Sync signal generating apparatus and method for a video signal processor

A method for generating sync signal for a video signal processor, comprising the steps of:

• determining the frame rate of an input image signal;
• determining whether an image to be displayed is a digital image or an analog image, and generating a display mode signal;
• generating a clock signal according to the display mode signal and the frame rate signal;
• generating a sync compensation signal based upon the display mode signal, the clock signal and an NTSC sync signal, and
• compensating a sync signal according to the sync compensation signal and outputting a compensated sync signal.

A video signal processor, comprising:

• a video decoder decoding the input compressed digital image signal and outputting a digital image signal;
• an analog processor processing the input analog signal and outputting an analog vsync signal and an analog hsync signal;
• an image processor processing to display either the digital input image signal or the analog the input image signal according to a clock signal;
• a frame detector determining the frame rate of an input image signal;
• a display mode detector determining whether an image to be displayed is a digital image or an analog image, and generating a display mode signal;
• a clock generator generating the clock signal according to the display mode signal and the frame rate signal;
• a sync signal compensation unit generating a sync compensation signal based upon the display mode signal, the clock signal, and an NTSC sync signal, and
• a sync signal generator compensating a sync signal according to the sync compensation signal and outputting a compensated sync signal.