Under Serial Digital Interface(SDI), there are several standards adopted by the ITU-R and the Society of Motion Picture and Television Engineers( SMPTE) for a serial interface for the transmission of uncompressed digital video over coaxial cable. The SDI standard, standardized by the ITU-R under BT.656, specifies several transmission rates for composite video and component video in normal and high resolution in normal and wide screen format. Different SDI interfaces are defined for this purpose: SD-SDI for SDTV and EDTV, and HD-SDI for HDTV.
HD-SDI is suitable for high-definition television (HDTV) as defined in BT.709. The serial video stream has a data rate of 1.485 Gbit/s.
DC-SDI stands for D-Cinema Serial Digital Interface. This interface is designed for uncompressed HDTV signals without color subsampling (4:4:4) and a digitization of 12 bits. The resulting data rate is 2.97 Gbit/s. SDI signals are transmitted via RG-59 cables with BNC connectors and an impedance of75 ohms. The level of the data stream is 800 mV, the bridgeable distance is 300 m for data rates up to 270 Mbit/s, and 100 m for higher data rates. The data is encoded in Non Return to Zero Inverted( NRZ-I).
The SDI standards are for professional studio equipment, they are used for uncompressed and unencrypted video, whose packetized data stream is specified according to BT.656. In addition to video data, audio data of up to four audio channels can be transmitted in the data stream. In addition to the SDI variants mentioned above, there is a version with a higher transmission speed, the Quadrospeed Serial Digital Interface (QSDI), the Serial Digital Data Interface( SDDI) for data-reduced video signals for Betacam machines, and Compressed Serial Digital Interface (CSDI) for DVCpro.
12G-SDI is a 12 Gbps interface, specifically for UHD-1 signals with a data rate of 11.88 Gbps. This data rate transmits UHD signals with 2,160 vertical pixels and 50 frame changes with 10-bit quantization and 4:2:2 color subsampling.