Connection Types

Who would have thought wiring could get so complicated? Here's the skinny (and the not so skinny) on the various cables and connections commonly found on HDTVs and other high-def audiovisual gear.

Digital Connections are increasingly being used to maximize signal integrity and establish secure, "smart" links between devices.

HDMI HDMI (High Definition Multipurpose Interface) is the standard in digital HD connectivity, a combined audio/video cable that makes a whole tangle of older wires obsolete. It's a nineteen-pin connection that sends both digital video and multi-channel audio through a single line, while simultaneously managing control functions such as HDCP copy protection. Created by Intel and based on powerful encryption algorithms, HDCP is the rising star in digital rights management (DRM) technology, and fully integrated into HDMI. Other advanced functions include the ability for devices to recognize each other's capabilities, and optimize signals based on the results. HDMI features a miniature connector, resembling a USB plug.

DVI DVI (Digital Video Interface) was originally developed for the computer industry, and then transplanted to HDTV. It is uses a hefty 29-pin connector, usually with some of the pins removed. It is rapidly being replaced by HDMI, but can usually communicate with HDMI via an adaptor. Like HDMI, it relies on the HDCP copy protection scheme. DVI-D is the version most commonly seen on HDTVs and set-top boxes - the plug may be missing five or more pins. DVI-I is typically found only on front-projection HDTV monitors, and has all 29 of its pins in place.

FireWire (IEEE1394, I-Link) was originally developed by Apple Computers to connect PCs with digital cameras, camcorders, and other external devices. Like HDMI, it is a high-speed connection that can carry digital video, audio, and control functions in a single cable. But unlike HDMI, it does not rely on HDCP but instead uses a different copy-protection scheme, called DTCP or 5C. And therein lays the key issue for FireWire's long-term future in the living room: DTCP is an open standard, which tends to make the entertainment industry nervous about its vulnerability to hackers.

TOSlink TOSlink (also known as EIAJ) is a fiber-optical connection used for transmitting digital audio signals. The technology has been around for decades, but recent improvements in fiber-optic manufacturing have made this a very popular audio connection for high-end home entertainment gear.

Analog Connections do not support advanced functions like digital rights management, and as such are losing their prominence in home entertainment. When confronted with a copy-protected signal, an analog connection may drop off entirely, or at best display a low-resolution version of the protected program. However, they are still found on audiovisual gear, and serve as a useful "common denominator" connection in cases where a device does not support a digital connection.

Component video is a triple-plug RCA-style connector that can reliably transmit a high-definition video signal in analog form. If you need to hook up to device that doesn't support a digital connection, this is your cable of choice. The analog data, known as a raster signal, may be split into the traditional red, green, and blue (R/G/B) or by using the alternative "wideband" scheme (Y/Pr/Pb). Neither mode is inherently better than the other, but both devices must support the same scheme. The component video jacks on the back of the device will usually be labeled one way or the other, with Y/PR/Pb being the more common format on HD devices.

RGB+H/V RGB+H/V is an older analog video connection, usually found only on front-projection monitors. It uses five separate cables to convey color and synch data.

VGA VGA is the familiar 15-pin, d-shaped, analog video connector that's on the back of most computer monitors. It uses five wires, usually bundled into a single cable, to send color and synch information to the display.

S-video S-video is an older, two-wire connection that was designed for the older NTSC standard. It cannot handle HD video or progressive-scan signals.

Composite Video is the grandfather of them all, a one-wire connection that is now obsolete.

A/V receivers

If you have any aspirations at all to being a home theater nut, you probably already own an audiovisual (A/V) receiver. But since a large part of its job is to serve as a "wiring hub" for all your other gear, it's crucial that this device has the right input and output connections. If it doesn't have HDMI or DVI capability, it may be time for an upgrade. Newer models not only have multiple HDMI ports, but can handle source-switching between high-def inputs, so you'll be able to easily surf between the cable tuner and other digital signal sources.

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