A long thread with good information on Plex & 4K: [INFO] Plex, 4k, transcoding, and you - aka the rules of 4k
If you plan to run Plex Media Server on the DS920+:
- Do not install DSM 7 beta. Plex support for DSM 7 is currently very limited. Current Plex Media Server builds are DSM 6 specific. They will not work on DSM 7 without workarounds. There is a DSM 7 pre-production build, but it has issues, some caused by DSM 7 bugs.
- Do not install the version of Plex Media Server in the Synology Package Center. It is outdated. Download the current Synology Intel 64-bit version from plex.tv/download and perform a manual install. How to do so is explained in the following two documents.
- Read Installation & Setup of Plex Media Server on Synology
- Read Synology FAQ - Questions, Answers, and a few How-To’s
No. You do not want to transcode 4K media. You want to direct play or direct stream media.
The CPU in either the MacBook or NAS is not strong enough to transcode 4K in real time, so you will experience buffering. Reference: What kind of CPU do I need for my Server?
Transcoding destroys any HDR information in the file. Plex transcodes all video to H.264, which does not support HDR.
You do not have a Plex Pass, so you cannot take advantage of hardware accelerated transcoding (using the graphics processor of the Intel CPU in your MacBook or NAS).
Plex Dashboard → Now Playing will show you if the media is direct playing, direct streaming, or transcoding. You want direct playing or direct streaming.
MKV or MP4. AVI is an older format.
Unfortunately, there is no one location to find out the capabilities and limitations for all Plex clients. You have to read the device specifications and ask on the forums.
From the datasheet for your Samsung, notice that it does not support TrueHD or dts audio formats. Selecting either audio format in the Plex client results in Plex transcoding the audio.
The supported audio formats are important given the limitations of the Samsung Plex client:
- Enabling image based subtitles, PGS or VOBSUB, forces a video transcode by the Plex server.
- Enabling ASS subtitles with font/position/etc information forces a video transcode by the Plex server.
- If the audio is transcoding, enabling subtitles of any type forces a video transcode by the Plex server.
- If the audio is not transcoding, then SRT (text) subtitles will direct play (not force a video transcode).
What it boils down to is when you are using the Samsung Plex app, especially when watching 4K or any HDR material:
- Do not enable PGS/VOBSUB/ASS subtitles.
- If you use SRT subtitles, do not use TrueHD or dts audio (including dts-HD/dts:X).
There are other limitations of the Samsung Plex app of which you should be aware:
- Media with HEVC/H.265 video is limited to 80 Mbps.
- Media with AVC/H.264 video is limited to 60 Mbps.
- All media can have no more than
3530 tracks (video + audio + subtitle).
Exceeding any of the above can result in video or audio transcodes.
The TV’s Ethernet port is most likely a 100 Mbps port. No known TVs have 1 Gbps Ethernet ports. This will be important if you are streaming high bit rate 4K media, which may burst above 100 Mbps. If this happens, you may notice buffering even when the media is direct playing.
If you’ve a strong 802.11ac 5 GHZ signal at the TV, you may have better results connecting the TV via WiFi instead of wired Ethernet.
Some additional information:
Plex Documentation
→ SmartTVs & Tivo → What Media Formats are Supported
→ Direct Play, Direct Stream, Transcoding
