LG C9 Plex App Sudden buffering

Plex Players Smart TVs
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Server Version#: 1.25.2.5319
Player Version#: LG Plex Player app, version unknown
(The “about” page says “client 5.29.1” and Platform 4.9.0" / App page says version 5.01)

All that said, I’m using my WiFi Mesh (Linksys Velop AC4400) network to stream from my iMac Plex Server. For the most part it has worked well. However, last night we tried to watch a 1080p movie and it buffered too badly to watch (note that the native file shows a 26,000 bit rate, extremely high for an old black and white 1080p movie). Note I have the same model TV in my “Man Cave” with a faster WiFi connection and it played almost perfectly (2x short bufferings).

This morning I realized that one of my Linksys mesh routers was offline (using my iPhone Speedtest I found it running at a measly 5 mb/s )…actually it was the one by my Man Cave TV so go figure. I reset the router thinking I’d found the issue (now my iPhone is running at 200mb/s).

Nope, movie still buffered madly. I went into the movie settings and confirmed the 26Mb/s value and pushed it down to 8mb/s (lowest setting that used 1080p). Better, but still buffering although not as frequently nor as long.

Bottom line, this never used to happen. The network transfer rate is plenty high (the numbers above are Internet D/L rates, I would think my internal network would be much faster).

I have one more Mesh unit I can install, and I’m looking at ways to run a hard line from my computer to the upstairs TV, but I think that I shouldn’t have to do either. The network is plenty fast.

Note: My movies are on a DS920+ NAS which should have plenty of read speed.

Any other ideas?

Thanks!

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Reproduce the problem and upload logs.

Are subtitles enabled?

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Set the Plex app on the TV to log to the server at the debug level first, then re-create the problem and pull the server log files.

The Plex LG app has poor subtitle support. This can cause buffering on systems with low power processors such as the Celeron CPUs in Synology NAS.

Enabling PGS or VOBSUB subtitles forces a video transcode.
If the media is direct streaming, such as when audio is transcoding, enabling any subtitle results in a video transcode.
If Burn Subtitles = Automatic, enabling ASS subtitles results in a video transcode.

When that happens, Plex must burn the subtitles into the video stream. The burning process occurs on the CPU, even if hardware acceleration is enabled. It is also single-threaded, so cannot take advantage of the multiple cores. The Celeron processor will struggle to burn subtitles in real time, especially on higher bit rate video such as Blu-ray rips. When this happens, you will experience buffering.

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No subtitles. And the Plex server is on my high power iMac, not on the NAS. NAS is just for storage.

As for the logs, I turned them on then played the problematic movie. Dammed if it played perfectly. In aircraft maintenance this is called “CND” (can not duplicate). #sigh

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