PICTURE CODER AND PICTURE DECODER

摘要

PURPOSE:To improve a coding efficiency and one-frame processing speed by adding a function comparing a current frame with a 2-preceding frame to the coder and decoder and sending only a code representing invalidity for a part discriminated when the both are equal. CONSTITUTION:A discriminator 5 discriminates a picture data from a frame memory and outputs a result representing whether the data is valid or invalid. A coder 10 applies orthogonal transformation to a block discriminated to be valid in a picture and applies quantization thereto and sends the result while allocating a code. Moreover, the coder 10 applies only code allocation of an invalid block to the block discriminated to be invalid and sends the result. Since a discrimination device 5 discriminates a valid/invalid part through the comparison with a representative value of a preceding frame, even a changing picture in an actual picture may be discriminated to be an invalid part. Then a valid frame per several frames is produced without fail in each frame of a picture data in a frame memory so that mis-discrimination is not caused for several consecutive frames.