Apple TV 4K not auto switching for stereo content after playing 5.1 audio

Apple TV 4K 2022 (gen 3)

Philips PUS7304 TV

Sonos 5.1 Setup (Beam + Symfonisks + Sub) through HDMI ARC


When playing content (tested on Netflix and Amazon Prime apps) that only has stereo audio, as long as this is the first content played after the app is started, the audio plays correctly and I can see in the Sonos app 'Stereo PCM'. If I then play content with 5.1 surround, the audio plays correctly and the Sonos app changes to show 'Dolby Digital 5.1'. After playing 5.1 content however, going back to content with only stereo audio does not revert to 'Stereo PCM' output, but remains showing as 'Dolby Digital 5.1', and is audibly different to the correct Stereo PCM output. The sound is louder and wider, but voices lose clarity sounding muddier, and there is also a small but noticeable lip sync issue.


The only fix I have found so far is to force close the app on the Apple TV, reopen, and quickly navigate to the desired content without allowing any other content to autoplay a preview, as this again will set the audio output to Dolby Digital 5.1 and prevent correct stereo output.


Apple TV is set to Auto for Audio Format, however this issue also happens when set to 5.1.

TV is set to passthrough (Multichannel bypass) for audio so is sending the originally received audio to the Sonos.

I have tried Audio Mode Auto and 16 bit with no difference.

I have tried Apple TV Match Content video settings on and off with no difference.

Have rebooted Apple TV, Sonos, and TV with no change.


I have read many posts about people only receiving stereo audio or no audio instead of 5.1 but haven't found anything about stereo audio being incorrectly output as Dolby Digital 5.1.


Any ideas?

Posted on Aug 15, 2023 4:18 AM

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3 replies

Sep 2, 2023 6:52 AM in response to B80BBY

Apple TV uses Dolby MAT to pass multichannel PCM audio with Atmos and Surround Sound metadata over HDMI to your surround sound processor. I believe this is a format and approach meant for video game consoles so that you have a more seamless experience with menu sounds and so forth. When you play content on Apple TV your surround sound processor / receiver is not being passed the original audio bitstream to let the surround sound processor decide if its 5.1 or 2.0 to decode and play out to the correct speakers. Instead, the bitstream is being decoded inside Apple TV and incorrectly (in this case) mapped to a 5.1 PCM and that is passed along to your processor along with the Metadata. This is why you have a stereo source showing as 5.1 content on your surround sound processor. Your receiver does not know that the center channels and rear channels have no audio on them and this is why it only plays from your L and R speakers. I wish Apple would pass through content bitstream to let your receiver deal with the content and during menu interactions encode their own AC3 signal for the receiver. So my workaround for this - if you know you are watching a show which is stereo source, you go into your Apple TV audio and video settings, set the Audio Format Change Format to On, and New Format to Stereo. Now your stereo source show will be correctly mapped to a stereo PCM format that your receiver can correctly deal with depending on your speaker configuration. If the Stereo source is surround encoded then your receiver will properly use its Dolby Pro Logic, DTS: Neo 6 or DTS: X processors to emulate discreet surround from a stereo source.

Sep 20, 2023 7:46 AM in response to mcsound83

Thanks, I'm aware the Apple TV does things differently compared to other streaming devices with regards to sending the audio. The point is that it's doing it inconsistently and erroneously in this case. If the first content you play from an app is simple stereo, it plays it fine, but if you play content with any Dolby Digital encoding it seems to hook onto a Dolby Digital 5.1 format and won't drop back down to output only stereo, which sounds spatially wrong and introduces a small but noticeable lip-sync delay.


The work around for me is to quit and relaunch the app before playing content I know is only stereo encoded, but it's a clunky solution (as is changing the audio output to stereo selectively). It's a bug and it needs fixing, not more workarounds.

Oct 7, 2023 6:56 AM in response to B80BBY

I am having the exact same issue, but only with one app. I use the Channels DVR app to watch network(cable) tv. Ever since TVOS 17 I am getting the same problem with this app only. Netflix, Prime, Hulu etc all work perfectly but Channels gets stuck in 5.1 and nothing will release the Dolby flag except a full force quit of the app.

Apple TV 4K not auto switching for stereo content after playing 5.1 audio

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