Patent ID: 7193600

Claim:
A display device comprising: a clock generation circuit for generating sampling clocks, whose frequency is controlled on the basis of a required frequency control value, on the basis of a horizontal synchronizing signal of an input video signal; an analog-to-digital converter for sampling the input video signal on the basis of the sampling clocks generated from the clock generation circuit; horizontal video start position detection means for detecting a horizontal video start position of video data outputted from the analog-to-digital converter on the basis of a first threshold value; horizontal video end position detection means for detecting a horizontal video end position of the video data outputted from the analog-to-digital converter on the basis of a variable second threshold value; calculation means for calculating the number of sampling clocks corresponding to the distance from the horizontal video start position to the horizontal video end position; judgment means for judging whether or not the result of the calculation by the calculation means coincides with a required reference value; frequency control value adjustment means for calculating, when it is judged that the result of the calculation by the calculation means and the reference value do not coincide with each other, a new frequency control value on the basis of the result of the calculation by the calculation means, the reference value, and the frequency control value currently set in the clock generation circuit, to feed the new frequency control value to the clock generation circuit; and threshold value control means for controlling, for each vertical period, the variable second threshold value depending on the level of the video data at the horizontal video end position detected within the vertical period.