SDV unscrambled

The component serial digital interface (SDI) is already accepted as the standard for professional uncompressed video interconnection in the broadcast environment. Its ability to be used as a `drop in´ upgrade for a conventionally wired analogue composite system is extremely attractive. There are, however, issues associated with passing a 270 Mbit/s digital signal through wiring used to transporting a nominal 6 MHz bandwidth analogue signal. These include impedance discontinuity at patches/switches, cable loss/frequency response and proper terminations. The serial digital interface is achieved by taking the data in its `raw´ 10 bit parallel form at 27 MHz (Rec. 601 sampling) and serialising it. As part ofthe serialisation, the data is subject to scrambling to remove the DC content of the signal and ensure a good number of clock transitions occur in the stream to aid clock recovery at the receiver. The serial digital interface can usefully carry signals up to 200 metres without regeneration. For wider area interconnection, optical transmission is the obvious choice