Since tvOS 18 update Apple TV 4K and Apple TV HD output only stereo despite 5.1 selected

I didn’t notice until I checked that all the audio coming out of Apple TV was stereo PCM even though i specifically selected Dolby 5.1 and that it was working previously with my Sonos Beam plus One surrounds. After trying to reset the Apple TV and playing with the TV settings nothing worked. I decided to re-run the Sonos tuning and finally got it to output Dolby 5.1 again. I’m on tvOS 18.1

This happened to me as well! I tried everything from turning off my ATV, factory reset, unplugged and plugged both power and HDMI, etc. YouTube TV works fine with DD 5.1 PCM but not Netflix, Paramount+, ATV+. I tried with my PS5 and all streaming services flawlessly switch to DD 5.1 PCM.

I spoke with Apple Support which escalated to the engineering team. The guy mentioned that they've had multiple reports of the same issue. I had to send in a video, photo of my settings and system diagnostics to Apple Support. He's going to get back to me by Wednesday with an answer, hopefully.

As a developer I have found that the SDK API function AudioConverterFillComplexBuffer has stopped working for EAC3 in tvOS 18. This means it is not decoding EAC3 streams that use this API. The same function worked correctly on tvOS 17, and continues to work correctly on macOS.

Perhaps this is related, perhaps it isn't.

I've reported this via the developer Feedback Assistant.

I don't know - it may be that what I am seeing is another symptom of the issue you guys are seeing rather than the cause. Or it may be completely unrelated. But there are enough similarities for me to smell a rat.

All I know is that in the streaming app I am developing I have found that before upgrading to tvOS 18 a DD+ 5.1 stream was being decoded perfectly fine but post tvOS 18 the decoder just stops without any errors. In technical terms, the decoder is meant to ask for more data to decode; it asks for the first packet, which I give it, but never asks for any more after that, so no output data is ever produced. This has nothing to do with HDMI or anything else, at this stage it simply doesn't decode the data to PCM, so it never gets as far as sending it to the TV (or re-encoding as Dolby MAT, or whatever Apple TV does these days).

It's the same story on iOS 18, by the way. However, latest macOS (Sequoia) continues to decode the same stream, with the same code just fine.

As I say, I've logged it in the developer feedback section, so let's see.

Updated the tvOS 18.1 beta and it's finally fixed! Hallelujah!!

I forgot to mention that the YouTube streaming app was never affected by the issue. If you can find a video to play using the YouTube app that contains 5.1 audio, but you can't receive its 5.1 audio, that that would appear to confirm that the cause of the issue is something other than Apple TV.

The issue is now resolved. Apple TV update today solved the problem.

I have had the same problem since the update. Support told me to do a firmware update on my receiver but no such update exists. I have a digital audio extractor because my surround receiver has HDMI pass thru only. I realize it is an older model but this is how it has worked for years. I know the problem is not with the extractor because I hooked up my Gen 1 Apple TV the same way and I had 5.1 surround. I used to work for a company called Tweeter Home Entertainment and I own pretty nice gear. The only thing that changed in my scenario was updating to OS18. Very frustrating.

I wonder whether disabling Change Format and re-enabling it then making the Dolby Digital 5.1 choice might be needed. If the TV automatically senses the audio input, then maybe it should be restarted also.

I have spent an afternoon trying to figure out why some apps only output sound in stereo. 

ITVX and BBC iPlayer only output in Stereo on Apple TV, yet those apps on the Android TV will decode as DD + DSur on the Denon AVR

Some movies on Netflix will be "Multi-In" on AppleTV, but play in DD+ +Dsur on AndroidTV. 

I've tried: 

• changing physical connections from ATV > Philips TV > Denon AVR to ATV > Denon AVR > Philips TV to rule out issues with eARC. This is not the issue. 
• Running TVOS 18.2 and no this doesn't work.
• factory resetting ATV - no this is still the same. 

This is crazy - the AppleTV used to work and now the update has broken my setup. I'll have to use the AndroidTV on the Philips TV instead - that works with eARC. 

Come on Apple sort this out.

Apple Support followed up to tell me that the engineers believe it most definitely a software problem, not a hardware problem (as it worked perfectly before). Expect it to be fixed the next update.

same here, the setting i used forever was to force 5.1 but with tvos18 the apple app audio streams only in stereo.

interresting is that when using the remote play app (don’t know the real name, the app the lets you stream video from your home network, in this case a mac mini) the video’s are in 5.1, so it’s not a hardware connection problem

Good thing, the more people contacting them the more they'll work on it..

However, I don't think there's any fix for this besides another update of the tvOS... (Not counting hot-fixes that requires other Apple hardware products...)

My guess is that re-encoding from Dolby atmos to dts 5.1 is broken in tvos18 since streaming of original dts 5.1 is still working