Most puzzling AV faults have one of two causes: the source and display disagree about the video format (EDID), or the content protection handshake fails (HDCP). Knowing how both work makes troubleshooting much faster.
What EDID does
EDID (Extended Display Identification Data) is a small data block a display sends to the source to say which resolutions, refresh rates and audio formats it supports. The source then picks a format from that list. With one source and one display, this happens invisibly.
Where EDID goes wrong
- Mixed displays: when a splitter feeds screens with different capabilities, the source may choose a format one of them cannot show.
- Switching: when a KVM or switch changes ports, a computer can briefly lose sight of the display and rearrange windows or drop resolution.
- Long chains: extenders and converters can pass along incomplete EDID data.
EDID management solves this by giving the source a fixed, known-good EDID. Common methods are copying the EDID from a chosen display, selecting a built-in preset, or using a dedicated EDID feeder (emulator) that sits in the signal path.
What HDCP does
HDCP (High-bandwidth Digital Content Protection) encrypts video between devices so protected content cannot be copied in transit. Every device in the chain must support a compatible HDCP version, otherwise the source may refuse to send the picture or reduce its quality.
Practical rules
- For 4K protected content, plan for HDCP 2.2 across the chain. HDCP 1.4 equipment is generally fine for HD content.
- Count the displays: each one behind a splitter is another HDCP device the source must authenticate.
- If a picture appears on some screens but not others, check EDID first, then HDCP versions.
Looking for a fix in hardware? Browse our EDID feeders, boosters and converters.