I have the following setup:
HARDWARE
- Philips 55OLED856/12
- AppleTV 4K (2nd Gen)
- Sonos Arc, Sonos Sub, 2 Sonos One’s as Surrounds
CONNECTIONS
- Sonos Arc connected via HDMI-2 - eArc
- AppleTV Connected to HDMI-1 - Arc
TV Audio Settings
- Audio Output - HDMI Sound System
- eARC - Automatic
- Digital Out Format - Multichannel (bypass)
AppleTV Audio Settings
- Audio Output - Receiver Speakers
- Audio Format - Auto
- Audio Mode - Auto
When playing video from AppleTV that is in DolbyAtmos/DolbyVision all the sound is sent to the correct channels. When playing video that is not in DolbyAtmos (normally from Disney+, Netflix or Amazon Video) the audio is not being sent to the correct audio channels. It seems that the Voice Audio that would normally come from the centre channel is being sent to the rear surround channels.
I have tested and this appears to be only be happening when the video/audio is coming from the AppleTV. I have tested Netflix and Disney+ from the AppleTV - TV - Arc and the audio that is sent to the Arc is passed as Multichannel PCM 5.1. When this happens the audio for Voice that would normally be played via the centre channel is coming though the rear surrounds. However, if the audio passed from Netflix, Disney+ apps is DolbyAtmos the sound is coming correctly to the right channels.
I tested the Netflix, Disney+ etc apps that are natively installed on the TV and the Audio sent from the same shows is sent as Dolby Digital Plus 5.1, (not Multichannel PCM. 5.1) and this audio comes through to the channels correctly.
The problem seems to be with the encoding of the Audio when it is received from the TV eARC as Multichannel PCM 5.1, as the audio (voice) channel are mixed up and played through the rear surrounds.
I am not sure if this problem is with the TV or how the Arc is determining Multichannel PCM 5.1.