You’re running into a) Plex LG app limitations, and b) Celeron CPU limitations.
Hardware acceleration is working. However, Plex has to burn in the subtitles, which uses the CPU. The Celeron is not strong enough to burn the subtitles in real time, so the video buffers while the CPU can catch up.
See these posts:
Is the audio transcoding? Check playback via Plex Dashboard .
With the Plex webOS app, if the audio is transcoding, enabling any form of subtitles results in a video transcode.
Plex Media Server will burn the subtitles into the video stream. On Linux based systems, subtitle burning occurs on the CPU, even when using hardware accelerated transcoding. Furthermore, the process is single threaded. Systems with low power CPUs, such as the Celeron in your NAS, struggle with the subtitle burning p…
You’re running into the limitations of the Plex LG app (Samsung behaves similarly).
I have an LG B7 OLED. The limitations are one of the reasons I purchased a Nvidia Shield for myself and give Amazon FireSticks to my family/friends as birthday/Christmas gifts. The Plex Android TV app direct plays PGS, VOBSUB, and SRT subtitles even if the video or audio is transcoding (reference ). ASS subtitles still result in a video transcode and subtitle burn, but I’m not aware of any Plex client that h…
