Enable Refresh Rate Switching - why?

[justinrh 260]

The Android TV app on my Shield has a playback setting of "Enable Refresh Rate Switching".  Why would I need this, what problem does it solve?  Is it for the sake of the sending device (Shield) or the output device (TV)?

[ALD76 26]

It is to eliminate judder. You might benefit from enabling it depending on your TV and your sensitivity to it

[ebr 16182]

Video screens refresh (show a new image) on a set schedule (frequency).  Usually (in the US) something close to 30 times per second or some multiple of that.  Video is shot at pretty much this same frame rate so that works out well.

However, film was typically shot at 24 frames per second.  Now you have 24 images per second but your monitor is showing 30 which means that some frames show for more than one refresh cycle and many frames are going to be late displaying because the timing doesn't match up.  Ever notice wide scenic pan shots in a movie seeming to skip every second or so?

So many TVs can change their refresh rate to match the frame rate of film to make the display smoother.   However, many TVs can apply various techniques to account for the mismatch as well such that you may or may not need to change the refresh rate.  One technique is using a refresh rate that is evenly divisible by both 30 and 24 such as 120Hz.

[justinrh 260]

My TV has judder and stutter settings.  Is it advisable to use the TV's settings over Emby's?

The problem I see a good bit from recorded TV is part of the scene will be blurry and not move at the same rate as a moving object, like a person walking.  The blurry part seems to move in waves.

I still don't understand where (or how) Emby is 'enabling' the switching.  Is Emby switching to the rate of the video, or is Emby telling the device (Shield?) to switch its rate to match the video?  Is this a dynamic switching (continuously adjusting and switching during the entire playback) or is it just a one time preference to whatever?

[ebr 16182]

What you describe doesn't sound like frame rate judges and it shouldn't be with recorded TV anyway. 

If you don't experience the judges, then I would leave the app setting off. 

[justinrh 260]

For some details:

 

But it would still be helpful for me to understand if my questions above were addressed.  It sounds like this 'enable switching' is another way of saying 'match video frame rate'.

[rbknox 6]

When I have Display Refresh Rate switching enabled, I encounter various issues:  during some TV (60 Hz) content the display will intermittently go black (and no audio) for 2-3 seconds at a time; less common but sometimes when starting to playback a recorded TV show it starts with black screen and eventually stabilizes.   The first issue is not unlike problems I had with Apple TV with frame rate matching turned on.  Apple TV is fixed now but the explanation was apparently some TVs (mine is early Samsung 4K) are not able to switch the display fast enough.   

I would just leave this switching turned off except that when I watch a movie (HD or UHD mkv), the refresh rate switches correctly to 24 Hz when switching is enabled.  With switching turned off, Stats for Nerds shows movies playing at 60 Hz.

I would rather not have to toggle this setting going back and forth between TV and movie content.   Does the Preferred Refresh Rates option do anything here (I have not seen any impact)?  And does it work in conjunction with or independent of the Refresh Switching option?

Thanks,

 

[ebr 16182]

On 4/24/2023 at 7:01 PM, justinrh said:

It sounds like this 'enable switching' is another way of saying 'match video frame rate'.

Sorry, I missed this before.  Yes, that is exactly right.  In order to match the frame rate of the video, we switch your TV to the same (or a compatible) refresh rate.

[rbknox 6]

But the issue remains that you get matched frame rates at a cost:  your display will go black intermittently during viewing, presumably because a frame rate (falsely or otherwise) is detected.   So my question: is there another way to ensure that you have the right frame rate without enabling this?  That is, can you use the preferred frame rates in some way to ensure that movies for example play at 24 hz?   Or could there be an option where emby only checks frame rate at the beginning of playback and not intermittently throughout the playback?

[ebr 16182]

20 hours ago, rbknox said:

your display will go black intermittently during viewing

That sounds like bad media or the display misbehaving.

20 hours ago, rbknox said:

Or could there be an option where emby only checks frame rate at the beginning of playback

That's already how it is done. 

[rbknox 6]

On 11/26/2023 at 6:45 AM, ebr said:

That sounds like bad media or the display misbehaving.

That's already how it is done. 

Not sure what bad media would be.   Yes, I think the display is misbehaving, but why?

A specific example of what I am experiencing would be a CBS recording.  They broadcast at 1080i.  I recorded a football game over the weekend.   In this scenario, with the Display refresh rate switching enabled, things go okay during the actual game.  Stats show 30 hz video on a 60 hz display.  However, as soon as the broadcast goes to commercial, I get a black screen, followed by largely unsuccessful attempts to switch frame rates.  When I view stats, it seems the refresh rate is vacillating among several frame rates, changing to 24 hz, 25 hz and 30 hz.  While this is happening the display is alternating between a picture and black screen.   I have tried de-interlacing set to off, on and auto - similar behavior with double those rates when de-interlacing is enabled.  Set to gpu and other settings pretty much set to auto.

I validated this behavior on CBS with other shows.   This sometimes happens at the beginning of a broadcast - display is unstable even after the commercials so result is the show content also is unstable, at least initially.

If I turn Display refresh rate switching off, I have none of these issues and stats show 30 hz refresh on 60 hz display.   

[Luke 42078]

Is it really a good idea to turn this feature on for live tv? It's common for video to change during the broadcast (e.g. commercials). I'm not sure how well the switching will be able to deal with that.

My gut says that even if you enable the feature, the app shouldn't use it for live tv, interlaced video, and possibly other conditions.

[rbknox 6]

On 11/27/2023 at 1:04 PM, Luke said:

Is it really a good idea to turn this feature on for live tv? It's common for video to change during the broadcast (e.g. commercials). I'm not sure how well the switching will be able to deal with that.

My gut says that even if you enable the feature, the app shouldn't use it for live tv, interlaced video, and possibly other conditions.

Okay so I guess I'm a little confused.  If I leave it off, then when I play a movie, Emby seemingly ignores the fact that the movie is at 24 fps and plays it at 60.   If I turn it on, movies play properly but LIve TV has the aforementioned issues.  What is the best practice for setting up the app, given the varying types of media?  One shouldn't have to change the setting when moving between movies and live TV ...  Are you saying the app should be updated to ignore frame rate switching for live TV?   

[Luke 42078]

1 minute ago, rbknox said:

Okay so I guess I'm a little confused.  If I leave it off, then when I play a movie, Emby seemingly ignores the fact that the movie is at 24 fps and plays it at 60.   If I turn it on, movies play properly but LIve TV has the aforementioned issues.  What is the best practice for setting up the app, given the varying types of media?  One shouldn't have to change the setting when moving between movies and live TV ...  Are you saying the app should be updated to ignore frame rate switching for live TV?   

Right now it’s either on or off. We probably need to improve that and make it more conditional but we don’t currently have that.

[rbknox 6]

It seems to be that you have the answer - make refresh rate switching a feature of advanced settings for movie watching.  In fact, you could have movies play in their native frame rate by default, with an option to override or "frame rate switch" as an option.  Then just leave the TV shows alone ...