| 摘要 |
<p>PURPOSE:To prevent picture deterioration such as a spurious profile by selecting one noise, according to a quantization characteristic, from plural types of noises which have a period identical with the frame period of a picture signal and have different power and superimposing the selected noise on an input signal. CONSTITUTION:A noise generation circuit 1 generates a random noise signal which has a period identical with a frame pulse signal from a frame pulse input 10A and has a signal level which corresponds to an encoding parameter. For example, when there are B kinds of quantization characteristics which become rougher as they near a quantization No.8, the noise signal level is set to 0 for quantization characteristics No.1 to No.6 in the finer direction, and the noise signal level is set to (a) and (b) for quantization characteristics No.7 and No.8 in a rougher portion, respectively. When a rather fine quantization characteristic is selected, the noise signal level comes to 0 and a noise signal is not superimposed. However, when a rough quantization characteristic is selected, a noise signal with a level 4 (a) or (b) is superimposed on an output signal. Thus, random picture deterioration due to the spurious profile which is peculiar to rough quantization makes the picture deterioration inconspicuous.</p> |
