Minicarter,
I just updated my Plex server to the latest Version 1.21.1.3830. Unfortunately, no change. Still transcoding 7.1 AAC to MP3 for me.
What’s weird is 5.1 AAC transcodes just fine to AC3 for me. It’s only my media with 7.1 AAC that seems to be having trouble. Just wondering do you have any 7.1 AAC you can test to see if it transcodes to MP3 as well?
Here’s another thread about this as well: Roku transcoding AAC 7.1 to Stereo MP3?
It’s happening with my 5.1AC3 converting to MP3 stereo instead of AAC and causing an audio lag issue - older version of server didn’t transcode to MP3 for Roku. It looks like you have good reference info here with the additional logs.
Thanks guys.
@Insomnic_1 just to be sure I understand. You have exactly the same problem?
@flickyourbic I don’t think ac3 is stereo. You’ll need to force your TV to take stereo, for example, which will force the plex to transcode in AAC or MP3.
If I force my Roku based Plex client to transcode AC3 or EAC3 5.1 audio into stereo, it transcodes it into an MP3 stream and I experience a gradually increasing audio lag (that’s when I noticed the transcoding to MP3 oddity). In the past, Plex has always transcoded to AAC for stereo and had no problem. I didn’t even know Plex would transcode to MP3.
I don’t have any 7.1 audio streams to test.
There is another issue with recent Roku update (not Plex but Plex is impacted) where AC3/EAC3 in MKV containers has a noticeable delay when direct play is enabled so I have been fiddling with some of the audio settings and know it was transcoding to AAC stereo before the recent Plex server update because that transcoding to AAC stereo was part of a workaround fix/testing for that AC3 audio bug.
Plex transcoding to stereo sometimes works better than letting my TV downmix to stereo so I was forcing the stereo transcoding by setting my Roku to “stereo” only mode. I have now set my Roku audio to DD setting so Plex now sends the AC3 5.1 stream to play without transcoding to stereo to avoid the MP3 stereo bug (letting my TV handle downmix now) and I can turn off Direct Play (but leave direct stream enabled) to get around the AC3/EAC3 5.1 audio lag bug… but it sounds like for folks with 7.1 those work arounds aren’t really working because it still wants to transcode 7.1 to stereo MP3 instead of AC3 5.1. So many audio bugs at once! 
Definitely a server side change from recent update causing this behavior. I can’t think there’d be any reason to use MP3 audio over AAC so I don’t know why this would be triggered except as an accidentally introduced bug.
Minicarter you’re not the only one, my friend. This issue has been driving me bonkers since the update for Linux was pushed. I’m using Roku Ultras, all wired ethernet, and after running the update for Ubuntu last week, my audio is coming through as stereo mp3, which I’m okay with, but the now there’s a noticeable sync issue between audio and video that worsens over time. I let it go on one movie and after about an hour it was comically bad. Never ever had this issue when the server was converting my audio for my Rokus to AAC stereo. So I’ve been scouring the web trying to find a fix and that’s how I stumbled here. I also posted this at Reddit but nobody responded.
Anybody know where I can download older versions to roll back my server? I will happily go back to pre-December 2020 versions to get my audio and video back in sync…
Although they aren’t linked directly on the site after newer versions are released, previous versions can still be downloaded. Grab a current download link from downloads page and replace all occurrences of the version string with that of a previous release. The last release in November was 1.21.0.3616-d87012962. You need the full version information (including the extended build information after the hyphen). More previous release version information can be found on the Plex Media Server announcements page.
Ah, ok. I’ll try to give it a shot.
Come to think of it, I don’t remove my downloaded files each time in Ubuntu after I grab an update. Might check there first.
From now on, I’m saving the download files! This update sucks!!!
I just wanted to chime in and say I also had this issue with a Roku Streaming Stick +. Audio was being transcoded to MP3 instead of AAC and created a delay/sync issue. I rolled my server back to 1.21.0.3616 and it resolved the issue. Audio is now being transcoded to AAC properly. It seems that something in the last few versions introduced a bug that needs to be resolved by the Plex team.
@Labrat2012, are you running Linux? I have still been googling (won’t have desk time to try this until tomorrow), and found one other thread where somebody said it’s a Linux thing. Just curious if true.
My next challenge if I do successfully roll back is figuring out how to remove Plex from my apt registry. I stuck it in there so I could update Ubuntu and Plex simultaneously, but with sucky updates like this, I want to be able to update them independently going forward. Just need to remember how I did it!
I’m running the server on Windows 10. I found another fix for the issue after posting on Reddit. Here is the post. There is a fix in the replies that works with the latest server version. I needed to modify the “ac3” part of the fix to “aac”, but it worked. I’m not sure if it applies to Linux.
I grabbed the Linux download link, replaced the version and build number with the ones provided here for the update at the end of November, and it worked beautifully. I’ll sit on this version until the release notes for subsequent updates indicate they fixed the AAC/MP3 transcode confusion, and fixed the audio/video sync delay problem.
Thanks for the help, everyone! You are lifesavers! Plex has been a godsend in this awful year we’ve had, so having it break was extremely irritating.
I am seeing not only Roku clients but also LG clients get transcoded to MP3 as well. How annoying.
I see people saying they are rolling back to the last update in Nov. Is that for sure the last one that worked correctly for this issue, or do we know the exact one that caused it? I would like to roll back only as far as the issue, and there have been 6 releases since the last November release. Anyone know for sure which one introduced this amazing feature that transcodes to MP3 on Roku/LG?
I’m glad I’ve found this thread, I too am having Audio sync problems with a Roku Streaming Stick+, which I am pretty certain only started happening in the last couple of weeks. I certainly did some server upgrades but annoyingly it also coincided with the Roku updating to 9.4.
My Live TV audio is transcoding to MP3. Now i’m not exactly sure what it was doing before but at least this looks promising to explain my problems. I will try downgrading to see if I notice any difference.
For reference I had also come across this thread (Audio out of sync) about audio sync problems on Roku, but i didn’t have any issue until the last couple of weeks whereas that thread is a couple of years old but still open.
Just as heads up, on Roku there is a 9.4 Roku OS bug with AC3/EAC3 audio being out of sync as well. A few other posts about that and if happening to you should be reported to Roku if you’re experiencing it.
There are essentially two audio sync/lag issues with Roku currently:
Issue one is a Roku bug and a work around in most cases is to turn off Direct Play, leave Direct Stream enabled, and make sure your Roku is setup with the right audio settings (typically the Audio->HDMI and make sure auto-detect is working, or you’ve manually selected appropriate supported options (DD, DD+, DTC or Auto-Passthrough). This fixes the audio delays for now.
Issue two seems to be from a recent Plex server update transcoding to MP3 stereo instead of appropriate AAC\AC3 supported formats like it did previously and thus getting some delay and impacts not just Roku.
Just wanted to give you a heads up since I’ve been seeing some folks get hit with one or the other without realizing there are two different bugs with similar results.
Cheers, I am in the MP3 transcoding bug camp by the looks of it. When I experience the issue I am not direct playing. It is Direct Stream for the video and transcode to MP3 for the audio.
I’ve tried turning it off and every other setting to rule them out every possibility anyway. I can’t wait until I do walk into the other problem though, as it is bound to happen lol.
To follow up on my previous post. I have now downgraded my plex server to 1.21.0.3616 as @Labrat2012 did a few posts back (Cheers for that heads up). It has resolved the issue for me too! Audio is now transcoding to AAC instead of MP3 and I am no longer having audio delay issues on Live TV. I can now rule out the jump to Roku 9.4.
Please fix this Plex!
Hmm I noticed this too on my Roku and Chromecast 3rd Gen. Thought it was a bit odd! Downgrading the server version fixed it for me too.
I just got one of those new Chromecast Google TV dongles. In my specific situation I set the audio setting on the Google Chromecast to manual Dolby digital because that is what the TV’s optical port will pass out to my Logitech 5500s. Plex is successfully transcoding AC3 audio. This is Chromecast TV dongle going in HDMI to the TV and the TV is passing out Dolby digital 5.1 AC 3 to the Logitech 5500s.
It is correctly transcoding streams to AC3 5.1 where the Roku was not with the same exact configuration. I see some other people are having trouble with Chromecast but probably not this exact same one so basically Plex needs to fix audio profiles I assume???
We got a comment on the other Roku AC3 bug (not a Plex issue) from a Plex Employee so maybe the holiday break is over and this will get attention as well. 
