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How is the resolution of a 720p/1080p video handled on a 4K display with display mode switching on?

PottypotsworthPottypotsworth Posts: 150Members, Plex Pass Plex Pass

Hi all,

I'm trying to understand what exactly happens with display mode switching when it is turned on in PMP and the computer resolution is set to 4K.

I have Display Mode switching set to on and when a 720p video starts i can see the info overlay shows the refresh rate has correctly changed to 23.975, but the actual resolution is 3840x2160p. In this case is Plex stretching the 720p video to fill the 4k screen? The TV also reports that it is receiving a 4K signal whilst the media is playing, despite the source video being 720p.

Many thanks

Best Answer


  • PottypotsworthPottypotsworth Posts: 150Members, Plex Pass Plex Pass

    Hi all,

    Apologies for bumping this, but this display mode switching is really confusing me. Is the whole point of it to ONLY switch to the right refresh/frame rate and keep the resolution the same as your desktop settings, or is it supposed to switch to the same resolution as the video file too? Trying to watch 720p content on a 4K TV with it all stretched out to 2160p looks awful. Is that by design, or is it an issue with my specific system not switching to the correct resolution despite always switching to the correct refresh/frame rate?


  • marshalleqmarshalleq Posts: 229Members, Plex Pass, TunerTester Plex Pass

    As I understand it, the display mode switching is entirely about refresh rate and fps. Basically getting something enabled that I used to call smooth video back in NVIDIA on Linux days. In those days (and probably still) Linux had a lot more capability than other platforms.

    The second part of your question is more interesting to me as it got me thinking. At first I assumed that this would be done on the software side in plex. Then I realised that it would send an actual signal of whatever it wanted (I recall when Kodi made their home screen display in 720p only so that it would speed up the menu navigation). When I switch mode to 720p on my TV, the TV detects it as 720p and acts accordingly. However, I am lucky enough to have a Plasma, where resolution is not an issue to switch between. On LCD/LED, the native resolution always looks better as they don't scale well. I think perhaps this might be the area of the problem, though I'm not sure. There used to be a check box in the settings which I never understood it's purpose of called 'Monitor is LCD' or similar. Perhaps this fixed resolution issues.

    I would definately hunt out the settings in your TV first, around detecting resolutions and do some digging around on that. I doubt (other than maybe the LED toggle) that Plex would scale a resolution in software, but could be wrong.

    Passionate about people, tech, photography, music, customer service, fitness and dabble at least a little in each ;)

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  • PottypotsworthPottypotsworth Posts: 150Members, Plex Pass Plex Pass

    Thank you both for the reply.

    Actually i have gone from a 55" 1080p Sony TV to a 65" 4K LG OLED so the size different isn't huge, it just seemed like the same 720p videos that i was used to on 1080p set look a lot more "fuzzy" when being displayed at 4K. Of course that is to be expected, but DVD content and other 720p/1080p content seems to be getting upscaled by the TV quite nicely.

    Actually, it is all moot at the moment. I switched the PC into 720p mode and i cannot for the life of me get the TV to now upscale the picture, it is simply sitting as a tiny box in the middle of the screen.

    I shall certainly try your test @altrus, when i can figure out the upscaling side of things :)

    I guess i figured that it would make more sense for Plex to (switch display mode on video start and) just send a 720p signal and let the TV sort it out, than it would to software scale that 720p image up to 4k and then (i assume) have the TV do nothing with the signal as it thinks it is 4k anyway. But that probably isn't even the case?

  • BrainSlugs83@gmail.comBrainSlugs83@gmail.com Posts: 1Members

    I know this is an old thread, but just to chime in, I'm having the same sorts of issues with 4K on plex. -- The 720P content looks awful. -- I had a 720P TV before, almost as big, and everything looked great, the video felt high quality. -- But the same content on a 4K TV, has massive banding and splotches and just looks terrible. -- Even on my large 1080p TV, the content looks fine, but in 4K, there's like 3 shades of black, and 4 tones for skin color and stuff in some scenes, and it's just the most terrible banding ever. -- Regular 4K video sources don't have that issue, but 720p streamed through the Plex app definitely does have the issue.

    It's just strange that the content can look great on a 1080p TV, and look terrible on a 2160p TV.

  • vlangvlang Posts: 1,648Members, Plex Pass, Plex Ninja Plex Ninja

    @BrainSlugs83@gmail.com do I understand it correctly that the TV is in 4K mode, but the video is 720p? Does any content look OK in 4K mode? (Maybe 1080p?) Is this with transcoding or directplay?

    Not at Plex anymore. I'm not a Ninja either.

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