Picture Coding

A survey of recent German research in the field of picture coding is presented. The described coding methods are mainly based on extended differential pulse-code modulation (DPCM) techniques. A unified model of a feedback switched quantizer for picture coding is explained. Theoretical results show a 9-dB gain in SNR over that of DPCM. A simple realization is shown. For encoding the 1-MHz videotelephone signals, a two-stage coding system consisting of a two-dimensional DPCM in the first stage and a dot interlaced frame repeating codec in the second stage is described. A DPCM combined with a relevancy detector and runlength coder is used for coding the 5-MHz video signals of a high-resolution videotelephone. A special scanning technique assures compatibility with ordinary videotelephones. Good picture quality is obtained by coding the luminance and chrominance signals of color TV separately with DPCM and switched quantization into a 34 Mbit/s signal.