. The ones in hots and wol looked crips and HD, while these ones looks like i have a 320p video on full screen on a 1080p monitor (which i'm using).

The setting for movie quality in the options is set on high.

My specs: 64bit win 10, GTX 970, i5-4460, 8GB ram

What i've tried: Changing to full screen, windowed, etc. Still low quality.
64 bit and 32 bit clients, no difference.
Changing the video image and video color settings in the nvidia control panel.
The scan and repair feature in the battle.net client (i also do have the full game downloaded, i am not playing on optimal or something like that)
Installed k-lite codec pack just in case, i read that it might be a codec issue.

This issue has been driving me insane ever since the game came out. I've had to watch the cinematics on youtube which really annoys me because they don't really look as good there as they do ingame (for instance, when WOL or HOTS came out, the cinematics there were amazing, a lot better than on youtube, now youtube is miles ahead of the cinematics i watch)