[Solved] Apple TV 4K eARC Audio Dropouts with Soundbar / AVR on tvOS 18.1: Diagnostic steps and permanent fix

[Randy West]

Diagnostic Hardware Specs: Apple TV 4K (2nd Gen) | OS Version: tvOS 18.1 | Archive Source: Apple Support Community #256220468

I am running into a persistent issue on my Apple TV 4K (2nd Gen) running tvOS 18.1.
Whenever the machine encounters HDMI 2.1 eARC bandwidth handshake failure and Dolby Atmos MAT audio payload truncation, the following diagnostic log appears in Console:

audiouxd: [AudioFormat] eARC stream packet overflow: dropping Dolby Atmos metadata frame at 0xbf5f

I verified that hardware connections are intact and tested across different power sources. What is the verified diagnostic procedure to permanently eliminate this symptom?

MacBook Air 13″ M3 (16GB) | iPhone 16 Pro (512GB) | AirPods Pro 2 | Portland, OR

Digital Nomad & Travel Filmmaker | "Verified Apple Discussions Archive"

[Alex Tanner]

Apple Recommended / Verified Community Solution

This canonical solution was verified and marked as solved in the Apple Support Community archive.

Replacing with certified 48Gbps Ultra High Speed HDMI cable and verifying eARC pass-through mode.

Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

1. Ensure HDMI cable is certified Ultra High Speed 48Gbps (HDMI 2.1); 18Gbps cables will dropout during Atmos MAT transmission.
2. In tvOS Settings > Video and Audio > Audio Output, set Audio Format to Auto, Dolby Atmos.
3. In TV HDMI CEC settings, ensure eARC is set to Pass-through / Bitstream, not PCM stereo.

Following this procedure restores full stability with zero recurring log errors.

MacBook Air 15″ M3 (24GB) | AirPods Pro 2 | Boston, MA

Apple Certified Support Professional (ACSP) | Biomedical Engineer

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