Decrease manner of the mosquito noise which it occurs when decoding the graphics data and decoding device null of the

摘要

PURPOSE: To obtain a decoder which is capable of excellently reducing the mosquito noise generated at the time of decoding image data and performing a contour compensation. CONSTITUTION: A first activity detection part 7 where the decoding image data read from an image memory 16 is supplied supplies the first activity value detected for the range of the first size designated in a decoding image to a control signal generation part 6. A second activity detection part 8 supplies the second activity value detected for the range of the second size which is smaller than the first range to the signal generation part 6. The signal generation part 6 generates a control signal to be used as a coefficient in the multiplier in a frequency characteristic change part 9 based on the first and second activity values and a block quantization width value. The change part 9 attenuates high frequency components for an image part where the block quantization width value is large and the image part where the activity value is small, and intensifies the high frequency components for the image part where the block quantization width value is small and an edge part where the activity value is large.