The serial digital data interface (SDDI) is designed to assist studio equipment with the transmission of multiple compressed signals on a single 270 Mbps coaxial SDI cable. Unlike most networking protocols, SDDI offers a synchronous protocol which makes its introduction into the broadcast studio relatively simple. The primary aim of SDDI is to facilitate transmission of compressed video data between equipment without the need to decode back to full bandwidth ITU-R 601. Furthermore, additional attractive features such as 'faster-than-real-time' data transfers can be achieved on a single SDDI link. The protocol of the SDDI has been proposed to both the EBU and SMPTE as a potential future standard. The development of SDDI is as yet at an early stage compared to other computer networks. Furthermore, it is not as broad in application as general purpose networks since it does not implement hand-shaking protocols. Nevertheless, there are advantages in using a synchronous video network in areas where signal timing is critical. In this area, general purpose computer or telecom networks cannot, as yet, guarantee the performance required. The paper describes the details of the SDDI protocol which offers a wide bandwidth with facilities for auto-routing in a network configuration. The paper also emphasises the backwards compatibility issue which is important for those who might plan to install SDDI equipment into a video/SDI infrastructure.
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