Kodierung eines Bildsignals mit Berücksichtigung des Kontrasts in jedem Bild und Dekodierung analog zur Kodierung

摘要

On encoding an original picture signal comprising signal portions representative of original pictures, respectively, a contrast detecting unit (41) detects a measure of contrast in each picture in response to signal blocks representative of block areas, respectively, which have a common size in the picture in the manner known in transform encoding. Such measures are variable in a predetermined number of stages. With reference to the stages, a picture encoding parameter determiner (72) determines picture encoding parameters. Supplied with the encoding parameters, a picture encoder (71) encodes the original picture signal into an encoded picture signal. Inasmuch as the measures are detected in consideration of the signal blocks, the encoding is carried out on the signal blocks in effect. The contrast detecting unit, as herein called, preferably divides the pictures into a background region and a picture or non-background region so that the encoding parameters are determined with additional reference to the regions. The measures may be detected either among the block areas of each picture or among picture elements of each block area. More preferably, a complexity detecting unit is used in addition to the contrast detecting unit. The picture encoder is typically either a transform encoder or a predictive encoder.