Poor 4K video playback performance in Plex

[Matt T]

I recently added a new 4K movie to my Plex library and noticed it’s video playback was incredibly choppy when I played it using the Plex app on my Apple TV 4K, to the point where some parts of the video were almost like watching a Live Photo instead of a movie - particularly scenes with wide shots featuring characters in the foreground and a moving landscape in the background. The video stats are as follows:

Codec: HEVC
HDR format: SMPTE ST 2086, HDR10 compatible
Bit rate: 21.0 Mb/s
Dimensions: 3840x1610 pixels
Frame rate: 23.976 (24000/1001) FPS (constant)
Bit depth: 10 bits

This isn’t even the largest or highest quality 4K file I have, but I’ve never noticed any playback issues with my Apple TV before. I went back and rewatched some of my other 4K files to check and they’re all playing back fine, so I assumed it was a problem with this video file. But then I decided to test playing it using the Plex app on my LG B6 TV and playback was perfectly smooth - so it’s not a problem with the file after all, it’s a problem with my Apple TV playing it.

I don’t expect there’s anything I can do to fix this, I just thought it was curious. Has anybody else noticed this too?

 

[waw74]

what's the audio, and what kind of audio playback device are you using?
is the server transcoding? everything? or just video or audio?
does it also do that when using the TV?
if it's transcoding video, how powerful is the machine you are running the server on.

the only issue I've had is playing back h.265 with surround audio, on a stereo tv. The video streams, but the audio converts, and it has real issues stitching them back together. if I set the video to convert it plays fine, or if I play on a TV with surround speakers, it also plays fine.

sometimes plex makes choices about streaming or transcoding that don't seem to make sense.

 

[RobbieTT]

In answer, no - I have no issues with high bitrate content from Plex.

Without knowing anything about your setup I don't think I can go much further than that.

 

[G5isAlive]

Have to admit the mysteries of Plex have alluded me... I know there are plenty who seem to have mastered it. I do recall hearing several people saying the Plex App on Apple TV really is not well optimized. Plex points fingers at Apple, Apple points at Plex. I do know that I never go it working to my satisfaction (stuttering) on the Apple TV.. but that an App called Infuse was able to read my Plex data base on my Synology NAS and worked fine for me. Thats when I gave up on Plex.

 

[Matt T]

Sorry for the late reply - to answer your questions:

what's the audio, and what kind of audio playback device are you using?
is the server transcoding? everything? or just video or audio?

The video file has 2 audio streams - 7.1 in FLAC which transcodes, and 5.1 in AAC which direct plays. The video is HEVC so it also direct plays. Neither audio option makes a difference to the video stuttering though. The audio plays directly through my TV speakers.

does it also do that when using the TV?

Nope - works perfectly using the Plex app installed on my TV, it's just the Apple TV app which appears to struggle.

But judging by this post on the Plex forums this seems to be a known issue: https://forums.plex.tv/t/example-of-stuttering-hevc-playback-on-apple-tv-4k/558255/62

It's suggested the issue is caused by video files which are missing a 'ctts atom', and remuxing the video files will fix them. I'm not familiar with remuxing so I haven't tried that yet - but it seems Infuse had a similar issue with these files and an update was released to fix it, so this should be fixable with a Plex update too. There doesn't seem to be any indication if or when an update will be released to fix it though.

 

[RobbieTT]

I tend to remux MKVs with Subler with the aim of achieving an HEVC in an MP4 container that is constrained to work with QT (on the basis that if it works in QT it will work with anything). It does mean that I lose Atmos / TrueHD audio though. Tend to peak at around 70Mbps or so and no issues with playback.

I've had a play of a few straight 4K HDR10, HEVC, all the audio and subs included in an MKV container with a file size of around 38GBs. Again, no stuttering on ATV Plex with a smooth playback. The start can be choppy though if an 'Analyse' has not been performed beforehand and the scrubbing experience is poor too, where as the Subler remux would have no such issues.

My media chain is:

SSD NAS (10GbE) > M1 Mac mini PMS (10GbE) > 10GbE Switch > 1GbE Switch > ATV4K > LG 4K OLED

If you are able to point at an example file that gives you problems I could test and compare if you like?

 

[steve62388]

Use Infuse. Over the years Plex has always had way more problems than Infuse.

 

[RobbieTT]

Use Infuse. Over the years Plex has always had way more problems than Infuse.

A somewhat unhelpful answer; the OP was asking about a Plex issue, not what player he should use.

Anyway, Plex and Infuse are not really comparable - for example, if you are using Plex for Live TV distribution and using DVR functions then a switch to Infuse would be a bone move.

Having some feature-overlap does not make it feature-comparable!

 

[steve62388]

A somewhat unhelpful answer; the OP was asking about a Plex issue, not what player he should use.

Anyway, Plex and Infuse are not really comparable - for example, if you are using Plex for Live TV distribution and using DVR functions then a switch to Infuse would be a bone move.

Is there some invisible ink on this page I haven’t seen? Because I didn’t notice anything about Live TV or DVR. I read that there was a problem playing a video from a Plex library on the Apple TV Plex app.

The Infuse Apple TV app can read a Plex library and almost always has fewer playback issues than Plex.

So to my mind, it’s a damn good answer.

 

[T'hain Esh Kelch]

A somewhat unhelpful answer; the OP was asking about a Plex issue, not what player he should use.

Anyway, Plex and Infuse are not really comparable - for example, if you are using Plex for Live TV distribution and using DVR functions then a switch to Infuse would be a bone move.

Having some feature-overlap does not make it feature-comparable!

Infuse can access the Plex library directly, and is a MUCH better client than the official one from Plex. Infuse plays practically everything, while the Plex client certainly does not, so the latter often relies on server transcoding.