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Refresh rate switching also changes resolution (4K -> 1080p)

refresh rate resolution 4k 1080p

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#1 Pantalaimon OFFLINE  

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Posted 19 May 2018 - 07:04 PM

I have a problem playing 4K content on my nVidia Shield / LG tv

 

The Shield and Emby app run in 4K resolution. I have 'Enable refresh rate switching' and 'Prefer exact refresh rate' both enabled in Emby.

Whenever I play 4K content, the refresh rate is changed as expected, but the resolution is changed from 2016p to 1080p. There is a 4K display mode available at the same refresh rate.

 

When I turn off 'Enable refresh rate switching', the content is displayed at 4K resolution, however the video becomes kind of choppy. When I turn it back on, the video is smooth as butter, but the resolution goes back to 1080p. The 'Prefer exact refresh rate' option is irrelevant here.

 

I've tried to change the resolution back to 4K at playtime in the display mode menu, but that seems to break HDR.

 

Anything I can do to have both smooth video AND 4k resolution?

 

 

 



#2 Jdiesel OFFLINE  

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Posted 19 May 2018 - 07:22 PM

This is by design. Your display has 3840x2160 pixels which are always active regardless of the source being used (480p, 720p, 1080p, 2160p, or anything else). When you have the system resolution set to 2160p and refreshrate switching disabled your Shield TV is sending a 2160p signal to your TV at all times. If you play a video that is anything other than your system resolution the Shield TV needs to convert the input video to the system resolution. The problem is that the Shield TV and most Android devices do a really poor job at this conversion. Most 4K TVs do a much better job at this because the are designed to accept a wide range of sourcea and and display them at the TVs native resolution (3840x2160). So when you play a 1080p video the Shield TV switches the output resolution to 1080p and let's the TV use its superior upscaler to convert the source video from 1080p to 2160p rather than the Shield TV doing the conversion.

Compare for yourself and see if you can tell the difference between a 720p or 1080p video played with the Shield TV outputting at 2160p versus the resolution of the source video. I'm willing to bet it looks better outputting at the source video resolution.

Edited by Jdiesel, 19 May 2018 - 07:25 PM.


#3 Pantalaimon OFFLINE  

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Posted 19 May 2018 - 07:41 PM


This is by design. Your display has 3840x2160 pixels which are always active regardless of the source being used (480p, 720p, 1080p, 2160p, or anything else). When you have the system resolution set to 2160p and refreshrate switching disabled your Shield TV is sending a 2160p signal to your TV at all times. If you play a video that is anything other than your system resolution the Shield TV needs to convert the input video to the system resolution. The problem is that the Shield TV and most Android devices do a really poor job at this conversion. Most 4K TVs do a much better job at this because the are designed to accept a wide range of sourcea and and display them at the TVs native resolution (3840x2160). So when you play a 1080p video the Shield TV switches the output resolution to 1080p and let's the TV use its superior upscaler to convert the source video from 1080p to 2160p rather than the Shield TV doing the conversion.
Compare for yourself and see if you can tell the difference between a 720p or 1080p video played with the Shield TV outputting at 2160p versus the resolution of the source video. I'm willing to bet it looks better outputting at the source video resolution.


That's just it; I'm not playing 1080p content, but 4k content, that gets downscaled to 1080p by the emby app now.

I agree that the output resolution should be closest to the source resolution and let the TV take care of the scaling. That's why I am surprised this doesn't work here for 4k content.
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#4 Jdiesel OFFLINE  

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Posted 19 May 2018 - 07:46 PM

I'd recommend sending an in app log replicating this so EBR can have a look. It's possible that something isn't being detected correctly.

#5 Jdiesel OFFLINE  

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Posted 19 May 2018 - 07:48 PM

Also what happens it you open the OSD during playback and switch to the resolution/refreshrate you think it should be using manually?

#6 ebr OFFLINE  

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Posted 19 May 2018 - 09:35 PM

Yeah, if we are switching to 1080 then it is because we think that is the video resolution.  Please provide details for a situation where you think this isn't working properly.

 

Thanks.



#7 Pantalaimon OFFLINE  

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Posted 20 May 2018 - 04:25 AM

Yeah, if we are switching to 1080 then it is because we think that is the video resolution. Please provide details for a situation where you think this isn't working properly.

Thanks.



5b012e35c5f91_1.jpg
 
Title screen; app runs in 2160p mode, movie is recognised as 4K
 
 
 5b012ec367830_2.jpg

 

Movie starts; display mode is set to 1080/23.98 after refresh rate switch.

 

 

5b012f08a14d8_3.jpg

 

TV OSD confirms resolution 1080p; Streaming info shows 4K video resolution

 

 

Also what happens it you open the OSD during playback and switch to the resolution/refreshrate you think it should be using manually?

 

Then the resolution/refresh rate is what it should be, however HDR stops working and the colors are washed out.



#8 iKryten OFFLINE  

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Posted 21 May 2018 - 01:37 AM

I can confirm this is happening to me also. And I also use an Nvidia Shield with an LG OLED TV. (Doesn't happen with Plex or Kodi, just the emby player.)



#9 ebr OFFLINE  

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Posted 21 May 2018 - 09:57 AM

If you open that display mode menu, is there an option for 4k at 23.97?



#10 Pantalaimon OFFLINE  

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Posted 21 May 2018 - 10:23 AM

If you open that display mode menu, is there an option for 4k at 23.97?

 

Yes there is:

 

5b02d650a527f_4.jpg



#11 iKryten OFFLINE  

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Posted 21 May 2018 - 11:00 AM

Yes there is:

 

5b02d650a527f_4.jpg

 

Ditto.



#12 xenu OFFLINE  

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Posted 21 May 2018 - 06:58 PM

I observed the same behavior using a Sony XE9305 I recently got: 4K content downscaled to 1080p, manually setting display mode to 4K loses HDR. Turning off refresh rate switching and content is displayed correctly.

Setup: NVIDIA Shield -> Denon X2400H  ->(ARC) Sony XE9305.



#13 ebr OFFLINE  

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Posted 22 May 2018 - 08:41 AM

Can you please follow the instructions to send a log from the app after starting playback for one of these?

 

Thanks.



#14 Pantalaimon OFFLINE  

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Posted 22 May 2018 - 11:59 AM

Can you please follow the instructions to send a log from the app after starting playback for one of these?

 

Thanks.

 

I've sent a log a minute ago.

 

I was playing the same video as in the screenshots; Ender's Game

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#15 ebr OFFLINE  

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Posted 22 May 2018 - 04:36 PM

Ah, okay.... Every movie this is happening with is a 2.35 aspect one, right?



#16 Pantalaimon OFFLINE  

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Posted 22 May 2018 - 05:08 PM

Ah, okay.... Every movie this is happening with is a 2.35 aspect one, right?

 

As a matter of fact, it is :blink:

 

I've found just one that is in a different format: 1.85 - this one plays at 2160p as it should, without issues :D



#17 ebr OFFLINE  

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Posted 22 May 2018 - 05:09 PM

Okay, thanks.  I'll look at fixing that.



#18 ebr OFFLINE  

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Posted 24 May 2018 - 01:00 PM

Please test with beta 1.5.91.

 

Thanks.







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