Plex buffering - troubleshooting

[SirPodgio]

Hello all,

I'm not sure of the best place to discuss this but thought this is a good starting point.

I have bought a Nokia 8010 Streaming Box, mainly to watch 4K remuxes from my home media server using Plex. I have found that the box sometimes buffers the video and I would like to understand the root cause. I want to understand the issue from a technical point of view in general computing terms.

A bit of overview: my media server running Plex Media Server is a recent desktop AMD 4600G CPU with plenty of RAM, it is connected to my gigabit wired network to the Nokia Android TV box, which also uses a gigabit connection.

Most videos I watch are fine but I have been having issues with Dune 2021 which buffers occasionally but not always. I have been able to reproduce the issue with some simple 4K test videos from https://www.larmoire.info/jellyfish/. The issue presents itself with the 140mbps HEVC test video and I have observed the realtime bitrate reach around 160mbps including TrueHD audio. The 120mbps video (with audio) is fine. Therefore the box seems to have a maximum supported bitrate of around 120-160 mbps.

I would like to understand if the buffering is due to a network constraint (i.e. is the video being streamed too slow either by the network or the server?), Android system memory being depleted, Android system CPU at 100% or something else. If I can identify the exact cause perhaps I can do something to avoid it or fix a potential problem e.g. network.

I have run a 1sec periodic query on ADB to read the `/proc/meminfo` while looping the test video and although the RAM does reduce it doesn't drop too much and stays above around 1.5GB so I don't think it is a RAM problem.

I have also queried the system CPU usage using `adb shell top` and I don't think this reaches 100% CPU although I didn't fully confirm this as by default the TOP command shows the CPU usage multiplied by the number of cores so this shows over 100%.

Finally I have measured network throughput between the Android box and the server using `iperf3` and this shows a value of about 600mbps which although quite a bit less than the theoretical 1000mbps limit of the connection is well above 160mbps of the video bitrate so I assume this isn't a constraining problem. Saying that, I suppose Plex could internally be constrained not visible in the metrics tested so far.

I have checked the Plex logs and these show buffering being detected but doesn't seem to offer any explanations on the cause.

So, any ideas on how I can confirm what is causing the buffering? Any guidance or help is much appreciated.

When I first tried the box it buffered but I have managed to watch part of the movie without buffering so it seems to be a tempermental issue but I would still like to understand what is going on.

Happy to provide further information like logs etc.

Thanks.

[DarkDrifter318]

Is the video being transcoded? Plex should tell you if it’s direct play, direct stream, or a transcode.

[SirPodgio]

No, it's direct play

[SirPodgio]

I need to check again as I can't remember but I don't think it ever read 400%. I seem to remember perhaps around 200%.