Serial Digital Interface

Serial digital interface (SDI) is a family of video interfaces standardized by SMPTE (The Society of Motion Picture and Television Engineers). For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video.
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.

An emerging interface, commonly known in the industry as dual link HD-SDI and consisting essentially of a pair of SMPTE 292M links, is standardized in SMPTE 372M; 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. A more recent interface, 3G-SDI, consisting of a single 2.970 Gbit/s serial link, is standardized in SMPTE 424M that will replace the dual link HD-SDI.

These standards are used for transmission of uncompressed, unencrypted digital video signals (optionally including embedded Audio and/or Time Code) within television facilities; they can also be used for packetized data. Coaxial variants of the specification range in length but are typically less than 300 meters. Fiber optic variants of the specification such as 297M allow for long-distance transmission limited only by maximum fiber length and/or repeaters. SDI and HD-SDI are currently only available in professional video equipment; various licensing agreements, restricting the use of unencrypted digital interfaces to professional equipment, prohibit their use in consumer equipment. 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.