| 摘要 |
PURPOSE:To improve the coding efficiency in matching with a human eyesight characteristic. CONSTITUTION:A DCT transformation circuit 32 applies orthogonal transformation to original picture data 30 to provide an output of AC component 32a and DC component 32b. A picture characteristic discrimination circuit 36 calculates the distribution state of a high frequency significant coefficient of picture data from the AC component 32a to discriminate definition. The circuit 36 discriminates a local luminance level of the picture based on the DC component 32b and changes discrimination of high definition picture of the AC component 32a into discrimination of a low frequency picture in the case of low luminance. A quantization control circuit 38 sets a proper quantization width to a quantization device 34 in response to the discrimination result 36a. The quantization device 34 quantizes the AC component 32a and a delay circuit 40 adjusts a time of the DC component 32b. A variable length coding circuit 42 applies variable length coding to an output of the quantizer 34 and the delay circuit 40. |
