It’s not a mystery, but there are a lot of differences in files around. Without being able to see and examine specific samples, it’s very, very hard (if not impossible) to say what an issue is to do with. We can only work with the information and samples that we have, and if people have problematic files, we can’t diagnose the issue without them. There have been quite a few different issues, to do with different file oddities, addressed over the last few releases, and this will continue, as we get more samples, and are able to look into issues.
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So I just discovered something interesting.
I moved one of my 2017 ATV 4K units to my office, which has an older 1080p (non-HDR) display. I played back some of my UHD rips to it via mpv, and noticed no stuttering. Clearly the ATV is negotiating with the display at 1080p SDR, but it’s still direct playing and decoding the full UHD/HEVC content.
Went to my bedroom, fixed the ATV to my LG display to 1080p60 HDR, and had the same experience. I’ve gone through my library, tested 10+ sources and zero stuttering while the ATV and TV negotiate output at 1080p60.
So far with about an hour of testing, I can confirm that my stuttering on any type of UHD content seems to only occur when the ATV is set for 2160p60 HDR (between both the 2017 and 2021 ATV 4k Models).
Some quick spot testings with the ATV set at the following resolutions/color spaces do not stutter:
- 2160p60 SDR
- 2160p50 HDR
- 2160p50 SDR
- 1080p60 HDR
I haven’t gone in depth on each resolution, but I can constantly replicate my issues on 2160p HDR and not on any of the other resolutions so far.
Update to some further testing on my last post as I was able to spend more time on this:
I’m still seeing issues with the content, but the issue/reproduction has changed. Using the list of resolutions above, content plays back smooth for 20-30 minutes, will pixelate/green screen, and then become a slideshow (with audio out of sync). Similar to the issue I described with SDR content in my first post on this thread.
The only exception is on the 2017 Gen 1 4k ATV’s (both of the units I tested for hours), I never get stutters when the resolution is set to 1080p60 SDR. There will be an occasional picture breakup/green screen (after ~30-45 minutes of playback), but no stutters after that. The 2021 Gen 2 stutters at 1080p60 SDR after this picture breakup/green screen hits. I assume this ‘green screen’ flash is something along the lines of a decoder crashing.
I had issues playing files for a long time, until I tried unplugging my Lan cable. Now Plex works like it should but my other services (obviously) prefer the the Lan connection.
I can’t produce sample files because with the Cable I can’t even reach my library, and the second I take out the cable it works. So yeah, before 8.12 this wasn’t an issue.
Curious how this issue could just appear.
hi @DaveBinM , now almost 2 months passed since I posted the stuttering sample file. Any update? Is it really that hard to fix this and revert back to normal performance in the past?
As we all know, playback via Infuse is perfect for these stuttering files, with the same Plex server.
I addressed that sample here. It’s a 60fps file, which our player is not performant enough to handle (and has never been able to handle), but we are working on improvements to this, but it does take time, and is complex.
Thanks for the update. I’m quite sure the title was playing fine a few months back. But I can’t be sure now as I couldn’t test old version of Plex app.
For now I can only use Infuse.
Will wait for your update.
Out of curiosity, does it play fine with ‘Old player’ (so internal Apple player) ?
I feel like old player is just superior to the new player in every way… except for some reason recently plex is just providing badly remuxed files to it.
Anyway, I agree Infuse is just better for playing content… except for lack of user accounts 
The codec and container support is very, very, limited in the old player, which was why we worked on implementing a different player.
I’ve been having issues direct playing any 4K HDR 24fps MKV content on my Apple TV 4K 2nd Gen (2021) for more than a month now.
Client Device: Apple TV 4K 2nd Gen 2021 (A2169)
Client version: 8.15 (5092)
Plex Server: Linux 1.31.1.6733
Client settings
Allow Direct Play: On
Use Old Video Player: Off
Auto Adjust Quality: Off
Home Streaming: Maximum
Internet Streaming: Maximum
Play Smaller Videos: On
@DaveBinM I just experienced this on the following file: (after 20 mins or so of playback. Stutters for 5 seconds then normal playback resumes. After a few minutes, stutters again)
Container: MKV
Bitrate: 13582kbps
Video Resolution: 4K
Frame Rate: 24fps
Video Profile: Main10
Codec: HEVC
Bit Depth: 10
Happy to privately send a test file- can’t post it here for copyright reasons.
Feel free to DM me a sample file
Will need to send an entire file because the issue seems to occur after 20mins or so of playback.
Do you guys not have any 4K 24fps Remux 10b MKV files?
@DaveBinM I DM’d you another file with really bad stuttering. Thanks!
Have you tried demuxing everything from the existing MKV using something like gMKVExtractGUI and then remuxing it back together manually into a brand-new MKV using something like MKVToolNixGUI?
I’ve also found that some MKV files occasionally need to have their bitstream timing corrected and framerate reset while remuxing:
I’ve always considered this an issue with the specific video files when I ran into this in the past and not an issue with Plex. I’d be really curious if these remuxing steps correct/fix the trouble files.
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I have tried this but it does not help.
I too have the problem that HEVC files over 11 mbit Bitrate dont play correctly.
I have one movie and one whole season of a series in which the picture is stuttering and seems that it is going by 0,5 speed but the sound runs perfectly fine. This is from second one and goes one the whole time (dont watched the complete episode but checkt for like 7-10 mins). I am watching via the Apple TV 3 4.
The same files working fine on other devices like MAC, Iphone, LG OLED, Chrome and via the old player and infuse.
@ DaveBinM do you still searching or working on the problem or is it solved from your persepitive?
Have you tried enabling the Legacy Player in settings? I know that they are trying to add additional features with the new player, but I’ve not had good luck with it, while the legacy player has been fine.
If you could provide a sample file, I can look and see if there is anything unusual about the file, or if it’s an issue we’re already aware of. The root cause of the issue in 8.12 has already been addressed, though we are looking at other playback issues with certain files.
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I have just checked something I was not aware of:
I have turned of “allow direct play” and the media is playing smoothly - In my test I had the feeling the sound is not sync but this might be the file …
But how direct stream is working while direct play don’t?
Using the mpv player…
Sure the mkv is beeing copied/extracted
Thanks for the idea - but really shouldn’t have to do this. Files playback just fine on PC, Android etc… But for some reason will not playback smoothly on Apple TV 4K.
Came across another one today.
Stutters immediately on Apple TV. Plays back perfectly on PC. (Server isn’t running on PC)
@Antigravity_83 - for the reasons you called out, I switched to Infuse as my player of choice for Apple TV. You can connect seamlessly with Plex Server without the playback hiccups.
