HDCP (High-Bandwidth Digital Content Protection) is a form of DRM which was originally developed by Intel to protect digital content it is transmitted through DVI and HDMI connections.
HDCP devices are required to downgrade high-definition video feeds to DVD quality if output devices do not support HDCP. In this way high-definition content is protected from piracy, but is still allowed to play, just at a lower quality.
Many new computer monitors and video cards are HDCP compliant. Most HD DVD and Blu-ray devices will only output high-resolution video using HDCP.
Microsoft Windows Vista supports HDCP.