I noticed Yesterday that all of my plex movies that are encoded 5.1 are only playing in Stereo. I have test this with 20 different media as well as a couple of crackle movies
Model-Vizio M55Q7-H1
TV is on Firmware 1.20.18.9-1
Plex Version 5.24.1
When I play a movie and go to system information the TV shows Audio IN: stereo
So it seems to be the app causing the problem and not the tv itself
My Plex server is on version 1.24.2.4973
Any assistance you can provide would be appreciated.
It’s possible that the TV can’t decode the 5.1 signal your sending it so Plex is transcoding it to a stereo mix. What is the audio encoded in and are you playing it through the TV speakers?
I am running audio through HDMI ARC port to a Vizio 5.1 sound bar. The Encoding is ACC 5.1. TV Speakers are turned off. When I switch to my Disney + app on the tv it works properly and sound goes to 5.1. Also when I switch inputs to my DIsh Hopper Box I get proper audio as well.
This just started yesterday, so I know it has been working properly prior to that. It goes in the same timeline as when the Plex App was updated to 5.24.1.
I think your problem is that transporting AAC 5.1 over ARC is not technically possible. My understanding is that since very few things natively support multi channel AAC they are converted over to PCM when sent to your device, but in your case since you are using ARC and not eARC multichannel PCM can not be transmitted over ARC. So Plex transcodes that audio stream over to 2.0 AAC to make it compatible with your system.
So I just tested it and changed it from PCM to Direct and got the same thing.
ARC from what I understand can support 5.1 but nothing higher like ATMOS. It can Support DTS as I have it going from my Bluray player and getting DTS encoded sound.
ARC can support 5.1 if it is encoded in the correct codec. Multi Channel AAC (AAC 5.1, 7.1, ect.) has basically no support and has to be converted to PCM to work on devices that support PCM. It also has to have a viable transport path for said PCM signal. ARC cannot transmit multichannel PCM, that can ONLY be accomplished on eARC as far as I know. Hell my nearly $1k AVR doesn’t support multichannel AAC. It does support multichannel PCM through eARC though. I am fairly familiar with all this as my library is basically all encoded with AAC audio. If you wanted to test this, get a file that has AC3, EAC3, or something similar and see if it works.
Direct or Auto is most likely the correct setting for the TV’s digital audio output. Forcing things to PCM may result in Plex transcoding the audio if it is in another format. Also, as @Blkbyrd mentions, HDMI-ARC is limited to PCM 2.0. It will pass AC3/EAC3/DTS up to 5.1 channels.
As Blkbyrd suggests, play a video with Dolby Digital 5.1 or Dolby Digital Plus 5.1 audio. Both of those format should passthrough to the soundbar.
You can monitor playback via Plex Dashboard → Now Playing. It will show if the Plex Media Server is transcoding the audio to another format.
FWIW, the app doesn’t limit on the number of channels when deciding whether it can direct stream AAC. All the Vizio SmartCast TVs we’ve tested can handle at least up to 7.1 directly. How that ultimately gets passed to the soundbar is handled by the TV.
The one caveat is that if there is an error trying to play something (e.g. because there is something about the file the TV doesn’t like or if one of the audio settings is enabled and the TV can’t actually handle whatever was enabled), we’ll fallback to a transcode regardless of whether we thought we could direct play it initially.
Thanks all. So I have encoded a movie in AC3 5.1 and not AAC5.1 and it works fine. So there seems to be an issue with the Vizio M series TV. Most probably the latest firmware changes how it handle the AAC codec in 5.1 channels. As it now send it as stereo.
When I look at the Plex App and the Plex Server is shows proper AAC 5.1 but the TV is not handling that codec properly.
I know this is late but what is the model of your soundbar? I can check to see if it supports eARC. If it does then hooking it up through HDMI port #1 on your television should alleviate all of these issues as your TV supports eARC and therefore should have no issue transporting PCM multichannel audio to a compatible output. It looks like the only 5.1 sound bars from Vizio that support eARC are the M-Series and above.
Its an older Vizio V series Sound bar, but it is not causing the problem. Yesterday I troubleshot with Vizio, and we have determined that the last firmware for the Vizio TV caused the issue. ITs not only happening in Plex, but in Youtube, Paramount+ and Peacock streaming services. They are looking into see why AAC is only now encoding stereo and not the actual channels it is getting from the media My sound bar does not support EARC, but I am looking at upgrading the sound bar to the Vizio m51a h6 as it does support EARC and Dolby ATMOS. Not that I have any media in that format, but the older Sound bar does have some lip sync issues and I am hoping the new sound bar can fix that.
