Patent ID: 7920153

Claim:
A noise quantity measuring apparatus comprising: a memory circuit which stores therein a video input signal corresponding to at least one frame; a subtraction circuit which calculates differences in luminance level developed every pixel between video signals in plural arbitrary areas at a newly inputted video input signal and a video signal in the same area read from the memory circuit; an integration circuit which adds absolute values of the luminance level differences developed every pixel in the arbitrary areas, which have been calculated by the subtraction circuit, every said arbitrary area, and outputs sums of the luminance level differences every said plural arbitrary areas; a luminance determination circuit which compares the luminance levels of the respective pixels that constitute the video signals and a predetermined threshold value every said arbitrary areas, and outputs a detection signal to the corresponding area if even one of the luminance levels exceeds the threshold value; and a minimum value output circuit which outputs the minimum sum of luminance level differences exclusive of the area for the detection signal outputted from the luminance determination circuit, of the sums of the luminance level differences developed every said plural arbitrary areas, which are outputted from the integration circuit; wherein the minimum value output circuit comprises: a control circuit which outputs a prelatch signal with a timing provided to calculate the whole sum of luminance level differences every said arbitrary area, a pulse generator which outputs a latch signal with same timing as the prelatch signal when the detection signal is not outputted, and stops the output of the latch signal when the detection signal is outputted, a selection circuit which compares the sums of the luminance level differences developed every said arbitrary area, which are supplied to a first input side from the integration circuit, and a value supplied to a second input side, and selects and outputs smaller values, and a register to which a maximum value is set as an initial value, said register sequentially holding the smaller values selected and outputted from the selection circuit in accordance with the latch signal and supplying the same to the second input side of the selection circuit to thereby update the held values, and outputting the sum of the luminance level differences, which is minimum within said arbitrary areas, as the quality of noise.