| 摘要 |
PURPOSE:To perform the effective quantization in real time, by updating the reference level based on the luminance level distribution in a readout luminance level histogram and carrying out the quantization with the updated reference level. CONSTITUTION:The analog picture signal given from a sensor 21 is converted into a digital picture signal through a quantizing circuit 22. The counting value of a luminance level histogram which is counted by a luminance level histogram circuit 23 and read out by an address counter 24 is decided whether its minimum value shows a black level by a center value detecting circuit 25 and from the highest frequency value, the maximum value and the minimum value respectively of the luminance level distribution. At the same time, the center value is detected. This detected center value is compared with the reference level of the preceding block at a level setting circuit 26 to update the reference level. Based on the updated reference level, a quantizing circuit 27 converts the 64-value digital picture signal into the 16-value digital picture signal to deliver it to a terminal 28. |
