[SOLVED] Problem with video playback with 4K@60hz resolution

Dec 3, 2019
2
0
10
I’m using a Samsung UHD 55" RU8000 as my pc monitor. So far the it’s been good but I have encountered some issues and I was wondering if anyone else was experiencing this.

Whenever I set the resolution to 4k@60hz I experience lots of stuttering/lag and motion blurring when watching videos. Videos include playing video files and streaming off websites like Youtube and it affects all video resolutions that I have played whether I was playing a 720p, 1080p or a 4k video. If I change the resolution to 4k@30hz or 1440p@60hz/1080p@60hz/1080p@120hz it will play fine, the issue only exists when playing videos on 4k@60hz. Has anyone experienced this and know how to fix this?

The other issue I have is there’s no option to set the resolution at 1440p@120hz even the tv specs say it supports it. I’m only able to use 1080p@120hz. Has anyone actually been able to use 1440p@120hz on the RU8000?

My pc system:
Cpu: i7 4790K
Gpu: Nvidia GTX 760
Ram: 32GB
OS: Win7 64bit Pro
Connecting HDTV to gpu using a HDMI 2.0 cable
 
Solution
GTX 700 series does not have a video decoder powerful enough to handle 4K resolution. You will need a newer graphics card.

The GTX 760 only supports HDMI 1.4, which has a maximum of ≈75 Hz at 1440p. 120 Hz will not be possible without upgrading to an HDMI 2.0 card. 4K 60 Hz itself is only supported with chroma subsampling on GTX 700 series cards, for the same reason.
GTX 700 series does not have a video decoder powerful enough to handle 4K resolution. You will need a newer graphics card.

The GTX 760 only supports HDMI 1.4, which has a maximum of ≈75 Hz at 1440p. 120 Hz will not be possible without upgrading to an HDMI 2.0 card. 4K 60 Hz itself is only supported with chroma subsampling on GTX 700 series cards, for the same reason.
 
Solution
Dec 3, 2019
2
0
10
Ok that explains why there's no option for 1440p@120hz. What I don't understand is why I can't play videos smoothly on 4k@60hz screen resolution but it works on 4k@30hz screen resolution, the videos I'm playing are not 4K videos, most are 720p or 1080p. Even the videos I'm streaming on YT are 1080p, but I still experience the same lagging picture whether in full screen or windowed viewing, everything else is fine, there's no lagging in the audio.
 
Ok that explains why there's no option for 1440p@120hz. What I don't understand is why I can't play videos smoothly on 4k@60hz screen resolution but it works on 4k@30hz screen resolution, the videos I'm playing are not 4K videos, most are 720p or 1080p. Even the videos I'm streaming on YT are 1080p, but I still experience the same lagging picture whether in full screen or windowed viewing, everything else is fine, there's no lagging in the audio.
In order to play video, the video file needs to be decoded into uncompressed frames in real time. In general this is done by a dedicated video decoder circuit, which is built into the graphics card. The video decoder in the GTX 760 is not designed for 4K video files and cannot decode the video file quickly enough. This is strictly a limitation in decoding video files, which is a a separate process from generating your own 4K frames (i.e. games or desktop).

You can also try letting your CPU decode video ("software decoding") by disabling hardware acceleration in your video playback software, but it is likely your CPU will max out, which is why we have dedicated hardware to do this.

I had the same issues with 4K video playback when I had a 780 Ti.

EDIT: I'm not sure why 1080p or 720p video files would have trouble playing. I did not experience those issues. All I can really say is that the GTX 760 predates 4K screens and is really not designed for it :/