Patent ID: 6664977
Filing Date: 2003-12-16
Classification: G09G

Abstract:
A video signal processing device for displaying, on a display, pixels in a video signal inputted from an image signal source, said video signal processing device comprising:a clock delay circuit operable to receive a reference signal, and delay the reference signal by an odd number of clocks for output as a clock output signal; a multiplexer operable to select either the reference signal or the clock output signal from said clock delay circuit for output as a multiplexer output signal; an A/D converter operable to convert the video signal into a digital signal for two-phase output including first phase data and second phase data with reference to the multiplexer output signal from said multiplexer; a first leading edge detection circuit operable to detect a leading edge of a first valid video signal region in the first phase data, and output a first detection signal corresponding thereto; a second leading edge detection circuit operable to detect a leading edge of a second valid video signal region in the second phase data, and output a second detection signal corresponding thereto; a first back porch detection circuit for detecting a first back porch period starting from the multiplexer output signal from said multiplexer to the first detection signal outputted from said first leading edge detection circuit; a second back porch detection circuit for detecting a second back porch period starting from the multiplexer output signal from said multiplexer to the second detection signal outputted from said second leading edge detection circuit; and a comparator operable to compare the first back porch period and the second back porch period, and when the first back porch period is longer than the second back porch period, determine that head data in a third valid video signal region in the video signal is not included in the first phase data, and output a signal to control said multiplexer to switch the multiplexer output signal therefrom.