| 摘要 |
PURPOSE:To reduce distortion due to sudden variation in the light-shade level of a reproduced image by lowering a threshold value for deciding an insignificant coefficient or significant coefficient more and more as there are more and more insignificant blocks at the periphery of a block to be encoded. CONSTITUTION:The threshold value T is adjusted by using a storage part 17 and a threshold value setting part 18. Namely, it is decided whether a block which is already encoded and positioned nearby the block to be encoded is the significant block containing significant coefficients or insignificant block consisting of only insignificant coefficients, and the threshold value T is set smaller and smaller as there are more and more insignificant blocks nearby the block to be encoded. Thus, the frequency of the generation of insignificant blocks consisting of only insignificant coefficients is reduced. Consequently, distortion due to sudden variation in the light-shade level of the reproduced image is reduced. |
