Network issues streaming 4K-Videos to an Apple TV over GBit-LAN

[info_mage_commerce_de]

Hi there,

I have a problem that appears to be caused by the Plex server.

When I try to play 4K videos (3840x1604 @ 31.1 Mpbs, HEVC, MKV) with DirectPlay on the Apple TV, it initially works without problems, but after about 5 minutes I get this message:

Your connection to the server is not fast enough to stream this video. Check your network or try low quality

Technically, this is nonsense, because the Apple TV measures 800 MBit via LAN to the server. So, it’s certainly not a problem of network speed. The problem sometimes also occurs with 1080P films.

If the film stops, it only continues with a stutter afterwards, so it runs for a maximum of 10 seconds without any interference. If I rewind, it takes about 1-2 minutes before the problem occurs again.

I tested different scenarios.

1. Plex Server + Plex-Client -> problem as described above

2. Plex Server + Infuse 6 Pro Client -> Instead of 5 minutes, the film runs for about 15 minutes, then there are the same problems

3. SMB server + Infuse 6 Pro Client -> The film runs smoothly

So, everything indicates that the Plex server is the problem. It stutters with different clients, although the network speed is more than high enough. If I play directly via SMB instead of Plex, everything works perfectly.

Do you have any idea what might be the problem?

Is it more of a bug or can you maybe change anything in the configuration of the server?

PS
About the technology I use:

Plex Server Version #: 1.18.3.2156
Plex Player Version #: 2.12.14020

The server is a virtual machine (Hyper-V) with 2 logical Xeon processors and Windows 2019 standard. The VM has a 10 Gbit connection to the main switch, the Apple TV has iOS 13.3 and is connected to the main switch via LAN with 1 GBit.

[deepseth]

I had similar issues with my ATV4 (1080p). It ships with a 100Mbps NIC instead of 1Gbps, but that should be plenty fast to stream a 20Mbps movie. Worked fine in other players, just struggled in Plex.

Looking at the BW monitor screen on the plex server, I could see that the client was just streaming at a very low rate. After I switched the ATV4 to wireless instead of wired, it would buffer at >100Mbps compared to streaming at ~8Mbps.

This may or may not work for you.

I’m assuming this is ultimately the mpv player failing at TCP window sizes, but haven’t bothered to pcap and validate this yet myself.