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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.〔(【引用サイトリンク】title=3Gb/s SDI for Transport of 1080p50/60, 3D, UHDTV1 / 4k and Beyond )〕 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. As of August 2014, 6G-SDI and 12G-SDI products are already in the market, although their corresponding standards are still in proposal phase. 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. 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 or repeaters. 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. Several professional video and HD-video capable DSLR cameras and all uncompressed video capable consumer cameras use the HDMI interface, often called Clean HDMI. 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. ==Electrical interface== The various serial digital interface standards all use (one or more) coaxial cables with BNC connectors, with a nominal impedance of 75 ohms. 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 specified signal amplitude at the source is 800 mV (±10%) peak-to-peak; far lower voltages may be measured at the receiver owing to attenuation. Using equalisation at the receiver, it is possible to send 270 Mbit/s SDI over 300 metres without use of repeaters, but shorter lengths are preferred. The HD bitrates have a shorter maximum run length, typically 100 meters. Uncompressed digital component signals are transmitted. 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. The interface is self-synchronizing and self-clocking. Framing is done by detection of a special synchronization pattern, which appears on the (unscrambled) serial digital signal to be a sequence of ten ones followed by twenty zeroes (twenty ones followed by forty zeroes in HD); this bit pattern is not legal anywhere else within the data payload. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「serial digital interface」の詳細全文を読む スポンサード リンク
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