Extracted from Wikipedia under term: Serial digital interface.
Serial digital interface (SDI) is a family of video interfaces standardized by "SMPTE" (Society of Motion Picture and Television Engineers). 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. 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.