Method for preventing the deterioration of picture quality in a video processor and circuit thereof

A method for preventing the deterioration of picture quality in a video processor which has a combfilter for separating a video signal, which contains a burst signal and which is low-pass-filtered to prevent aliasing, into luminance and chrominance signals and uses a clock signal to process a signal for said combfilter, said method comprising the steps of:

• discriminating whether said video signal is a color signal or a mono signal;
• gating the burst signal contained on the input video signal;
• outputting said clock signal locked by a reference signal to said combfilter;
• outputting a feedback signal by delaying said clock signal for a predetermined period;
• and
• selecting the burst signal of said burst signal gating step when the color signal is discriminated in said signal discriminating step, and selecting the feedback signal of said clock signal outputting step when the mono signal is discriminated in said signal discriminating step, so as to send the selected signal as said reference signal of said clock signal outputting step,
• whereby a constant clock signal is generated regardless of whether the input video signal is the color signal or the mono signal, so as to prevent aliasing due to clock variations created when the mono signal without the burst signal is input.

A circuit for preventing the deterioration of picture quality in a video processor which has a combfilter for separating a video signal, which contains a burst signal, into luminance and chrominance signals, a clock signal being used to process a signal through said combfilter, said circuit comprising:

• a color/mono discriminator which discriminates whether the video signal is a color signal or a mono signal according to the presence or absence of the burst signal in the video signal;
• a burst-locked clock generator for generating said clock signal according to the burst signal which is taken as a reference signal;
• a generator for generating a quasi-burst signal by delaying said clock signal for a predetermined period;
• and
• an output device for outputting the burst signal contained on the video signal or the quasi-burst signal to said burst-locked clock generator as the reference signal, according to the discriminated result of said color/mono discriminator,
• whereby a constant clock signal is generated regardless of whether the input video signal is the color signal or the mono signal, so as to prevent high-band noise due to clock variations created when the mono signal without the burst signal is input.

A circuit for preventing the deterioration of picture quality in a video processor which has a combfilter for separating a video signal, containing a burst signal, which is low-pass-filtered to prevent aliasing into luminance and chrominance signals, a clock signal being used to process a signal through said combfilter, said circuit comprising:

• means for discriminating whether the video signal is a color signal or a mono signal according to the presence or absence of the burst signal;
• means for gating the burst signal loaded on the input video signal;
• means for generating and outputting said clock signal having a predetermined frequency locked by a reference signal to said combfilter;
• means for outputting a feedback signal by delaying said output clock signal for a predetermined period;
• and
• means for selecting the burst signal of said burst signal gating means when the video signal is a color signal or selecting the feedback signal of said feedback signal output means when the video signal is a mono signal, according to the discriminated result of said discriminating means, and outputting the selected signal as said reference signal of said clock signal generating means,
• whereby a constant clock signal is generated regardless of whether the input video signal is the color signal or the mono signal, so as to prevent aliasing due to clock variations created when the mono signal without the burst signal is input.

A circuit for preventing the deterioration of picture quality in a video processor which receives an analog video signal, the circuit comprising:

• a filter for low-pass-filtering an input video signal so as to remove noise due to the high-band component of the video analog signal;
• analog-to-digital (A/D) converter for converting said low-pass-filtered video analog signal into a digital video signal;
• a combfilter for separating said digital video signal containing an input burst signal into digital luminance and chrominance signals using a clock signal;
• a digital-to-analog (D/A) converter for converting the digital luminance and chrominance signals output from said combfilter into analog luminance and chrominance signals;
• a burst signal gate for detecting a burst signal from the input video signal;
• clock signal generator for outputting a clock signal having a predetermined frequency locked by a reference signal as the sampling clock signal of said A/D converter and D/A converter, and simultaneously outputting the clock signal to said combfilter as a signal-processing clock signal;
• delay unit for delaying the clock signal generated by said clock signal generator and outputting a feedback signal;
• a discriminator for discriminating whether the input video signal is a color signal or a mono signal;
• and
• a selection unit for selecting the burst signal when the video signal is the color signal or selecting the feedback signal when the video signal is the mono signal, according to the discriminated result of said discriminator, and outputting the selected signal as said reference signal of said clock signal generator,
• whereby a constant clock signal is generated regardless of whether the input video signal is the color signal or the mono signal, so as to prevent aliasing due to clock variations created when the mono signal without the burst signal is input.

A method for preventing the deterioration of picture quality in a video processor which includes at least one filter and at least one converter which operate according to a generated frequency signal, the method comprising the steps of:

• receiving a video signal;
• determining whether the received video signal includes a burst signal;
• and
• modifying the generated frequency signal according to the burst signal when it is determined by said determining step that the received video signal include the burst signal, and modifying the generated frequency signal according to a previously generated frequency signal when it is determined by said determining step that the received video signal does not include the burst signal.