HDMI Connections

Surviving HDCP handshaking problems

HDMI (High Definition Multimedia Interface) connections promise to be the easiest and best performing connection between high definition devices such as Blu-ray Disc players or HD-DVD players and new flat panel displays.

One advantage to HDMI is that it provides both video and digital connections in one lead, eliminating cable clutter. Another advantage to HDMI is that it removes signal conversions that could downgrade quality. For example, HDMI connections eliminate the need to convert digital video signals to analogue and then back to digital for processing in a flat panel display. Another advantage is that the HDMI high bandwidth capability offers greater picture resolution and multi channel audio. Seems like an excellent connection solution, right?

The sting in the tail? HDCP.

High bandwidth Digital Content Protection (HDCP). HDCP is a type of Digital Rights Management that controls digital content as it travels through HDMI connections; its purpose is to stop content piracy. The HDCP specification is managed by firmware which is built into devices. It requires devices connected via the HDMI cable to perform a communications handshake across the HDMI connection every few seconds. If the devices don't or can't handshake, that is they can't authenticate, then the device connection is disallowed, and all images and sound are cut off. This level of device authentication requires all devices to be talking the same language, at the same rate, using the same encryption methods.

Unfortunately, It seems that not all manufacturers have had full access to the HDCP specifications until recently; therefore there are some variations in how different brands have implemented the HDCP specification. Needless to say, the Hi-Fi / Home Theatre industry is having some issues with compatibility.

The problem for retailers and consumers can be the lack of manufacturer support when different brands are mixed in the same overall system (there can be some real advantages in doing this). If the communication between devices fails, then manufacturers may not be willing to take the steps to support a failure between their device and another manufacturers device; after all their device probably works as they intended it to.

Device authentication problems can also be caused by using non-certified leads in the market place. Without proper certification there is no guarantee that the HDMI specifications are met, and remember HDCP runs across the HDMI connection.

What to do?

I have no doubt that these specification and compatibility issues will be resolved in time; but in the mean time I suggest wiring all difficult access components (e.g. wall mounted plasma or LCD) with both analogue and HDMI connections. The analogue connections are a good backup, allowing the devices to continue to work even if the HDCP handshake fails.

Some more practical tips:

• Consider purchasing your equipment from a specialist dealer. Dealers have the knowledge and experience to guide you through these sorts of technical mine fields. We can provide time and money saving advice on product selection and setup.
• Use certified cables. Again, a dealer can help you make the right selections.
• Do research on manufacturers to find out what kind of support they provide and what kind of claims they make about their HDMI and HDCP compliance.
• Talk to friends who have worked through this problem.
• Use the Web and visit relevant forums to educate yourself on the topic.

Rotel have written an excellent article on the topic. Read the Rotel article (pdf 280KB).

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Email or call us for advice.

- Terry Anderson