First-generation HDTV displays used analog component video (Y Pb Pr) connections to display high-definition (i.e. 1080i or 720p) content. While component video produced a stunning improvement in picture quality over standard definition S-Video or composite video connections, it remained vulnerable to piracy and poor cable quality. Because the content isn't encrypted, any competent hacker could capture the component video signal and save a high-resolution copy for illegal redistribution purposes. Furthermore, since it's an analog connection, cheap cables could impact picture quality.
Surprisingly, both of these concerns are largely theoretical. HD content is too massive for pirates to burn onto a DVD or transport over today's broadband connections (it could take days to upload a full-length 20Mbps movie). In addition, since HDTV sets remain relatively expensive, most people aren't going to try to save a few cents on cheaper component video cables, so the cable quality issue is moot.
Regardless of the validity of these concerns, studios and consumer electronics companies were anxious for a digital alternative to component video. Fortunately for them, during this same timeframe, the computer industry was in the midst of transitioning from analog VGA connectors to the Digital Visual Interface (DVI). Since DVI can transmit up to 5Gbps of uncompressed video content (far in excess of HD transmission rates), it is an ideal solution for newer display technologies like plasma or LCD since it enables manufacturers to create an all-digital display solution.
Another benefit of DVI is its use of the Extended Display Identification Data (EDID) standard. EDID lets other devices ask the display about what resolutions and scan rates it supports and also its native, or preferred, resolution. This allows users to insert (or hot-plug) a display into any DVI device and automatically select the optimal video resolution.
HDCP: An Irresistible Force
Although DVI was designed as a computer-centric solution, display manufacturers adopted it en masse. Given its digital nature, cable quality concerns were virtually negated. In addition, EDID also reduces complexity. Before DVI/EDID, users had to know or guess if their display supported 480p, 720p, or 1080i resolutions. If they guessed wrong, the monitor could go berserk and display video noise. The resultant mess was likely to generate support calls as novice users struggled to undo the damage. By contrast, with a DVI display, the device generating the HD signal knows beforehand what resolutions the display supports so it should be considerably harder to select an invalid video-output resolution.
But the real benefits of DVI can only be seen on pure digital displays such as LCDs and some plasmas. An all-digital solution shows you video lines that typically can't be detected on a tube fed by a component connection. This occurs for two reasons. First, even on many flat-screen displays, the curve of the tube causes a few lines of video to be lost. Second, the analog-to-digital conversion required by component cables may cause small portions of the video data to be lost.