Atmos ok but no 5.1 surround sound

Question

Atmos ok but no 5.1 surround sound

Hi,

I have just bought a new setup with Sonos Beam Gen2, TCL 4K eArc TV and Apple TV 4K.

Everything is up to date and Sonos Beam is connected thought eARC port. TV is configured on Passthrough for HDMI audio (or Auto but same result).

I able to read Atmos contents from Apple TV, I can see "Dolby Atmos" on the Sonos App.

But everything else (including Dolby Digital 5.1.) is played as PCM Stereo (confirmed in Sonos App).

I have to go into Apple TV parameter to change audio format and force Dolby Digital. In that case I'm able to have Dolby Digital on the Sonos Beam but Atmos is deactivated for next time and I need to switch back the parameter to auto in Apple TV.

I have read similar issues on Apple Community and I have contacted Apple Support, they told me that we are many in that case.

Changing audio parameter in Apple TV is forcing encoding to Dolby Digital which is resulting decrease of audio quality...

Do you have any fix for that? Or should I wait a software update on Apple TV?

Thanks.

Apple TV 4K, tvOS 15

Posted on Mar 8, 2022 5:06 AM

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Answer 1

Top-ranking reply

bgmeek

Level 4

1,243 points

Mar 8, 2022 10:43 AM in response to Docteurmicro50

Hmmm... It's odd that an advanced format like Atmos gets passed through but Dolby 5.1 is reduced to stereo. On my system, the Sony Soundbar reports "Atmos" with Atmos content, and Dolby Digital 5.1 content as "LPCM 5.1ch 48 KHz" (converted to 5.1 PCM multichannel as @Urquhart1244 said).

My guess is that your TCL TV isn't fully configured to communicate capabilities via HDMI CEC to the Apple TV. Your ATV4K appears to believe that the TV's two speakers are all it needs to deliver PCM streams to. I would dive into the TCL's settings menus to verify that all the HDMI CEC / automatic / advanced audio & video related settings are turned on for the TCL's HDMI port that the ATV4K is connected to. Likewise, I would confirm that the Sonos is set to communicate its full capabilities and is allowing all devices to control it via HDMI CEC.

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Answer 2

Urquhart1244

Level 10

146,686 points

Mar 8, 2022 5:17 AM in response to Docteurmicro50

Apple TV outputs 5.1/7.1 surround sound as PCM Multichannel (not stereo if the source video has more than two audio channels). PCM just means uncompressed. It works as intended.

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Answer 3

Mar 8, 2022 5:26 AM in response to Urquhart1244

Thanks a lot but why the Sonos is displaying PCM Stereo and not Dolby Digital?

I can hear the difference between this 2 modes....so I thing PCM Stereo in Sonos App is just Stereo 2.0 and not PCM 5.1...

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Atmos ok but no 5.1 surround sound

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