PLEX - AAC 5.1 vs AC3 5.1

by architect5150

Setup : Plex media server with transcode capability (try to direct play as much as possible) Sony X850C Android TV with Play Store loaded Plex App. ARC channel to Marantz SR5009

AC3 works fine, besides the fact I get a slight, almost unnoticeable video "slow-down" every 2 seconds or so only on videos converted from itunes m4v to mp4. I have Mad Max Fury Road in 4K in an M4V container that is flawless in both video and audio playback. At least this way I can get dolby digital pass through to work to my receiver and upmix from 5.1 to 7.1 from there.

Why, then, do I not get pass through "multi-channel in" from a video that has 5.1 AAC? I get direct play, but am only getting stereo to my receiver, which means Android TV or my TV is downmixing it to stereo signal rather than passing it through, correct?

How do I get Plex (and Kodi if possible) to be able to pass all AAC 5.1 channels through to my receiver over ARC? Is it because it is not compressed enough and doesn't have the bandwidth needed?

I'd rather not go back to my 150+ movies that use AAC and convert to AC3, but I'd rather do that than upmix a stereo signal.

Let me know, thanks!

rhkratos

Random aside...AAC5.1 only works when you are running your audio over HDMI (If you are using an optical you can only do stereo if you aren't running AC3/DTS).

As others have said, passthrough over ARC really doesn't work well (and is very TV dependent). If you bought a dedicated device for Kodi/Plex (say a nvidia shield) then ran HDMI from shield to receiver, and HDMI from receiver to TV you will have no issues with any of this provided your receiver supports whatever audio format you are running.

Andrroid

Can you enable the on screen display in the Plex app and let us know what it says in the top left of the screen when you play this content back?

Ogi010

Hey,

So I'm not sure if this issue is relevant to you, but right now on the Nvidia Shield anyway, there is an issue with audio passthrough. On my shield, the video crashes a few seconds into it, or if it doesn't crash there are discolored frames periodically.

I read up on the Plex forums, and some people reported that they got good results by disabling automatic frame rate switching in the Plex player settings (I haven't tested it).

Some other people reported that the beta android Plex player no longer has this issues, so we just need to wait it out (or sign up for the beta).

Lastly, and this is what I've done at home, is I just use SPMC, and use PleXBMC add-on and watch videos that way (which have handled audio passthrough just fine (with some modification to the default settings of course)).

Be sure to follow up if you find a work-around!

Andrroid

Just to be clear:

AC3 5.1 passes through from TV -> receiver just fine

AAC 5.1 downmixes to stereo

Correct? And it shows as direct play.

This tells me that the TV is sending a stereo signal to the receiver. Which means the TV doesn't support AAC 5.1.