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Troubleshooting

Installation issues with HDMI-connected systems are rare, but when they occur, they typically fall into one of two broad categories: connectivity issues and interoperability issues. Problems with physical connectivity can usually be resolved by selecting the right cable and distribution gear for the job, as discussed in Connecting HDMI Devices and HDMI 101. Interoperability problems, on the other hand, can sometimes be more challenging to troubleshoot and resolve.

EDID Implementation Issues

One key area of interoperability for HDMI-connected devices is the ability to effectively communicate EDID data via the DDC channel. If the sink device (the HDTV or projector) has its EDID ROM coded incorrectly, or if a source or repeater device fails to read it properly, the system will fail in its attempts to auto-negotiate the proper video and audio modes. Symptoms of this problem include incorrect color space and/or the wrong resolution. Some installers take a small, reliable 1080p set along on installation calls to troubleshoot for this – if it doesn’t look right, the problem is most likely in the source device; if it looks good, the problem is probably in the sink. Regardless of which component is to blame, the issue can probably be resolved with a firmware update from the manufacturer.

HDCP Implementation Issues

The HDCP handshake is critical to components working together properly in an HDMI/HDCP enabled system. Problems tend to arise in two areas of implementation, and nearly always in the source device. First, sources need to support an HDCP function called “authenticate forever.” In other words, the source must consistently send a signal inquiring if its HDMI input is selected, even while another input is in use. If a source device times out and stops inquiring, an HDCP authentication failure will probably result. Second, source devices need to properly implement the HDCP repeater function if there’s going to be a repeater device installed in the system, i.e., an A/V receiver. Otherwise, switching between source devices can result in an HDCP authentication failure. Once again, a firmware upgrade to the source device will probably solve the problem.

Interoperability Issues

The HDMI licensing group is actively working within the industry to educate on these issues and help make product interoperability a top priority for everyone. In the spring of 2007, Digital-CP (the company that licenses HDCP), released a compliance testing specification for HDCP. HDCP testing is now required for all products that undergo HDMI testing when the product incorporates HDCP technology. Industry initiatives are also helping to address the problem, such as “PlugFest” events, where manufacturers come together and self-test their devices for interoperability. There are also outside testing and certification programs, such as the Simplay HD program, that are designed to provide interoperability and performance measurements and help ensure wider interoperability.