| 摘要 |
PURPOSE:To attain detail control relating to the property of an input picture by providing a circuit deciding an upper limit and a lower limit of a quantization step width in response to a prediction error of a picture signal having an input picture or a mean value of plural prediction errors to the coder so as to control the quantization step width. CONSTITUTION:The coder is provided with a circuit 101, which uses a prediction error of a picture element or a mean value of plural prediction errors so as to decide an upper limit and a lower limit of a quantization step width. For example, a quantization step width limit circuit 101 decides an upper limit of the quantization step width with respect to the quantization step width outputted through a quantization step width control circuit 330. The upper limit is decided in response to a prediction error inputted to the quantization step width limit circuit 101 from a subtractor 304 through a line 305. Thus, detailed control of the quantization step width corresponding to the property of the input picture is attained. |
