The HDMI Handshake is the process by which the sink and source agree. They both find they can carry the HDMI signal with high bandwidth. Perhaps the most notorious blunder that might happen in this pathway is with the HDMI “Handshake”. Many factors can cause an hdmi handshake problem. The following information may be useful when debugging or optimising the HDMI handshake.
Both source and sink must support the HDMI 1.3 specification and higher. Most equipment supports this specification out of the box, but some older devices may not be able to accept any version of 1.3 and higher due to their hardware limitations. Also, not all equipment can support Deep Color (the current highest resolution at 30 bit/px), so check if your device supports this feature if you need it to work correctly on your setup.
What is a hdmi handshake?
The HDMI handshake is a series of signals sent by the source and the sink when they find that they can carry high-bandwidth video. The data is encoded in payloads called Object Descriptor Blocks (ODBs), which come in pairs. The first ODB describes supported data types, and the second describes what is supported for each type.
The HDMI standard dictates exactly how many ODBs there should be for each type and how many are needed to describe proper support for a feature. When two devices attempt to communicate over an HDMI link using a pair of these ODBs, the sending device must check its own supported video types against those of the receiving device.
How do I fix it?
When you switch your delivery device from one source to another, you must re-authorize and re-authenticate to transport the high-bandwidth HDMI signal. Once you have successfully switched, you will no longer experience a handshake problem. However, scenarios such as using a dual-link cable can cause the handshake to fail. A proper “deep” HDMI cable and an HDCP-compliant source are required to fix this issue.
A “deep” hdmi handshake cable has an additional wire that goes off the connector in addition to the 7-pin (or 4-pin if it’s a CEA-compliant source), which carries video. This extra wire is so that something between the source and sink can swap the ODBs before they are calculated. Microcontrollers in the cable are placed at a point where the source and sink can be close enough together but still separated by the additional wire.
The microcontroller will read data from sources that do not support HDMI 1.3 or higher and flip the bits around so that those devices can properly calculate them. If you have an “up-converter”, remember that it must also support the HDMI 1.3 specification to exchange ODBs with a “deep” HDMI cable properly. The handshake problem is further aggravated when using an up-converter, which will cause you to use a long cable because of its limited bandwidth capability.
Conclusion:
The HDMI standard is still being refined, and new versions are being released by the HDMI Forum every year. Because of this, it can be difficult to find fully compatible equipment that will work together without a handshake problem. However, these problems are becoming less frequent as technology improves.