Hello, I have a problem playing a 4k video, the movie “12 Monkeys”. The plex server is a Linux PC connected to my internet modem by a 2.5 Gbps wired connection. The plex client is a Samsung Galaxy S23 Ultra smartphone running Android 15. For a few minutes, the video is viewed without any problem, and suddenly the image starts to freeze for the first time, then more and more often. An examination of the transmission speed on the server shows that it has dropped, which explains the slowdowns.
One explanation that could be given is an instability of the wifi6 connection between the smartphone and the modem, but this is not in fact the case.
If you configure a samba file server on the server PC, and you view the film on the smartphone using VLC media player, the entire film, or 2 hours, is viewed without any slowdown. The server speed varies between 40 Mbps and 250 Mbps. The movie’s bandwidth is 100 Mbps.
How should I adjust my Plex client and server settings to view this iconic movie without lag?
Does this mean that 4k movies cannot be viewed in their original 4K resolution with Plex?
I should point out that I also just tried using an Nvidia Shield as a Plex client, connected by a 1Gbps line to the modem. Plex indicates that it is unable to read the media. To read the video it is necessary to activate transcoding. Conversely, if you use VLC on the shield and the Samba server, the movie is viewed without lag. The file container is MKV. The video codec is HEVC and the audio codec is DCA-MA (aka DTS-HD MA 5.1).
Note that the the Plex Server is a geekom A7 running linux : processor AMD Ryzen 9 7940HS with IGPU 780M. It is able to transcode the video, but this is not necessary with both the Galaxy S23 Ultra and the Nvidia Shield if you are not using Plex.
Here is the log file. Note that I cannot start communication if the wifi is cut off on the client side (the Plex server is not reachable). plex.log (639.7 KB)
4K is a larger stream bandwidth, so not only does your server have to be able to serve the data, your network also has to be able to support that data transmission.
On the network side, which is my specialty, my first Plex server had dual 1GB connections to my network. Keep in mind that port-channeling or LACP or teaming network that does not mean that the device combines the bandwidth, so not 2GB/s in that case. It means you have two 1GB/s connections so flow one goes through one network adapter and the next one uses the other and back and forth until one gets filled and then the other is used for subsequent flows. My new server is now on dual 10GB/s ports and its other four 2.5GB/s ports (connected at 1GB/s because my switch does not have 2.5GB ports) are used for other functions outside of Plex.
The next thing to keep in mind that the network card of the Smart TV or streaming device might not be 1GB/s. My TV at the time had a 100MB/s link. My highest bandwidth stream when I checked was Gemini at 4K with 145MB/s, so that 100MB/s link was the bottleneck.
People also use wireless a lot but their wireless network cannot support those higher bandwidth streams. With wireless, it negotiates best effort depending on how close you are to the access point (antenna), the amount of interference in the spectrum and how many devices you have connected. With the exception of the latest standard, you think of them as a room full of people trying to talk. It has to happen one at a time and everyone else has to wait. Now, those time slices are very fast but, 50, 60 or a lot of high bandwidth devices all trying to share can become a problem.
For this reason, I am a big fan of wired connections over wireless. Wireless is great for mobility. For places I have my streaming and TVs, I have wired connections to them.
Then, though if you have a 1GB switch or better, you look at the switch. Though, this is typically the least of the problems. You could get fancy with managed switches, which I did, and separate out VLANs to limit traffic seen between server and client. My IoT network is separate from my other networks. Wired is on a different VLAN than wireless. That helps eliminate how much broadcast traffic is seen on a VLAN since broadcast traffic does not hop across VLANs. So, if I have 100 IoT devices on my network, my streaming devices and server never sees that traffic.
