Server Version#: 1.25.2.5319
Player Version#: 8.27.2.29938 (4e119b4b) (Android 9)
DONE
Plex Media Server Logs_2021-12-27_22-49-15.zip (510.0 KB)
When playing a mkv file, H265 4k resolution, HDR, with EAC3 audio stream on booth my android 9 device which supports H265 hardware decoding and my nvidia shield, which also supports H265 hardware decode, Plex media server running on linux debian should just transcode the EAC3 audio to AAC/OPUS/etc, but not transcode the video since the device can play the 4k H265 video without problems.
Turns out, when the audio transcoding is triggered, the video transcode also is triggered without the need, because the device resolution is lower than the 4K source file resolution. (as showed in the logs)
Directplay is enable on booth android devices and plex media server.
If I convert the media file EAC3 audio stream to AAC (using ffmpeg I just trancode the audio stream to AAC 5.1 channels, and copy the H264 4K HDR video stream over to a new mkv file), booth devices (android 9 phone and Nvidia Shield) play the 4k/aac media file through DirectPlay, without transcoding! (which proves the hardware is totally able to play the the 4K H265 HDR video stream without issues)
If you look at the attached Plex Transcoder log, at “Dec 27, 2021 22:28:02.926”, you’ll find one of the unnecessary transcodings of a 4k/EAC3 video stream.
- I’ve noticed this behaviour happening with 4K AC3/EAC3 videos.
- Playing 4K AAC videos play with directplay without transcoding on 1080p devices.
- I’ve also notice the same behaviour with 1080P EAC3 files, where the 1080P video stream will start transcoding as well. (in this case, there’s not even a resolution difference!)
- Playing 1080P AC3/AAC files play with directplay without transcoding. (I was surprise to see AC3 files playing without transcoding audio, but EAC3 files will trigger the audio transcode, and consequently trigger the unnecessary video transcoding!)
All this examples (4k AC3/EAC3 and 1080p AC3/EAC3) are in the logs!
In my understanding, when audio transcoding is necessary, it shouldn’t trigger a video transcoding as well when the playing device can support playing the original video stream, even if the original resolution is bigger than the playing resolution. The players can downscale pretty well, and it’s actually desirable to downscale from 4k to 1080p in most cases.
I actually prefer to play 4K videos on my 1080p projector since the 4K video gives me a better, more crispy image after being downscaled by the device, than playing a media file already at 1080p. Not to mention the downscaled takes care of the compression artifacts completely.
I also prefer to keep my source video files in AC3/EAC3/DST/ETC, so I have the option to use a multi-channel audio system with audio passthrough in the future.
I also run my plexmediaserver without a video gpu, so my hardware can’t encode 4k video at all… Because of that, I’m not able to play any 4K/AC3/EAC3 content with plex on any device I have.
My only option at this point is to convert the files manually to a ACC audio stream.
