I have the same issue as @brettuk using an RPi4 emby server (docker container) streaming to Apple TV 4k emby app.
Playing an mpegts container with mpeg2 video and aac audio works fine as a Live TV channel or as a completed recording (i.e. no transcoding).
Playing an in progress recording causes emby to transcode the video using libx264 and copy thru the aac audio.
This happens for both DVBT and DVBT2 streams i.e. mpeg2 and h264.
I have some raw video streams that tvheadend transcodes into mpeg2/aac/ts on the same Rpi4. The RPi4 can do this quite comfortably and feed it to emby for recording/playback, but when emby also transcodes it again it hasn't got quite enough grunt for two simultaneous transcodes so the video stutters a little.
Edited by sihy, 24 November 2019 - 09:25 AM.