Patent ID: 7046298

Claim:
A data signal extraction apparatus that extracts a predetermined data signal from an inputted video signal that is serially transmitted from outside, comprising: an A/D conversion unit for sampling the inputted video signal based on a sampling clock of a predetermined frequency, to be converted into a digital video signal; a slice level calculation unit for calculating a slice level that is used to evaluate a value of the inputted video signal as 0 or 1, on the basis of the digital video signal; a binarization unit for converting the digital video signal into a binary signal using the slice level; an extraction interval calculation unit for calculating an extraction interval value to extract the predetermined data signal from the digital video signal; a zero-crossing point detection unit for detecting a zero-crossing point at which the binary signal changes from 0 to 1, or from 1 to 0; a phase shift amount calculation unit for calculating an amount of phase shift in the data signal, on the basis of the zero-crossing point; a correction amount calculation unit for calculating an amount of correction for the extraction interval value, according to the phase shift amount; an extraction interval correction unit for correcting the extraction interval value according to the correction amount, to obtain a corrected extraction interval value; an extraction pulse generation unit for calculating a position of the data signal in the binary signal successively from a predetermined extraction position, being spaced at intervals that are close to the corrected extraction interval value, and generating an extraction pulse designating the position of the data as a data extraction position; and an extraction unit for extracting the data signal from the binary signal in accordance with the extraction pulse.