MY Nas is QNAP 453Bmini，CPU is J345，I find J3455 is support for 4k X265 on intel.com， but in fact the performance of H265 on plex is very bad, only can play 1080 X265 smoothly
should i do somehing on the seting of plex?
Using Tautulli or status on app.plex.tv/web have you verified that HW is being used for both decode and encode?
Which version are you using?
The J3455 can easily direct play 4K x265 HDR movies. I’ve the Synology DS918+, which also has the J3455. I’ve no problem direct playing 4K material.
Transcoding 4K x265 is another matter (and best avoided).
The J3455 can transcode one 4K stream as long as h/w acceleration is enabled. It works, but I avoid it. First, Plex transcodes 4K to 1080p, so the video quality drops. Second, Plex does not tone-map HDR on most clients, so the colors wash out and the video looks very poor on screen.
If you are transcoding 4K, then make sure you have subtitles disabled. Enabling subtitles when transcoding video may cause Plex to use the CPU, not the embedded GPU, for transcoding. Transcoding a single 1080p video on the CPU is pushing it for the J3455. Transcoding 4K on the CPU is out of the question.
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If I may add to what FordGuy61 said,
Using PGS or VOBSUB (image based) subtitles, or any subtitles which require burning into the video stream, the CPU will be used. This is a substantial load on most NAS processors like the J3455.
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Thanks for the clarification.
I ran a quick test with PMS on my DS918+, playing a 4K HDR movie in Plex Web and monitoring with Tautulli.
No subtitles: Transcoded speed 1.4 - 1.6
PGS subtitles: Transcode speed 0.3
As expected given the limits of the J3455.
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@FordGuy61
@ ChuckPA
Thank you so much, It looks i have to play 4k x265 via HDMI
HDMI 2.0+ is your best option. I use it here and there are no difficulties.
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