Composite is the lowest common denominator of video signals. A composite signal runs all color and brightness information on a single cable, resulting in lower-quality video compared to the quality of other formats. Nearly all video devices have a composite input and output. This format uses a single RCA or BNC connector.
In professional editing environments, composite video signals are most commonly used for troubleshooting, for menu outputs, and for low-quality preview monitoring. For consumer and home use, composite signals are often used to connect VCRs or DVD players to televisions.
Serial Digital Interface (SDI) is the standard for high-end, uncompressed digital video formats such as D1, D5, and Digital Betacam. If you want to capture digital video from these formats at the highest possible quality, you need a video interface with an SDI input and output, as well as a high-performance disk array (a set of disk drives grouped together to read and write in parallel), to accommodate the high data rates you’ll work with. Many devices can send both video and audio data through a single SDI connection.
High Definition Serial Digital Interface (HD-SDI) is a higher-bandwidth version of SDI designed for the extremely high data rates required by uncompressed HD video. Like SDI, HD-SDI is capable of sending both video and audio through a single connection. The following decks have HD-SDI interfaces: DVCPRO HD, D-5 HD, and HDCAM decks.
Some devices provide even higher data rates by pairing two HD-SDI channels together (known as dual-link HD-SDI). Uncompressed HD RGB video and other digital cinema formats can be transmitted using dual-link HD-SDI.
Serial Digital Transport Interface (SDTI) is based on SDI, allowing native video formats to be sent in real time within an SDI video stream. SDTI does not define a specific video signal format but instead uses the structure of SDI to carry any kind of data. This allows video facilities to use their existing SDI patchbays and routers to transfer other native video formats, or transfer any kind of data. For example, some DV decks can transfer DV via SDTI, which means native DV can be transferred long distances over existing coaxial cable instead of the usual FireWire connection. Other formats, such as HDCAM and MPEG, can also be transferred via packets within an SDTI transport stream.
S-Video, also known as Y/C, is a higher-quality video signal used by high-end consumer video equipment. The image looks sharper and has better color than a composite video image because S-Video keeps the color and brightness information separate on two cables. Most low-cost analog-to-digital video interfaces have S-Video as their highest-quality video connector. Use care when working with S-video connectors; the four delicate pins can be bent easily.
Component YUV and Component RGB
Professional video equipment, such as Betacam SP decks, has component YUV (Y′CBCR) video inputs and outputs. Component YUV separates color and brightness information into three signals, which keeps the color quality more accurate than that of other systems. Component YUV is as good as analog video gets. High-end consumer devices, such as DVD players and televisions, have increasingly begun to support component YUV.
Note: Another form of component video, component RGB, is not as widespread on professional equipment as component YUV.
Both component YUV and RGB signals use from three to five connectors. You can use three BNC connectors, plus a fourth (typically labeled “genlock” or “house sync”) to send a timing signal. Sync can also be embedded in the Y or G part of the signal (using three connectors), a separate composite signal on a fourth connector, or separate H and V drive signals (using five connectors). See your equipment’s documentation for more information.
High-Definition Multimedia Interface (HDMI) supports both digital television and computer signals and can also include multiple digital audio channels. HDMI devices are compatible with single-link digital DVD signals via an adapter, although no audio or additional metadata can be included. Many HD display devices and digital television set-top boxes include HDMI connectors.
FireWire 400, also called IEEE 1394a or i.LINK, is the consumer and professional standard for formats such as DV, DVCAM, DVCPRO, DVCPRO 50, DVCPRO HD, and HDV. FireWire is an inexpensive and easy way to capture and output high-quality digital video using a variety of camcorders and decks and is capable of data rates as high as 400 Mbps. Standard FireWire cables can be up to 4.5 meters long.
There are two kinds of FireWire connectors: a 4-pin connector (typically found on video equipment such as camcorders or decks) and a 6-pin connector (used for computer equipment). However, some newer video equipment uses the 6-pin connector, and some video interfaces use the 4-pin connector. See your equipment’s documentation for more information.
FireWire 800, also called IEEE 1394b, is the next generation of FireWire after IEEE 1394a, a higher-bandwidth version capable of data transfer speeds of up to 800 Mbps.
FireWire 800 is also capable of supporting cable distances of up to 100 meters.
In addition to the standard 9-pin-to-9-pin FireWire 800 cables, 9-pin-to-4-pin and 9-pin-to-6-pin FireWire 400 to FireWire 800 cables are also available to connect older devices to a FireWire 800 interface.
Note: FireWire 800 is commonly used to connect hard disks and other data peripherals to your computer, but this connector is rarely used to connect video devices.
Consumer PAL equipment sometimes has a special connector called a SCART connector. A SCART connector has multiple pins that run composite, component RGB, and stereo audio in one bundle. SCART input or output can be broken up into individual connections using special adapters available from video and home electronics stores.