Why jellyfin don’t build direct play mkv

[GOBOXS]

Why jellyfin always transcode and direct stream (restream look like transcode) mkv to mp4 , devices compatible but jellyfin still wxport mkv to mp4 , why ?

[Efficient_Good_5784]

This entirely a client issue.

If you want to direct play MKV containers, you need to be using Jellyfin Media Player or MPV Shim as both of these clients use MPV which does support MKV.

If you're talking about a browser like Chrome, it can only direct play some video codecs (like HEVC) as long as it's packaged in a MP4 stream container.
We have no control over that. If you want Chrome for example to support MKVs for all things, you need to talk to Google.
Or the same for whatever client you're using. They need to implement support for MKVs.

All the Jellyfin server does is send a stream or a transcoded/remuxed stream if the original isn't supported.

[TheDreadPirate]

To add to what efficient stated, browsers can support MKVs. But only if you play the FIRST audio and subtitle track (if you have subtitles enabled). If you select any other audio or subtitle track, at a minimum it will need to be remuxed and the remux will either be MP4 or TS.

[GOBOXS]

yes i know that , web or some devies don't compatable with mkv and dts , but i want talk with devies compatable with mkv , but jellyfin direct stream (what direct stream ? it look like transcode make from mkv to mp4 and send back client ) , i know jellyfin use ffmpeg , but why don't make same emby or plex , direct play , same device and same file emby and plex direct play no need change to mp4 , jellyfin is make mkv to mp4 (direct stream) , trandcode or directly stream it same still use hardware for do it , so if still do this way , can not play more device onetime ,

i tried make 1 flask script try jellifin know video file is mp4 (original is mkv) = jellyfin direct play , but seeking jellyfin again direct stream , seeking again jelly direct play , i make sure jellyfin can not play 10 devices onetime , because cpu always 99% (direct stream) , don't ask me my hardware , because i used more server for over 14 years , and i build more plugin and addon , when i tried jellyfin some month , i really disappointed , really jellyfin just play hls is perfectly , and mp4 .

[Efficient_Good_5784]

Transcoding audio and/or repackaging the stream to a new container is not that resource intensive.
We would need to see your ffmpeg logs to see what is happening.