Compressor function for analogue HDTV component signals

Abstract

The optimum compressor function for analogue HDTV component signals was determined by ascertaining the threshold of noise perception depending on the picture brightness in the range between 2 and 330 cd/m 2. The result turned out to be very similar to a logarithmic function. A processor-controlled, digital predistortion unit and a complementary correction unit facilitated the realization of a logarithmic compressor function and a gamma law function having an exponent of 0.45. The measurement of the threshold of noise perception for distorted video signals gave further evidence for uniform visual distribution of transmission noise over the brightness range by the logarithmic compressor function. The gamma law is less suitable for this purpose. This result was also supported by a demonstration with a natural test picture. The results of these tests show that the Weber-Fechner law is valid for the perception of noise in nearly the whole range of brightness, which was under consideration.