JPS5721172A - Adaptive quantization circuit - Google Patents

Abstract

PURPOSE:To express a changing part in less number of bits and to compensate the level variance of an input video signal automatically, by picking up the luminance level in the range where a digital video signal is transited from shade to light through the use of a renewed reference level, from the 2nd quantization circuit. CONSTITUTION:The luminance level of a video signal from a sensor 21 is quantized at the 1st quantization circuit 22, and the number of video elements every quantized luminance level is counted every block as the representative value of white and black at an integration count circuit 23. The content of the circuit 23 is read out, it is read out at a central value detection circuit 25 with an address counter 24, the central value of the white and black representative value is determined, and the reference level set to a reference level set circuit 26 is compared with the central value. According to the renewed reference level at the 2nd quantization circuit 27, the level change when the quantized digital video signal moves from shade to light from the circuit 22 is compensated automatically.