HIGH EFFICIENCY CODING DEVICE FOR DIGITAL VIDEO SIGNAL

摘要

PURPOSE:To prevent a quantization error from being concentrated on difference data whose transmission is omitted in order to provide compatibility of the high efficiency coding system between two video signal systems with different resolution or to reduce the transmission data quantity. CONSTITUTION:By taking a ratio N ( 4) of resolution of a high vision signal and an NTSC signal into account, sub blocks of (2X2=4) are formed. A block processing and average value generating circuit 2 generates a mean value (y) of each sub block. A men value coding circuit 8 encodes a mean value of (4X4) sub blocks. With respect to data of each picture element, a subtractor 7 generates a difference DELTAx with a mean value and the difference is coded by a difference coding circuit 9. A difference optimizing circuit 10 is provided after the circuit 9 and the coded difference value is changed in a quantization step width so as to minimize the sum of quantization errors with respect to four picture elements.