HDCP
High-bandwidth Digital Content Protection (HDCP) is a form of digital copy protection to prevent the copying of digital audio and video content as it travels across connections (mainly DVI and HDMI).
The specification is proprietary, and implementing HDCP requires a license. One of the key terms of HDCP states that high-definition digital video sources must not transmit protected content to non-HDCP-compliant receivers. This sometimes causes handshaking problems, especially with older high-definition displays.