4K DV/HDR HEVC Remux stutters/freezes with audio passthrough enabled

[privaty 4]

Hi,

since the recent update, playback of 4K UHD Remux files is no longer smooth on my NVIDIA Shield when audio passthrough is enabled. Before the update the same files played fine.

Setup:
- Emby Server: 4.9.5.0
- Client: Emby Android TV 2.1.23g
- Player: ExoPlayerLib/2.18.7
- Device: NVIDIA Shield Android TV
- Connection: wired LAN
- File type: 4K UHD BluRay Remux, MKV, HEVC, Dolby Vision/HDR, Atmos
- Example file name: Examble.German.Atmos.DL.2160p.UHD.BluRay.DV.HDR.HEVC.Remux.mkv

Issue:
With audio passthrough enabled, playback stutters/freezes or gets interrupted. The server log shows the client disconnecting during playback. If I disable audio passthrough, playback becomes stable, but this is not an acceptable workaround because I want to keep passthrough/Atmos and the same HDR/Dolby Vision playback behavior.

The Emby on-screen playback info on the TV reports Direct Play, but the server log / PlaybackReporting plugin shows DirectStream. The server serves /emby/videos/390/original.mkv and I do not see ffmpeg video transcoding for this playback session.

Observed in server log:
- Emby Server Version: 4.9.5.0
- Playback start reported by app AndroidTv 2.1.23g on SHIELD
- User-Agent: Emby/2.1.23g (Linux;Android 11) ExoPlayerLib/2.18.7
- Adding PlaybackInfo ... DirectStream
- Original MKV is requested via /emby/videos/390/original.mkv
- Repeated Range requests from the Shield
- Server reports: "Response completed after client disconnected"
- No ffmpeg video transcode load/error is visible

Expected behavior:
The file should play smoothly with audio passthrough enabled, as it did before the update. Direct Play should remain stable and should not freeze, stutter, disconnect, or unexpectedly fall back to transcoding.

Additional observation:
This is not limited to one movie. I have also observed similar behavior with other media files. Sometimes playback starts as Direct Play, but then Emby suddenly switches to transcoding during playback and the stream eventually stops. This did not happen before the recent update.

So there may be two related issues:
1. Audio passthrough causes stuttering/freezing with 4K DV/HDR HEVC Remux files.
2. Some files that should Direct Play suddenly fall back to transcoding and then stop.

Workaround:
Disabling audio passthrough makes playback stable, but this is not acceptable because I want to keep passthrough/Atmos. Also, when passthrough is disabled, the playback behavior appears to change and HDR/Dolby Vision output does not look the same on my setup.

Can you please check whether there was a regression in Android TV audio passthrough / ExoPlayer handling for TrueHD/Atmos with 4K Dolby Vision/HDR MKV remux files, and also whether the Direct Play to transcoding fallback behavior changed in the recent update?

I can provide server logs for both cases:
- Direct Play / passthrough stutter with client disconnects
- Direct Play unexpectedly switching to transcoding and stopping

embyserver.txt

[ebr 16465]

Can you please play that item until it exhibits the issue and then follow the instructions to send a log from the app?