BBC R&D

Abstract

The characteristics of Walsh-Hadamard transformation systems are examined with a view to reducing the data rate of digital television signals. Transformed signals have been measured using several different transformation arrangements by means of a Walsh spectrum analyser, in which television signals are correlated with Walsh functions.

It is found that a slightly higher data rate is required to describe the transform coefficients with linear coding than is needed for the original signal. However, a more efficient encoding of the transform could be provided using non-linear quantisation or adaptive bit-rate reduction systems. Two-dimensional transformation and the use of sampling frequencies which concentrate the energy of colour signals in the transform could improve the performance of these bit-rate reduction systems.