The interface is self-synchronizing and self-clocking. Data is encoded in NRZI format, and a linear feedback shift register is used to scramble the data to reduce the likelihood that long strings of zeroes or ones will be present on the interface. Uncompressed digital component signals are transmitted. The HD bitrates have a shorter maximum run length, typically 100 meters (330 ft). Using equalization at the receiver, it is possible to send 270 Mbit/s SDI over 300 meters (980 ft) without use of repeaters, but shorter lengths are preferred. The specified signal amplitude at the source is 800 mV (☑0%) peak-to-peak far lower voltages may be measured at the receiver owing to attenuation. This is the same type of cable used in analog video setups, which potentially makes for easier upgrades (though higher quality cables may be necessary for long runs at the higher bitrates). The various serial digital interface standards all use (one or more) coaxial cables with BNC connectors, with a nominal impedance of 75 ohms. There are various mod kits for existing DVD players and other devices, which allow a user to add a serial digital interface to these devices. Several professional video and HD-video capable DSLR cameras and all uncompressed video capable consumer cameras use the HDMI interface, often called clean HDMI. SDI and HD-SDI are usually available only in professional video equipment because various licensing agreements restrict the use of unencrypted digital interfaces, such as SDI, prohibiting their use in consumer equipment. Fiber optic variants of the specification such as 297M allow for long-distance transmission limited only by maximum fiber length or repeaters. Coaxial variants of the specification range in length but are typically less than 300 meters (980 ft). SDI is used to connect together different pieces of equipment such as recorders, monitors, PCs and vision mixers. These standards are used for transmission of uncompressed, unencrypted digital video signals (optionally including embedded audio and time code) within television facilities they can also be used for packetized data. 6G-SDI and 12G-SDI standards were published on March 19, 2015. 3G-SDI (standardized in SMPTE 424M) consists of a single 2.970 Gbit/s serial link that allows replacing dual link HD-SDI. Dual link HD-SDI consists of a pair of SMPTE 292M links, standardized by SMPTE 372M in 1998 this provides a nominal 2.970 Gbit/s interface used in applications (such as digital cinema or HDTV 1080P) that require greater fidelity and resolution than standard HDTV can provide. Īdditional SDI standards have been introduced to support increasing video resolutions (HD, UHD and beyond), frame rates, stereoscopic (3D) video, and color depth. A related standard, known as high-definition serial digital interface (HD-SDI), is standardized in SMPTE 292M this provides a nominal data rate of 1.485 Gbit/s. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video. Serial digital interface ( SDI) is a family of digital video interfaces first standardized by SMPTE (The Society of Motion Picture and Television Engineers) in 1989. SMPTE (The Society of Motion Picture and Television Engineers) Serial digital interface uses BNC connectors
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