| 摘要 |
PURPOSE:To improve the reproduction picture quality not only to a general image in which the power Is collected to a low area coefficient but also to the image in which the power is collected to a high area by performing the adaptive coefficient selection to the coefficient distribution different for each picture element block. CONSTITUTION:By a blocking device 101, a rectangular area in an image is segmented as a picture element block from a digital image signal, an orthogonal transformation is performed by a transformation part 103 and the transformation coefficients are obtained. An activity calculator 200 calculates the variance of the image in a block. From the obtained variance, a power conservation ratio deciding device 202 decides the power to be conserved at the time of coding. Based on the transformation coefficients from the transformation unit 103 and the power conservation ratio from the power conservation ratio deciding device 202, an optimum mask is selected by a mask deciding device 204. By the mask, the transformation coefficients are selected in a coefficient selector 105. The transformation coefficients after selection are quantized by a quantizing device 107, coded by an encoder 109 and subsequently, outputted to a transmission line 111. |
