METHOD AND DEVICE FOR DECODING MOVING PICTURE

摘要

PURPOSE:To suppress deterioration in picture quality at an area in which a picture change is large by deciding a timing to revise a quantization step size from a block difference between frames and deciding a succeeding frame quantization step size correction value based on the inter-frame difference. CONSTITUTION:An inter-frame difference calculation circuit 108 calculates an inter-frame block difference SB and an inter-frame difference SF. Then a quantization step size revision timing decision circuit 109 decides the timing to revise the quantization step size so as to revise the quantization step size when the block difference SB is larger than a predetermined threshold level TH or smaller than a threshold level TL. Moreover, a quantization step size correction value decision circuit 110 calculates a correction value QS of the quantization step size from the inter-frame difference SF so as to increase the quantization step size when the inter-frame difference SF is large. Thus, the deterioration in the picture quality of a portrait in which a large picture change takes place is suppressed.