I forgot HDR Tonemapping was a Plex Pass only feature. Ideally you will not need it, but sometimes it is necessary.
You want to direct play media whenever possible, especially 4K HDR. When direct playing, Plex Media Server sends the media to the client (i.e. Plex app) unaltered.
Plex sometimes has to repackage the video/audio/subtitle streams. This is generally referred to as remuxing. Plex also calls it Direct Streaming. This can happen for several reasons. One common reason is when the media contains an audio track not supported by the client. Plex transcodes the audio to a supported format, then repackages it with the video & subtitles and sends it to the Plex client.
If Plex cannot direct play or direct stream the video, it will transcode it. Most of the time this is not too much of a problem. However, 4K HDR is a special case. The output of the Plex video transcoder is always SDR video. Also, to make the colors look correct, the Plex server must tonemap the HDR to SDR colors. Otherwise, the colors look “off” or “washed out.”
This is where you start to run into the limitations of the Plex Smart TV apps. It is easy to inadvertently trigger a video transcode and suddenly you are watching SDR video. It still looks good (as long as it is tonemapped), but it isn’t as good as HDR video.
With the Plex Samsung app, if Plex is Direct Playing, enabling subtitles is not a problem.
However, if Plex is Direct Streaming, enabling subtitles results in a video transcode, which means you’re watching SDR, not HDR, video.
As mentioned earlier, Samsung does not support TrueHD or DTS audio formats. When you play a file with those formats, they will be transcoded by Plex Media Server to a supported format. Plex will recombine the video and audio and direct stream it to the Plex app. This is all OK. You will get HDR video and transcoded audio.
The problem arises when you enable subtitles. Direct Streaming + subtitles results in a video transcode. Then you are watching tonemapped SDR video instead of HDR video.
That is why I mentioned avoiding subtitles when playing a TrueHD or DTS audio track.
Blu-ray movies with TrueHD audio also have a Dolby Digital audio track. If available, play the Dolby Digital audio track instead, as it will direct play.
Unfortunately, movies with DTS audio generally do not include a Dolby Digital audio track. Therefore when playing DTS audio, do not enable subtitles or the video will transcode.
To condense all of the above into four lines:
- Dolby Digital + Subtitles = OK
- Dolby Digital Plus + Subtitles = OK
- TrueHD + Subtitles = video transcode
- DTS + Subtitles = video transcode
I hope I’ve explained things clearly and not confused you. Unfortunately, the issue with subtitles is not in the Plex documentation. Most people run into it and don’t understand what is happening.
As far as the Plex Pass goes, it is good you have it so you can tonemap when needed. I’ll correct my earlier post.
