Server Version#: DSM 6.2.4-25556 Update 7
Player Version#: 1.32.5.7349
Hi All,
Been having issues specifically with buffering on local network only. I’ve been able to confirm with some friends who have access to my plex from outside my network that they haven’t had any buffering issues.
When trying to play video either on desktop, tv app, or the xbox app, I get constant buffering issues. Shows and movies will buffer and I’ll get maybe 1 minute of content before it needs to buffer again for another 5-10 min.
I don’t believe that this is network related as, if I access the files directly on my computer there is no buffering issue, it’s only through the Plex app specifically.
I have tried adjusting the video quality of the streams along with ensuring that the quality being sent is below what the upload speed that my network is capable of.
Sep 11, 2023 18:44:14.312 [139889466993464] DEBUG - [Req#7ad/Transcode] MDE: E14 - Stanley's Cup: selected subtitle cannot be converted to a compatible format, burning into video stream
The log file shows you playing an episode of South Park that has ASS subtitles using the Firefox browser.
The subtitles are incompatible with Plex Web/Firefox.
Therefore, Plex must transcode the video and burn the subtitles into the video stream.
Subtitle burning uses the CPU, even when transcoding using hardware acceleration.
The Celeron J3455 CPU in the DS918+ cannot burn the subtitles in real time, therefore you experience buffering.
Alternatives
Do not use subtitles.
Use subtitles in a compatible format.
SRT is generally compatible with most Plex clients.
You can use tools such as Subtitle Edit to perform the conversion.
You can monitor playback via Plex Dashboard → Now Playing + Expanded View. This will show if the video or audio streams are transcoding. Since subtitle burning uses the CPU, you will see the CPU utilization spike when that happens.
You can also monitor playback using Tautulli, which shows if subtitles are being transcoded or burned into the video stream.
Adjusting the video quality will make little or no difference. It forces a video transcode and subtitle burning, which is already happening.
For local playback, the Internet upload speed does not matter, as all traffic is local.
