An RGB cable is used in transferring analogue video signals from a video source to a display. In a typical home theatre application, the RGB cable is referred to as component which uses different methods to transfer image information than other common RGB cable standard types. Common uses for the RGB cable include connecting DVD players, PC video cards and video cameras to a television, HDTV or computer monitor.
Standard RGB Cables
RGB uses three colours (red, blue and green) and blends them together with horizontal and vertical sync information to project a complete video image. RGB supports standard and HD resolutions up to 1080i. The source decodes video, separates signals and transfers the colours and sync information to the preferred display. How these signals are transferred is dependent on the RGB cable. There are several H/V sync transfer methods associated with specific RGB cable types. RGBS uses a single separate component wire for horizontal and vertical sync. RGsB combines horizontal and vertical sync with the green coloured wire. RGBHV transfers horizontal and vertical sync on two dedicated wires.
Analogue Component YPbPr
The most common type of RGB cabling found on consumer electronics is analogue component, or YPbPr. This form of cable uses a different method of colour and sync transfer than a standard RGB cable. Rather than using red, blue, green and H/V sync transfer, luma and chroma signals are employed. This helps save on limited cable bandwidth. The green or Y wire carries the luma data which controls achromatic (colourless) brightness. The Blue or Pb cable is used to carry the blue chroma signal while the red or Pr cable carries the red chroma. Component cabling allows for progressive scan images as well as interlaced. Component currently supports standard resolutions up to 1080i.
RGB cables typically use two forms of connectors--BNC and RCA. BNC connectors are used mainly on professional applications and are commonly found in TV stations, security networks, and other areas not common for consumer use. BNC uses a locking mechanism which secures the cable in place. RCA connectors are found on many consumer electronics and home theatre applications.
RGB, although it does support HD up to 1080i, is still an analogue application. Because of this, length, shielding and materials all have an effect on signal quality and strength. Better connectors, shorter lengths, better insulation and shielding will improve picture quality.
Component cabling has no high-bandwidth digital content protection (HDCP) support, which is a digital copy protection standard. HDCP is used in digital video cabling, particularly HD content over HDMI or DVI. Talks about 1080p over analogue were rejected by the Consumer Electronics Association (CEA), which limits the max resolution on component video.