Issue link: https://www.e-digitaleditions.com/i/1156106
October/November/December 2019 I 9 High-bandwidth Digital Content Protection (HDCP) HDCP enforces program content copyright protection by encrypting the signal. To view the content, a successful authentication handshake and encryption key transfer between the source and the sink is required. HDCP restricts what the end user can do with protected content by limit- ing the number of simultaneous displays, disallowing recording or copying and disabling analog outputs. HDCP has evolved from Version 1.0 for DVI to the current Version 2.2 for 4K video. Since Version 2.0, HDCP has been interface independent, making it ubiquitous on all current AV interfaces: DVI, HDMI, USB-C and DisplayPort. HDCP can be problematic in complex AV systems. The HDCP handshake introduces a noticeable delay, which can be bothersome in AV systems containing video switchers. Switcher manufacturers have designed methods for eliminating switching delays by maintaining contin- uous HDCP authentication between switcher inputs and outputs, eliminating reauthentication during switching. Another issue is that HDCP specifications have evolved and newer sources may not work with older downstream equipment. The best rule is to ensure everything in the path conforms to the highest level of HDCP protection that will be encountered. For 4K video, that means HDCP 2.2. If this rule is overlooked, it is possible the source will not output the protected video content or may down- grade it to 1080p; even if downstream devices perform successful HDCP authentication at a lower level of HDCP protection, the results will not be consistent. If a down- stream device has no HDCP capability at all, there will likely be seen an error message or black or noise on the display. As an aid to troubleshooting, some professional video switchers respond to such noncompliant HDCP situations by outputting green screen video to the display to indicate that at least the display is active and receiving a signal. HDCP is backward compatible. For example, content protected by HDCP 1.4 will be displayed on an HDCP 2.2 display. If the content is not copy-protected, HDCP usually does not come into play. Figure 2 illustrates an example of how HDCP is handled under a common scenario. FIGURE 2: Results when copyrighted content is routed to HDCP compliant and non-HDCP compliant devices. PC with DVI output HDCP Display HDCP Display HDCP Display Non-HDCP Display Digital Matrix Switcher Matrix Input Matrix Output Not Authenticated Not Authenticated Authenticated Authenticated Authenticated Authenticated Not Authenticated Authenticated PC with DVI output 4K Blu-ray with HDMI 4K Blu-ray with HDMI • Switcher connects HDCP protected video content from Blu-ray to displays. • Authenticated HDCP displays show the content. • Non-HDCP display shows green screen generated by switcher, indicating that switcher output and display are active, but copyrighted content cannot be shown on this display. For the green screen, there are tools for troubleshooting HDCP noncompliance issues.