Sudden Strange Audio Channel Mixing for Opus 5.1

[squaven 3]

The "Emby for Android TV" app has recently been outputting very strange audio channel mixing, specifically for Opus-encoded surround audio. All center channel audio for voices and sound effects comes out of the right channel speaker and surround seems to come out of center and left channels. This was not a problem a week ago.

Recently, I started seeing pop-ups saying I should switch to "Emby for Android" for the latest features, when I attempted to install and use it instead of "Emby for Android TV", I noticed these same problems with Opus audio on the Android app. Because of these problems I switched back to the Android TV app and the audio problems were resolved.

Now, as of a few days ago, both apps seem have the exact same problem. When I select "Problem with Playback" and it switches to transcoding to Surround 5.1 audio, everything comes through as expected. It is only when playing "OPUS (direct)" when the audio channels are all mixed up. Playback is perfectly fine when going through the Emby for Linux Beta on my laptop playing as OPUS 5.1 direct.

Did something change recently with the way these streams are handled?

Thanks for any help you can provide.

[Luke 43389]

 

Hi there, let's look at an example. Please attach the information requested in how to report a media playback issue. Thanks!

 

[squaven 3]

embyserver.txt

Here is the embyserver log, trimmed to within a few minutes of the problem. (Problem was replicated at approx 18:35 PDT with user BrandonAdmin, watching Reacher S1E1). I also followed the steps to upload logs from the Emby Android TV app, sent at approx 18:36 PDT (21:36 EDT). All background sounds/music sound like they are coming from the left channel. All foreground sounds, voices, etc sound like they are coming from the right channel.

[ebr 16937]

Hi. Unfortunately, all your playback got compressed in your app log so I can't see what was going on but, if it is direct playing, then this is either a problem with the internal decoder on the device or the encode of the media itself.  How was the media created?  Have you tried remuxing or re-ripping it?

Opus is notoriously problematic on just about all devices other than browsers, I believe.

[squaven 3]

First off, thank you guys for looking into the problem. I understand where you guys are coming from on the OPUS compatibility problem. At this point I'd love to just go back and re-encode from source to AAC but this will take time and effort so I'm hoping there's some way to return to previous functionality in the meantime.

I suppose, I was hoping the answer would be either 1) We just pushed an update where we now play direct when we used to transcode by default (in which case, can a toggle be created to auto-transcode like already exists for AAC surround) or 2) we just pushed an update to media playback to bring Android TV in line with Android and it broke something.

I'd love to blame my AV receiver or NVIDIA Shield, but things seemed to work a few days ago and, at that time, I could directly point to different results between "Emby for Android" and "Emby for Android TV" with all other devices and settings being the same.

[squaven 3]

So, to respond to ebr's questions:

The files were originally created using MakeMKV. The audio track was originally DTS-HD and was transcoded into OPUS using Handbrake to reduce file size. I have done some tests, transcoding into EAC3, AAC, and OPUS.

The problem only appears in the OPUS transcode and persists even after re-rip and re-transcode. The problem also affects not only newly transcoded media, but any media using OPUS surround, even media that has played back perfectly for years.

The problem seems to be exactly that the center and right audio channels are flipped. The center speaker is playing background and surround and the right speaker is only playing voices and foreground. DTS-HD, EAC3, and AAC all playback as expected.

I am going to see if my friend can run a test on his Jellyfin server to see if Jellyfin can handle OPUS 5.1. I know that 5.1 surround is perfectly acceptable according to the spec.

Is there anything else we can do?

[Luke 43389]

Hi.  Can you try searching for our standard android app (Just "Emby" on Amazon and "Emby for Android on Google) on the same device's app store and see how that compares?

Thanks.

 

[squaven 3]

Very good but very strange news. The "Emby for Android" app now appears to work and plays OPUS 5.1 audio as expected. This is the exact opposite result that I saw several weeks ago, when I first tried the Android app and originally noticed the problem. Because of the original problem showing up on the Android app, I switched back to the Android TV app. Now, it appears that the Android TV app is broken and the Android app works. Very strange. Hopefully there is some difference in the way the two apps stream out that can give some clues to the strange behavior.

[Luke 43389]

Great, that's helpful info to go on. Thanks.

[squaven 3]

No, thank you! I really appreciate that you guys are so responsive.

[ebr 16937]

6 hours ago, squaven said:

transcoded into OPUS using Handbrake to reduce file size.

How much does that actually save?

[squaven 3]

Actually, quite a bit, depending on encoding options. I'm having trouble finding exact stream sizes for my test files currently, but to give an idea of files I created to test this problem:

Starting with a single Blu-ray episode at 15GB uncompressed, firstly, the video re-encode to h264 q23 makes the biggest difference by far. But comparing the final sizes using various audio formats (when given bitrates that are close enough to transparent for my ears at least):

Audio Codec	Final File Size
DTS-HD (Passthrough)	2.0 GB
EAC3	1.3 GB
AAC (5.1)	860 MB
Opus (5.1)	800 MB
AAC (Stereo)	780 MB

Over the course of a 200 episode-long series or over the course of hundreds of movies, it adds up quickly and can mean real savings (especially with today's hard drive costs). There isn't a huge difference between Opus and AAC for 5.1 surround in terms of file sizes, but everyone seems to agree that AAC is also not extremely compatible for surround and, based on the receiver/tv, usually downmixes to PCM stereo. So my only real option for perfect compatibility is AC3/EAC3 or just doing passthrough. Those get up to unreasonable sizes for large libraries.

An unfortunately, there is the problem that I made the decision 2-3 years ago to go Opus (of course there's always so many people saying "This is the way of the future! Everyone will be going Opus!") so most everything is now already transcoded down. I could probably go to AAC over the course of 6 months to a year of work. But even then, it'll probably take another couple hard drives to grow my ZFS pool.

Edited October 14 by squaven
Realized a slight difference in bitrate, leading to less correct file sizes