The present paper deals with some questions concerning digital coding of TV signals for ISDN-B applications, without emphasis being placed on the source encoding techniques; the main objective of this paper is not only to indicate the implications caused by the transmission of different TV signals-components according to CCIR Recommendation 601, MAC, and HDTV-but also to investigate the marginal conditions created by digital transmission. Digitization of the signal components, the problems of filtering resulting therefrom, sampling rate conversion, and the new system family MAC as well as aspects of HDTV transmission and coding are described. In the second main part, appropriate substandards are derived from the digital studio standard for digital transmission, using data rates standardized by the CCITT. A description is given of some coder concepts, and finally some important aspects of broad-band techniques are dealt with.

The data rate of the third level of the digital hierarchy is regarded as particularly economical for the international exchange of television programs via satellite. Nonetheless, the exchange is aggravated by the fact that this level has not been standardized on a world-wide scale. For example, a rate of 32 Mbits/s is used in Japan, 34 Mbits/s in Europe, and 44 Mbits/s in North America. The present paper details a procedure which allows digital TV signals of studio standard to be transmitted on 32-, 34-, or 44-Mbit/s channels by means of sampling rate conversion and adaptive source coding. For the case where an international link consists of sections using different data rates, a transcoding method is described and tested in computer simulations which converts the third-level rates into each other, without cascading of DPCM-decoders and-encoders.

Digital comb filter devices with one or two line memories or with picture memories for the demodulation of PAL color TV signals are presented and compared with respect to their effects on subjective picture quality. The color video signals are assumed to be sampled at four times the color subcarrier frequency, the sampling frequency adopting a definite phase with respect to the color subcarrier. Methods are discussed which are able to stabilize the frame by frame changing of the sampling patterns in the case of comb-filter devices containing only one line memory. It is shown that comb-filters with two line memories and with picture memories have inherent stability and that the decoder with a frame delay guarantees at the expense of a sophisticated hardware full resolution in non-changing parts of a picture sequence.

A quantizing method for chrominance signals is presented which takes into account that the visibility of small color differences and the areas of reproducible colors are a function of luminance. For the evaluation of quantizing characteristics and for an estimate of the effectiveness of such a procedure, CIE (Commission International de l'Eclairage) formulas are used. It is proposed to subdivide the color space into several layers of constant luminance signal and to choose, switched by the luminance signal, an individual quantizer for each layer. Such quantizers are calculated for two different coding schemes: quantizing the TV chrominance signalsU_{R-Y}andU_{B-Y}directly or quantizing chrominance signals which have been transformed into a color space derived from a neurophysiological model of vision. Because of practical reasons the quantization ofU_{R-Y}andU_{B-Y}is preferred and elaborated in more detail. The calculated non-linear quantizing grids are approximated by two different methods, with small rectangular elements, or they are piecewise linear approximated by interpolation. To achieve a color difference of\DeltaE_{1964 CIE} = 4.4as maximum distortion, a PCM quantization of 5 bits inU_{R-Y}andU_{B-Y}is required. First order entropies indicate an average bit rate of 3.5 forU_{R-Y}and 2.7 forU_{B-Y}.