HDMI

High Defenition Multimedia Interface (HDMI) is a digital video and audo interface capable of transmitting uncompressed streams. It provides a universal standard connector that is used in PCs, DVD players and televisions. It supports all standards of TV and PC video format including standard, enhanced and high defenition. HDMI can also support 8-channel uncompressed digital audio at 192 kHz sample rate with 24 bits/sample as well as compressed audio formats such as Dolby Digital of DTS. HDMI is also the replacement for older technologies such as VGA and DVI. In almost all cases, HDMI is accompanied by the DRM (Digital Rights Management) technology, HDCP.

HDCP

High Definition Content Protection is a form of DRM (Digital Rights Management) created by Intel to control video and audio data as it travels across HDMI and DVI connections. Its main task is to make sure unencrypted data isn't transmitted. It acheives this by using the following methods:

• Not allowing HD content to be used on non licensed devices.
  
• The encryption of data sent over the HDMI or DVI interface. This prevents eavesdropping.
• Blocking devices designed to transmit or receive un-encrypted HD data.
  

To use HDCP you have to have HDCP devices, both the client and serving device. This also includes the OS if the HDCP signal is being sent from a PC. If your setup doesn't have HDCP and you are trying to access high definition content, then you'll only see DVD quality broadcasts.

Both of these technologies are prevailant in the HD-DVD and Blue-Ray scene, as well as with HDTVs. However, recently the new ATI HD 2xxx series of cards have been making headlines because every one of the graphics cards in this range encorporates both HDMI and HDCP.