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. 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.
Additional SDI standards have been introduced to support increasing video resolutions (HD, UHD and beyond), frame rates, stereoscopic (3D) video, and color depth. 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. 3G-SDI (standardized in SMPTE 424M) consists of a single 2.970 Gbit/s serial link that allows replacing dual link HD-SDI. 6G-SDI and 12G-SDI standards were published on March 19, 2015.