IMAGE SIGNAL DECODING DEVICE AND IMAGE SIGNAL DECODING METHOD

摘要

PURPOSE: To eliminate block distortion without blunting an edge and a detail part by changing the pass band characteristics of an LPF applied to picture elements near a block boundary corresponding to a dynamic range and eliminating the block distortion caused at the time of decoding. CONSTITUTION: Highly efficiently encoded transmission image data S1 are passed through a frame decomposing circuit 2, decoded in a block decoding circuit 4 and supplied to a block delay circuit 5 and a dynamic range detection circuit 6. The circuit 6 obtains the dynamic range(DR) of respective blocks from a maximum value and a minimum value within the block and supplies it to a coefficient table circuit 10. The circuit 10 reads a coefficient set stored beforehand with the DR as address information and supplies it to a product-sum operation circuit 9. The circuit 9 performs a prescribed arithmetic operation by using the supplied coefficient set, applies the LPF of the pass band characteristics corresponding to the DR only to the picture elements near the block boundary and adaptively eliminates the block distortion.