Patent ID: 7894705
Filing Date: 2011-02-22
Classification: H04N

Abstract:
1. A phase-locked loop (PLL) controller for obtaining a phase error between a period of a horizontal sync signal in an input video signal and a reference period of a reference signal, filtering the phase error, and multiplying a result of filtering by a predetermined multiplier coefficient by a multiplier to control a phase-locked loop, comprising: a counter for receiving a vertical sync signal in the input video signal to count a number of lines for one field; a first detector for special reproduction of a video cassette player for utilizing a characteristic of the special reproduction signal of a video cassette player to determine whether or not the input video signal is a special reproduction signal of a video cassette player to produce a first detection result indicating whether or not the special reproduction signal of a video cassette player is detected; a second detector for normal reproduction of a video cassette player for utilizing a characteristic of the normal reproduction signal of a video cassette player to determine whether or not the input video signal is a normal reproduction signal of a video cassette player to produce a second detection result indicating whether or not the normal reproduction signal of a video cassette player is detected; a third detector for weak electric field of television for detecting whether or not the input video signal is a weak electric field signal of television to produced a third detection result indicating whether or not the weak electric field signal of television is detected; and a coefficient selector operative in response to the first, second and third detection results for detecting the predetermined multiplier coefficient, wherein, said first detector compares the number of lines input from said counter with the number of lines for one field in a normal video signal, thereby detecting the special reproduction signal of a video cassette player when both numbers of lines differ from each other, and, otherwise, producing the first detection result indicating that no special reproduction signal is detected; said second detector detecting a vertical blanking period and a position of a vertical sync pulse in the input video signal on a basis of the number of lines input from said counter, and determining, if a present line is during the vertical blanking period and before the vertical sync pulse, whether or not the phase error is large, thereby detecting the normal reproduction signal when the phase error is detected large, and, otherwise, producing the second detection result indicating that no normal reproduction signal is detected; said third detector tracking the phase error on a line-to-line basis to detect an error-fluctuating period, including an error with a longer period together with an error with a shorter period, said detector, said third detector detecting the weak electric field signal of television when the error-fluctuating period is detected over a predetermined times during one field period on a basis of the number of lines input from said counter, and, otherwise, producing the third detection result indicating that no weak electric field signal of television is detected, and the predetermined multiplier coefficient detected by said coefficient selector is provided to the phase-locked loop to thereby control a change of a tracking rate of said phase-locked loop.