Hybridprädiktionscodierer und -decodierer für digitale Videosignale

In a coder for digital video signals, the difference between the ditigal video signals and prediction signals is subject to a transform prior to quantisation. In particular, a transform applied to the values of a block of pixels to produce sets of coefficients in the spatial frequency domain. A quantiser (14) acts on the coefficients to product a coded output which is decoded at a local decoder (18) operative on the coded output. The coder further includes means (20) for adding the prediction signal to the output of the local decoder (18) and a framestore (22) which receives the output of the adding means (20). A multiplier (26) multiplies the output of the framestore (22) by a factor slightly less than unity to form the prediction signal.