Plex insists on transcoding HEVC>H.264

Plex Players Streaming Devices
12

Similar issue here on my Android TV 9.0 box with latest Plex app:

My box itself can decode x264 and x265/HEVC video streams up to 4K as well as DTS and (E)AC3 audio streams. When I play a 4K HEVC+EAC3 video with audio output just on my box (optical or HDMI passthrough both disabled), everything works smoothly without any transcoding.

Now I have a 5.1 audio system which I have connected to my box via SPDIF that can handle DTS and vanilla AC3. As soon as I enable the optical passthrough in the plex app (with DTS and AC3 options enabled in the Plex app’s settings), playback of a non-supported audio codec such as EAC3 turns on audio transcoding to AC3 as expected. However, for no apparent reasons this also forces the video (e.g. HEVC which worked fine before) to be transcoded to h264 (WTF?!), although my box is perfectly able to decode the original video stream directly… What is going wrong here?

I already tried raising/disabling the h264 level in the plex app, and switching to the “old player”, however to no avail. (No surprise because h264 limitations on the client shouldn’t affect HEVC streams, should they? The explicit reference to “h264” and absence of a similar “HEVC level” setting in the Plex Android app makes me wonder about its awareness of HEVC profiles/levels…)

Could you fix the logic behind this, so only those streams are transcoded that need transcoding (i.e. here: any streams not supported by the chosen audio output) and the other streams that can be played directly are played directly (i.e. here: the video streams that are completely unaffected by the audio settings and fully supported to be played directly by the TV)?

Thanks a lot!

PS:

  1. This problem looks quite similar/related to
  2. Note: Subtitles are disabled.
  3. I get the following related console messages:
    [Transcode] MDE: no remuxable profile found, so video stream will be transcoded
[Transcode] MDE: Cannot direct stream video stream due to profile or setting limitations
    Not sure what this means though, the affected videos are stored as .mkv containers.
  4. Things seems to work properly with the Plex app on my Android 9.1 smartphone, where it does transcode only the audio but leaves the video stream alone as “Copy (HEVC)”.
  5. Plex Server version is 1.21.2.3997.
  6. Plex Android app version is v8.11.0.22186(a1b8a7fb) both on my smartphone (where things work) and the TV (where things go wrong), although their look and feel is quite different.