Patent ID: 6606410
Filing Date: 2003-08-12
Classification: H04N

Abstract:
A method for determining if a synchronous signal is contained in an input image signal, comprising the steps of:(a) establishing a vertical period during which vertical synchronous signal pulses contained in said input image signal are counted; (b) establishing a minimum vertical value and a maximum vertical value which correspond to a proper number of said vertical synchronous signal pulses contained in said vertical period; (c) establishing a minimum noise count value and a maximum noise count value which correspond to a number of noise pulses that are estimated to be similar to said vertical synchronous signal pulses in a noise gate pulse period; (d) generating a noise gate pulse between adjacent pulses of said vertical synchronous signal pulses; (e) counting a first number of said vertical synchronous signal pulses during said vertical period to obtain a first counted value; (f) determining if said first counted value is greater than or equal to said minimum vertical value and less than or equal to said maximum vertical value; and (g) generating a negative determination signal as a current determination signal when said first counted value is less than or equal to said minimum vertical value or is greater than or equal to said maximum vertical value, wherein said negative determination signal indicates that an actual synchronous signal is not contained in said input image signal; (h) counting a second number of said noise pulses during said noise gate pulse period to obtain a second counted value; and (i) generating a positive determination signal as said current determination signal when said first counted value is greater than or equal to said minimum vertical value and less than or equal to said maximum vertical value and when said second counted value is less than said minimum noise count value, wherein said positive determination signal indicates that an actual synchronous signal is contained in said input image signal.