TABLE OF CONTENTS Digital audio and video systems make it possible for the user to maintain a high and consistent sound or picture quality from beginning to end of a production. Unlike analog systems, the quality of the signal in a digital system need not be affected by the normal processes of recording, transmission or transferral over interconnects, but this is only true provided that the signal remains in the digital domain throughout the signal chain. Converting the signal to and from the analog domain at any point has the effect of introducing additional noise and distortion, which will appear as audible or visual artefacts in the programme material. Herein lies the reason for adopting digital interfaces when transferring signals between digital devices it is the means of ensuring that the signal is carried 'transparently', without the need to introduce a stage of analog conversion. It enables the receiving device to make a 'cloned' copy of the original data, which may be identical numerically and temporally.
The digital interface between two or more devices in an audio or video system is the point at which data is transferred. Digital interconnects allow programme data to be exchanged, and they may also provide a certain capacity for additional information such as 'housekeeping data' (to inform a receiver of the characteristics of the programme signal, for example), text data, subcode data replayed from a tape or disk, user data, communications channels...
