Dolby Digital Plus (DD+) explained

The short explanation

Enhanced AC-3 improves on Dolby Digital: better efficiency, higher bitrates, more channels. Still lossy, but a clear step up — and crucially it can carry Atmos object metadata.

Where you run into it

Streaming Atmos is DD+ Atmos; disc Atmos is usually TrueHD Atmos. They are different formats doing the same job, and a chain can advertise one without the other.

That explains a common report: Atmos from Netflix but not from a Blu-ray, or the reverse. Two different capability flags, two different outcomes.

How the DR HDMI 8K handles it

DD+ has its own flag on the DR HDMI 8K with its own mode and sample rate settings, separate from the TrueHD flag. If streaming Atmos works and disc Atmos does not — or vice versa — comparing the two flags is where the answer usually is.