What is EDID, and why does it cause "no signal" errors?

EDID (Extended Display Identification Data) is the information a display or capture device sends back to a source to tell it what resolutions, frame rates and colour formats it supports. It's the handshake that happens silently the moment you plug an HDMI or DVI cable in — and when it goes wrong, it's the single most common cause of a "no signal" or wrong-resolution problem in video capture.

If the capture card's EDID advertises the wrong thing — say it only lists 1080i when you actually need 1080p60 — the source will dutifully pick 1080i, because that's all it was told was available. The fix usually isn't a cable or hardware problem at all: it's setting the card's EDID to match what you actually want the source to output.

This matters most with HDMI/DVI sources that read EDID once at connection time — if you change a setting and the source doesn't immediately switch, power-cycling the source after an EDID change is usually what's needed, since most devices only read EDID on connect, not continuously.