Abstract: An image signal coding system encodes analog image signals into digital signals in a high-definition digital video tape recorder (D-VTR). A scrambling portion rearranges the image data of a frame formated in the order of vertical subsampling line into a predetermined unit of blocks to distribute the highly variable portions and substantially linear portions in the image data uniformly, while an activity calculation portion calculates a horizontal projection sum and a vertical projection sum of discrete coding transform factors in a unit block and a block activity, respectively to determine a coding area and a quantization step size.

Abstract: The image signal band compressing method employs a three-dimensional motion compensating technique, an intraframe and an interframe processes which are alternatively executed. The transfer rate of the intraframe to the interframe is set to 4:1 in a unit of fixed length. The intraframe process is defined such that the present frame image data is compressed in a variable length compressing manner by way of two-dimensional discrete coding transform. The interframe process is defined such that motion data is estimated by comparing the present frame and the preceding frame, the present frame is expected on the basis of the motion data and the difference data between the motion compensated image data and the present frame data.