LG plex app - Video HW Trascoding + subtitle -> high cpu low gpu usage

Plex Media Server
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PMS version: 1.31.2.6810
Windows: win10 64

gpu: nvidia geforce gtx 1060 3gb
gpu driver version: 531.29

LG webOs version: 04.40.70
LG plex app client version: 5.56.1
LG plex app platform version: 5.4.2

Hi, it is a bug or i can’t configure correctly something, maybe LG webOs “feature” ?

If i transcode a video and set subtitle, the transcoder use much more cpu instead of gpu, and for this reason buffering every 5-10seconds

hw+sub
hw+sub989×506 43.1 KB

But, if i don’t set subtitle, the transcoder use gpu with a minimal cpu and can stream continuously

hw
hw1051×476 43.2 KB

Why use the transcoder the cpu instead of the gpu if i set subtitle to the movie?

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Plex is burning the subtitles into the video stream. This uses the CPU, even when hardware accelerated transcoding is enabled. Plex does this to keep the video, audio, and subtitles in sync with each other. It is due to a limitation in the streaming protocol used between the Plex client & server.

Other than not using subtitles, there is nothing you can do to avoid it.

On a separate note: Make sure you are running the 64-bit version of Plex Media Server. It is more efficient at transcoding & tonemapping HDR to SDR than the 32-bit version.

To determine which version you are running, look where the binaries are installed. If they’re in c:\program files (x86), then you’re running the 32-bit version.

You can download the 64-bit version from plex.tv and install it on top of the 32-bit version. The installer will uninstall the 32-bit version first.

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