4k playback performance issue on certain files only

Plex Media Server NAS & Devices
1

Server Version#: 1.28.2.6151
Player Version#: Apple TV Latest

Hi,

I am fairly new to the forum so I am not 100% sure how to best help and provide description to my issues, happy to comply with any requirements.

Here it goes:

I have a fairly robust system:

  • local network is 1gbs and cabled with Cat 7 through and through - working great and very stable
  • player in the plex app on a 4k apple tv with plenty of space left and getting close to the maximum theoretical network speed limit on the 1gbs
  • plex server runs on on an Unraid dedicated machine: AMD Ryzen 5 5600G & 128GB of Rams and plenty of storage space, unless the server is transcoding 4k is basically never breaking a sweat

I have a lot of 4k content, mostly none Dolby Digital and mostly HDR (due to the colorspace issue on Apple TVs at the moment).
Most of my content plays beautifully, smooth, barely any buffering, etc.

But once in a while - and it tends to happen in series (like a given TV Show) - I’ll get some 4k (mostly HDR I believe) content that is basically unplayable… it does load fine, pretty never buffers, but the playback is extremely crappy ! No smooth, very jittery, etc. Special panning are horrible… it’s basically unwatchable.

My work around in those cases - are either to:

  • when the content is slightly jerky is to launch the content in Fuse - which always seems to be somewhat a bit smoother (but rarely perfect on that same content)
  • or sometimes to force the transcoding of the content (loosing HDR and resolution…) and most time the content will become buttery smooth
  • and sometimes for the reason the content won’t even transcode well at all, then I’ll go to the computer and pull up VLC and generally it’s perfectly played

The part that gets me is the inconsistance of it all… I can’t seem to pin-point any particular content (codec, format, bitrate, etc.) that does this. And sometimes in rare occasions it also happens with 1080p content…

The way this looks and feel makes me first think of performance issue… but I can’t seem to fine anything wrong.

In terms of Plex configuration it’s obviously possible that I have done something wrong… like for a while I was playing with RAM transcoding - which I since disabled because it consistently screws up the sync feature when I want to download content on my ipad, but I doubt it’s a transcoding issue considering I am direct playing the content 99% of the time…

Another point of note is that this seems to Apple TV specific as a content that will not direct play smoothly on Apple TV will play perfect on my desktop…

For instance this file, that we’ll call sample 1:

  • Codec HEVC
  • Bitrate 15074 kbps
  • Language English
  • Language Tag en
  • Bit Depth 10
  • Chroma Location left
  • Chroma Subsampling 4:2:0
  • Coded Height 2160
  • Coded Width 3840
  • Color Primaries bt2020
  • Color Range tv
  • Color Space bt2020nc
  • Color Trc smpte2084
  • Frame Rate 24 fps
  • Height 2160
  • Level 5.0
  • Profile main 10
  • Ref Frames 1
  • Width 3840
  • Display Title 4K HDR10 (HEVC Main 10)
  • Extended Display Title 4K HDR10 (HEVC Main 10)

Does not play well on AppleTV but plays well on Desktop

And this file (sample 2), plays perfectly on AppleTV (or anywhere for that matter):

  • Codec HEVC
  • Bitrate 31420 kbps
  • D O V I B L Compat I D 1
  • D O V I B L Present true
  • D O V I Level 6
  • D O V I Present true
  • D O V I Profile 8
  • D O V I R P U Present true
  • D O V I Version 1.0
  • Bit Depth 10
  • Chroma Location topleft
  • Chroma Subsampling 4:2:0
  • Coded Height 2160
  • Coded Width 3840
  • Color Primaries bt2020
  • Color Range tv
  • Color Space bt2020nc
  • Color Trc smpte2084
  • Frame Rate 23.976 fps
  • Height 2160
  • Level 5.1
  • Profile main 10
  • Ref Frames 1
  • Width 3840
  • Display Title 4K DoVi/HDR10 (HEVC Main 10)
  • Extended Display Title 4K DoVi/HDR10 (HEVC Main 10)

Or sample 3 works great too on AppleTV:

  • Codec HEVC
  • Bitrate 18671 kbps
  • Language English
  • Language Tag en
  • Bit Depth 10
  • Chroma Location left
  • Chroma Subsampling 4:2:0
  • Coded Height 1600
  • Coded Width 3840
  • Color Primaries bt2020
  • Color Range tv
  • Color Space bt2020nc
  • Color Trc smpte2084
  • Frame Rate 24 fps
  • Height 1600
  • Level 5.0
  • Profile main 10
  • Ref Frames 1
  • Width 3840
  • Display Title 4K HDR10 (HEVC Main 10)
  • Extended Display Title 4K HDR10 (HEVC Main 10)

Any clue as to how to figure out what is going on ? I am at a loss.

Thx !

2

Any suggestions ?

3

Sounds like you are noticing frame rate “judder” where the frame rate of the file differs from the output of the device.

Try enabling this setting:

Match Frame Rate:
Turn on to have Apple TV 4K or Apple TV HD match its refresh rate to the original frame rate of content. This applies to content that’s mastered at different frame rates — for example, 24fps film-based content or other international content.*
Turn on Match Dynamic Range or Match Frame Rate on your Apple TV - Apple Support

This judder situation can happen when playing DVDs on a 4K/BluRay player or basically any other streaming device.

Blurays are typically 24fps
DVDs are typically 30fps

So if a device is outputting 60fps to the TV, then DVDs would appear fine but since BluRays are 24, judder will be observed when frames are added to make up the difference.

4

Thank you very much for the answer.

I don’t believe that is it, because if I encode (via plex) the content, it will play fine - but most of the time I need to encode down to 1080p (because 4k will freeze every few seconds - complaining about power issue…).

So as far as I understand transcoding does not change the frame rate ?
But I’ll look further and see how the option is configured and test.

Thx !

5

Also I checked - the match frame rate and range was already enabled.

6

Anybody else has any ideas ? I am at my wit’s end on this…

7

Ok made an interesting finding.

The stuttering are gone if I enable: “Use old player” on the AppleTV Plex App.

I have yet to test enough content with this mode to see if that create other issues or not but it seems to solve my immediate issue.

8

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