HDMI signals

HDMI handshake

How a source and a sink agree before a picture appears

A handshake that goes wrong shows up as a black screen, a flash of snow, or a picture that appears and then vanishes. Knowing which of the three steps failed is most of the repair, and the Diva reports each of them.

HDMI handshake is not a term in the HDMI specification. It is the name installers give to the sequence a source and a sink go through before any video is carried: the sink asserts hot plug detect on pin 19, the source reads the sink EDID over the DDC lines, the source picks a format that the EDID says is supported, it starts the TMDS clock and data lines, and if the content is protected the two ends authenticate over HDCP. Only when all of that has finished does a picture appear.

Each step can fail on its own, and the symptom tells you which. With no hot plug the source never even looks, and reports that nothing is attached. A bad or truncated EDID read sends the source back to a safe format, usually 480p or 1080p60 RGB. A failed HDCP authentication gives a black or snowy screen on protected content while menus and unprotected apps look perfectly normal. A marginal TMDS link gives sparkles and dropouts that come and go with cable length.

What the HDfury Diva does in the handshake

The Diva is a repeater, not a piece of wire. It terminates the link on each side: its receiver completes the handshake with the source, and its transmitters complete a separate one with each sink. The OLED default info page shows that happening. When an active input is connected the page names the port, for example IN1, then completes the HDCP and EDID handshake with that input, and the signal information appears alongside it once the exchange is done.

That separation is what lets the Diva fix things rather than only pass them on. Fifteen HDCP 1.4 and 2.2 engines decrypt at the input and re-encrypt at each output individually, to 1.4, to 2.2, or not at all if the source was never encrypted, so an HDCP 2.2 source can reach a display that was never HDCP 2.2 compliant. The EDID the source reads is whichever of the five EDID modes you selected in the EDID section, which is not necessarily the one your display sent.

When it does not complete

• Compare the IN row with the EDID row for that output in the INFO section. A source stuck at a lower format than you expect is answering an EDID, not an output stage.
• Click ISSUE HOTPLUG in the CONFIG section. It sends a hotplug event, which performs a soft reset of your setup and makes both ends start again.
• Put any HDMI or HDCP 1.x device on TX1. That output downscales the channel to 1080p SDR and encrypts it to the level such a sink expects.
• Check the cable. Any cable in the chain has to support 18Gbps if an 18Gbps source or sink is connected to it, while TX1 and the audio output never exceed 1080p, so ordinary high speed cable is fine on those two.

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