VORRICHTUNG ZUR STEUERUNG DES QUANTISIERERS EINES HYBRID-KODIERERS

摘要

An apparatus is described for controlling the quantiser (404) of a hybrid coder (4). The hybrid coder (4) codes and quantises the frames of a video signal (A1) data block by data block. The quantiser (404) is controlled in dependence on the loading of a buffer memory. To increase the bit rate reduction in a standardised hybrid coder without loss of image quality, means (1, b1, 3) are provided by way of which the normal control of the quantiser (404) is replaced in special cases by another one. Such a special case exists when a data block is found to belong to the background of a scene for the first time. This data block is then transmitted with very high accuracy (very fine quantisation) whilst the data blocks of the subsequent video frames belonging to the same background are not transmitted at all (coarsest quantisation). <IMAGE>