| 摘要 |
PURPOSE:To prevent visual deterioration in a picture quality of a decoded picture by applying quantization so that a decoded picture signal has a quantity change closest to a spatial change quantity of an original picture data. CONSTITUTION:A difference between a true value x1 of a noted picture element and a true value x0 of a surrounding picture element such as a preceding picture element (change in horizontal direction) DELTAr(=x1-x0) is detected. A decoding level X0 of the picture element x0 is generated by a local decoder 52 and 4 decoding representative levels (I0+MIN, I1+MIN, I2+MIN, I3+MIN) are generated by local decoders 48-51. Then subtraction circuits 40-43 calculate a difference between the decoding representative levels and the decoding level X0 (predicted change) DELTA0, DELTA1, DELTA2, DELTA3 are calculated. Moreover, a change quantity closest to a change DELTAr of the original picture data is detected among the 4 differences and a quantization code in response to the detection is selected by a code selection circuit 39. Thus, the deterioration distinct visually is prevented. |
