Cable first, EDID second.
Start by isolating the variable.
DR HDMI 8K can give the source a known EDID and provide a stable diagnostic point in the chain. That is useful when testing whether behaviour changes with a controlled capability set. It cannot make a cable carry a signal beyond the cable’s electrical or optical capability.
What DR HDMI 8K can — and cannot — tell you
For full-bandwidth 48Gbps operation, the DR HDMI 8K manual explicitly recommends appropriate certified/tested HDMI cabling. With active or fibre HDMI, also follow the cable manufacturer’s direction and power requirements.
Important: If a lower-bandwidth mode works but a higher-bandwidth mode fails, investigate the entire link before assuming EDID is the cause.
A practical test order
- Confirm the source, display/AVR and cable support the target format.
- Start with a known working lower-bandwidth mode.
- Read or copy the downstream EDID.
- Present a known predefined or deliberately modified EDID to the source.
- Change one capability at a time and observe the result.
This approach is more useful than changing the source, cable, AVR settings and EDID simultaneously because it keeps the test repeatable.