Firestick, EAC3 5.1 Audio only playing as PCM Stereo

[ke8ort]

Hello all! Normally I don't like making posts about questions as basic as this, however it seems that Jellyfin has changed a whole lot during the past few years and pretty much every previous post on this matter doesn't apply to modern Jellyfin.

Some backstory: I am trying to make a good case to switch from Plex to Jellyfin, so I am running both in parallel right now and trying to do some fair comparisons. On my mobile devices, swiftfin has been serving me perfectly, providing good streaming quality and no issues. On my firestick, however, it is not going so smoothly.

Information about my setup: Currently, how I have things setup on my TV is as follows: I have an older Vizio TV (hand me down from my parents, pretty good for a "free" TV), and an even older receiver. I have the receiver connected to the TV with an optical cable and the firestick is connected to the TV via HDMI. On Plex, I was able to get 5.1 and DTS support working by just telling plex to passthrough the audio as HDMI instead of optical. With this, I was able to watch my movies with full surround sound. Jellyfin is only giving me PCM Stereo audio whenever I play the exact same file, and no amount of messing with settings in plex or in the firestick settings is working. Both the Jellyfin server and the client are the latest versions, and Jellyfin is running in a docker container. 

What I have tried so far:
- Jellyfin Direct Play Audio and Bitstream Dolby Digital are enabled
- Firestick settings: auto for Dolby Settings

Looking in the admin dashboard for Jellyfin, it claims that my file is direct playing on the client. I have verified that it still works on Plex, and that when I play the file on my PC with VLC, the audio codec is 5.1 EAC3. 

I have tried to follow many previous posts that have similar trouble, and most of them involve downmixing all audio to stereo (not what I want to do, I'm trying to give this a fair run against Plex), or changing the built in player, which as far as I can tell, is no longer a setting in Jellyfin for FireTV. I don't know if anyone has any experience with this. Any help is appreciated!

[theguymadmax]

I don't think there's a setting for this. You only have options for Direct and Stereo. As far as I can tell, EAC3 isn't fully supported over optical audio. When you use Plex, is it transcoding EAC3 to AC3?

Also, worth a try. Do you have refresh rate switching turned on? If you do, try turning it off.

[ke8ort]

It's possible Plex is transcoding EAC3 into AC3. I did try a few more files and it seems that if it is an AC3 audio track, it will play it properly, however AAC 5.1, EAC3 5.1, and DTS codecs will play as stereo. Unfortunately, I have very few AC3 files. Beginner question: Can I set Jellyfin to transcode EAC3 into AC3?

I have looked in the Jellyfin settings but can't find it, where should it be located?

[theguymadmax]

Unfortunately, there is no setting for this. The closest setting would be this open PR.

[ke8ort]

That PR seems to be implementing the same sort of feature as I enabled in Plex to get 5.1 to work on more than just AC3. I'll keep an eye on it in the next few weeks. Thank you for your help!