Remux Dolby Vision Audio becoming PCM

[azianxbaka]

Hey guys,
Hoping there is an easy fix for this. 

Some info on my setup:
Using Jellyfin WebOS app on LGC2
Receiver is a X3800H.
Hosting Jellyfin 10.9.11 on truenas scale with a GTX 1660 super.

My problem is whenever playing a Dolby Vision MKV remuxing, the Audio signal sent to the receiver becomes PCM instead of Dolby digital.
This only occurs in the Dolby vision videos. If I play videos with only HDR, it will direct play and the audio signal sent to the receiver will be correct.

Any help with this would be greatly appreciated.

Thank you.

[TheDreadPirate]

Probably because the video is being transcoded. Is that the case? Can you share your log via pastebin?

[azianxbaka]

Thanks for taking a look at this.

https://pastebin.com/Eay66KHL is the ffmpeg log for the remuxed DV video file.

[gnattu]

It really looks like LG TVs need some special treatment because its native HLS player has a lot of quirks. If you want both Dolby Vision and Dolby Digital passthrough on your current TV you might need to remux the file to mp4 container by yourself and don't use mkv for now.

[azianxbaka]

Darn, seems like just gotta wait for future updates then.

If this is the case, would you guys happen to know how to force HDR fallback or turn off Dolby Vision in jellyfin configs?

[TheDreadPirate]

You could use the quality selector and select a bit rate that is lower than the video's native bit rate. This will force a transcode + tone map.

[gnattu]

You could use the quality selector and select a bit rate that is lower than the video's native bit rate.  This will force a transcode + tone map.

This won't help OP's problem as transcoded video is still delivered with HLS and the problem looks like LG TV's HLS player cannot passthrough Dolby Digital directly to his audio system and will always decode to PCM. The ultimate solution is to add a new option in LG client so that the user can force direct play mkv files (at the cost of no dolby vision and only HDR10 fallback), and even better, add an "optimize" option in the server so that the server remux this file to mp4 beforehand so that the TV can play it directly and be happy with both Dolby Vision and Dolby Digital Sound.

[jasmus]

I've just been setting up Jellyfin on my LG C4 and have come across this post. I think I'm seeing the same thing. The C4 reports "Dolby Vision + Dolby Atmos via soundbar" at the top right, but it's actually only reporting 'Linear PCM' on my Samsung soundbar. Remuxing the source file from mkv to mp4 (Shutter Encoder, MacOS) results in a file that plays Dolby Vision on the LG, and correctly outputs Dolby Atmos to my soundbar.

So, what's going on here and why is the Jellyfin remux different to a manual remux? Is it something we can create an issue for on github? What's different about a local mp4 supporting DV + Atmos vs a Jellyfin remux of the same content from mkv?

It was my (albeit, perhaps novice) understanding that the Jellyfin feature would remux from the mkv container to mp4 on the fly, but that may not be the case.

Edit: Ah, looking at Jellyfin logs, it seems it might be remuxed to HLS-TS, which could be part of the issue. My client currently has "Prefer fMP4-HLS Media Container" unchecked (default). Perhaps setting this would force an mp4 remux...will have to try that and compare results.

[TheDreadPirate]

Edit: Ah, looking at Jellyfin logs, it seems it might be remuxed to HLS-TS, which could be part of the issue. My client currently has "Prefer fMP4-HLS Media Container" unchecked (default). Perhaps setting this would force an mp4 remux...will have to try that and compare results.

IIRC, prefer fMP4 is currently bugged in WebOS.  I can't recall if this is a WebOS problem or a Jellyfin problem.  It USED to be on by default but has since been off by default on WebOS and should stay off for now.

[jasmus]

IIRC, prefer fMP4 is currently bugged in WebOS.  I can't recall if this is a WebOS problem or a Jellyfin problem.  It USED to be on by default but has since been off by default on WebOS and should stay off for now.

Thanks for the reply. It certainly seems bugged to me. Switching it on results in a splash screen and an endless loading spinner. It never gets to playing the media and I need to force exit the Jellyfin app to do anything else. Logs show it's remuxing using mp4 but that's it. It doesn't work.

That's a bit of a shame. I was hoping to avoid remuxxing these DV+Atmos source files to mp4, since it seems a bit of a pain in the butt when it comes to subs (and I think chapter markers too), but I'd rather have the full audio experience so I guess I'll need to. That, or hope that somehow the problem with media player's handling of the HLS-TS remux audio is fixed (unlikely I'd say).