Digital comb filtering for PAL television signals

A method of correcting the phase of the color component of a reference picture element in a reference frame of a PAL type television signal, comprising:

• (a) sampling the television signal at a rate corresponding to N times the chroma subcarrier frequency of the television signal, where N is an even integer, thereby to generate a series of digital signals each associated with a discrete picture element and each representative of the amplitude of the luminance component and amplitude and phase of the chroma component of its associated picture element;
• (b) storing the digital signals associated with the picture elements of a reference line (n) of a reference frame of the television signal, and storing the digital signals associated with the picture elements in lines (n+1) and (n-1) immediately preceding and following the reference line (n), respectively;
• and
• (c) detecting motion and the lack thereof occurring in that part of the television signal associated with stored digital signals;
• (d) generating a resultant chroma signal by combining and averaging stored digital signals associated with selected picture elements in only one of the lines (n-1) and (n+1) when such motion is detected, and combining and averaging stored digital signals associated with selected picture elements in both the lines (n-1) and (n+1) when no such motion is detected, said combining and averaging being effected such that the resultant chroma signal is substantially free of luminance components and has substantially the same amplitude and phase as that of a picture element which is in the next successive frame immediately following the reference frame and whose location corresponds to the location of the reference picture element;
• (e) generating a resultant luminance signal by combining and averaging stored digital signals associated with selected picture elements in at least two of the lines (n), (n+1), and (n-1) when no motion is detected, and by combining and averaging stored digital signals associated with selected picture elements in only one of the lines (n), (n+1), and (n-1) when motion is detected, said combining and averaging being effected such that the resultant luminance signal is substantially free of chroma components;
• and
• (f) combining the resultant luminance signal with the resultant chroma signal to develop a final signal.

A comb filter for correcting the phase of the color component of a reference picture element in a reference frame of a PAL type television signal, comprising:

• means for sampling the television signal at a rate corresponding to N times the chroma subcarrier frequency of the television signal, where N is an even integer, thereby to generate a series of digital signals each associated with a discrete picture element and each representative of the amplitude of the luminance component and amplitude and phase of the chroma component of its associated picture element;
• means for storing the digital signals associated with the picture elements of a reference line (n) of a reference frame of the television signal, and storing the digital signals associated with the picture elements in lines (n+1) and (n-1) immediately preceding and following the reference line (n), respectively;
• and
• means for combining and averaging stored digital signals associated with selected picture elements in at least one of the lines (n-1) and (n+1) such that the resultant chroma signal is substantially free of luminance components and has substantially the same amplitude and phase as that of a picture element which is in the frame (n-1) immediately following the reference frame and whose location corresponds to the location of the reference picture element,
• whereby the amplitude and phase of the chroma components of correspondingly located picture elements in successive frames are rendered substantially the same for comparison with each other.

A comb filter for correcting the phase of the color component of a reference picture element in a reference frame of a PAL type television signal, comprising:

• means for sampling the television signal at a rate corresponding to N times the chroma subcarrier frequency of the television signal, where N is an even integer, thereby to generate a series of digital signals each associated with a discrete picture element and each representative of the amplitude of the luminance component and amplitude and phase of the chroma component of its associated picture element;
• means for storing the digital signals associated with the picture elements of a reference line (n) in a reference frame of the television signal, and storing the digital signals associated with the picture elements in lines (n+1) and (n-1) immediately preceding and following the reference line (n), respectively;
• motion sensing means for detecting motion and the lack thereof occurring in that part of the television signal associated with stored digital signals;
• means for generating a resultant chroma signal by combining and averaging stored digital signals associated with selected picture elements in only one of the lines (n-1) and (n+1) when such motion is detected, and combining and averaging stored digital signals associated with selected picture elements in both the lines (n-1) and (n+1) when no such motion is detected, sad combining and averaging being effected such that the resultant chroma signal is substantially free of luminance components and has substantially the same amplitude and phase as that of a picture element which is in the frame immediately following the reference frame and whose location corresponds to the location of the reference picture element;
• means for generating a resultant luminance signal by combining and averaging stored digital signals associated with selected picture elements in at least two of the lines (n), (n+1), and (n-1) when no motion is detected, and by combining and averaging stored digital signals associated with selected picture elements in only one of the lines (n), (n+1), and (n-1) when motion is detected, said combining and averaging being effected such that the resultant luminance signal is substantially free of chroma components;
• and
• means for combining the resultant luminance signal with the resultant chroma signal to develop a final signal.