What is ARC and eARC?

In plain language

Audio Return Channel lets a TV send its own audio — from its apps, or from a device plugged directly into it — back to an AV receiver or soundbar over the existing HDMI connection.

Plain ARC has limited bandwidth: compressed 5.1 at best. eARC, introduced with HDMI 2.1, has far more, enough for uncompressed multichannel PCM, Dolby TrueHD and DTS-HD MA, and therefore for full-fat Atmos rather than the compressed version.

Why it matters in your setup

Both ends must support the same version, and it has to be enabled on both — it often is not by default. The port matters too: only one HDMI port on a TV is usually the ARC or eARC port.

One trap catches people repeatedly: Atmos over ARC needs a cable that supports 192kHz audio. A cable can carry a 600MHz video signal perfectly and still fail on the audio return, which makes the fault look like a device problem.

What the DR HDMI 8K does with it

ARC runs between your TV and your audio device, so it is not the DR HDMI 8K's job. Where the unit helps is on the outbound path: it controls exactly which audio formats are advertised to the source — L-PCM, TrueHD, DD+, DD, DTS-HD MA, DTS — so you can test whether a missing Atmos track is a capability that was never advertised rather than an ARC fault.