Using the 8 bit CCIR Recommendation 601 digital interface

Describes an error feedback rounding technique which prevents contours being introduced by digital video processing equipment. It is also useful in 8-bit digital signal generators where it may be beneficial to use more than 8 bits within the generation processes and then apply error feedback rounding at the output. In addition to the applications discussed above, error feedback techniques can be useful for concealing quantising errors in reduced bit-rate signals. The theoretical basis for error feedback as it applies both to video signal processing and to bit-rate reduction coding is described. Despite the beneficial effects of error feedback, it is often necessary to preserve more than 8 bits as far as possible within equipment and to minimise the number of times a signal is rounded. The digital circuit interconnections both within and between items of studio equipment and the need to employ 8-bit CCIR Rec 601 interfaces are also described