Adaptive comb filter

Claim 2

A filter according to claim 1, wherein low-pass filtering and interpolation are executed from a direction where a degree of change of a picture signal level around said given said picture elements is an average value.

Claim 3

A filter according to claim 1, wherein pre-low-pass filtering and interpolation filter processing are executed utilizing a degree of change of picture signal level around said given picture element on the basis of space and time, and wherein same picture element position is alternately subjected to subnyquist sampling in a plurality of frame periods.

Claim 4

A filter according to claim 1, wherein an absolute value of difference between two adjacent picture elements in each direction is employed as a degree of change of picture signal level in the periphery of said picture elements.

Claim 5

A filter according to claim 1, further comprising adaptive prefilter means for executing second-order low-pass filtering on a center picture element with the picture signals of the adjacent two pairs of picture elements in such a direction that a degree of change of picture signal level around said center picture element is a minimum, and adaptive interpolation filter means operating in response to an average value of a picture signal of an adjacent two pairs of picture elements in such a direction that a degree of change of picture signal level in the periphery of picture elements allowing subtraction of picture elements by said subsampler as the interpolation signal.

Claim 6

A filter for a digitized color television signal, comprising means for determining a direction from a given image point in said color television signal in which a minimum amount of change occurs over a predetermined distance; and means for performing a predetermined filtering operation on said color television signal in response to said determination.

Claim 7

The filter of claim 6, wherein said predetermined filtering operation comprises separating a luminance signal and a chrominance signal from said color television signal.

Claim 8

The filter of claim 6, wherein said predetermined filtering operation comprises subnyquist filtering of said color television signal having a portion of the information content thereof removed.

Claim 9

An adaptive comb filter for separating a luminance signal and a chrominance signal from a composite color television signal, comprising: A/D converter means for sampling said composite color television signal at a sampling frequency four times a color subcarrier frequency of said television signal to digitize the latter, delay means, a control circuit and a vertical/horizontal selecting filter, said delay means comprising means for extracting from a digitized television signal a signal S(i,j-1) at an i-th sampling point in a (j-1)-th the line of horizontal scanning lines on a field, a signal S(i,j) at an i-th sampling point in a j-th line, said signal S(i,j) being different in color subcarrier phase from said signal S(i,j-1) by 180°, signals S(i+2,j) and S(i-2,j) at (i+2)th and (i-2)th sampling points in said j-th line, said signals S(i+2,j) and S(i-2,j) being different in color subcarrier phase from said signal S(i,j) by 180°, and a signal S(i,j+1) at an i-th sampling point in a (i+1)th scanning line, said signal S(i,j+1) being different in color subcarrier phase from said signal S(i,j) by 180°, said control circuit comprising means for calculating an absolute value V of a difference between said signals S(i,j-1) and S(i,j+1) and an absolute value H of a difference between said signals S(i+2,j) and S(i-2,j), and means for comparing said absolute value V with said absolute value H, said vertical/horizontal selecting filter comprising means for calculating a luminance signal component Y(i,j) and a chrominance signal component C(i,j) of said signal S(i,j) according to the following equations when said absolute value V is smaller than said absolute value H: Y(i,j) =    (1/2){S(i,j) + (1/2)[S(i,j-1) + S(i,j+1)]} C(i,j) =    (1/2){S(i,j) - (1/2)[S(i,j-1) + S(i,j+1)]}, and calculating a luminance signal component Y(i,j) and chrominance signal component C(i,j) of said signal S(i,j) according to the following equations when said absolute value H is equal to or smaller than said absolute value V: Y(i,j) =    (1/2){S(i,j) + (1/2)[S(i-2,j) + S(i+1,j)]} C(i,j) =    (1/2){S(i,j) - (1/2)[S(i-2,j) + S(i+2,j)]}.

Claim 10

An adaptive comb filter comprising: a variable delay circuit for extracting simultaneously from a signal obtained by synchronously sampling an NTSC composite color television signal with a sampling frequency four times a color subcarrier frequency thereof a pair of horizontal sample signals in one scanning line, said horizontal sample signals being separated from a given sample signal in said one scanning line by two sample signals in opposite respective directions, said horizontal sample signals being different in color subcarrier phase from said given sample signal by 180° and a pair of vertical sample signals in scanning lines immediately above and below said one scanning line, said vertical sample signals being different in phase from said one sample signal by 180°, and means for extracting simultaneously from a signal obtained by synchronously sampling a PAL composite color television signal with a sampling frequency four times a color subcarrier frequency thereof a pair of horizontal sample signals in one scanning line, said horizontal sample signals being separated from a given sample signals in said one scanning line by two sample signals in opposite directions, said horizontal sample signals being different in color subcarrier phase from said given sample signal by 180°, and a pair of vertical sample signal in scanning lines above and below said one scanning line, said vertical sample signals being different in phase from said given sample signal by 180°, a comparator for comparing an absolute value of a difference between said horizontal sample signals with an absolute value of a difference between said vertical sample signals to determine which absolute value is the smaller, a vertical separation filter constituting a secondary digital filter for providing a luminance signal and a chrominance signal separately through predetermined operations on said horizontally adjacent sample signals, a vertical separation filter constituting a secondary digital filter for providing a luminance signal and a chrominance signal separately through predetermined operations on said vertically adjacent sample signals, and a selector responsive to a determination output of said comparator for selecting one of said separation filters, said luminance and chrominance outputs from said selected separation filter being used as a luminance signal output and a chrominance signal output of said adaptive comb filter.

Claim 11

An adaptive comb filter comprising: a variable delay circuit for extracting simultaneously from a signal obtained by synchronously sampling an NTSC composite color television signal with sampling frequency four times a color subcarrier frequency thereof a pair of horizontal sample signals in one scanning line, said horizontal sample signals being separated from a given sample signal in said one scanning line by two sample signals in opposite respective directions, said horizontal sample signals being different in color subcarrier phase from said certain sample signal by 180°, and a pair of vertical sample signals in scanning lines immediately above and below said one scanning line, said vertical sample signals being different in phase from said given sample signal by 180°, a comparator for comparing an absolute value or a difference between said horizontal sample signals with an absolute value of a difference between said vertical sample signals to determine which absolute value is the smaller, a horizontal separation filter constituting a secondary digital filter for providing a luminance signal and a chrominance signal separately through predetermined operations on said horizontally adjacent sample signals, a vertical separation filter constituting a secondary digital filter for providing a luminance signal and a chrominance signal separately through predetermined operations on said vertically adjacent sample signals, and a selector responsive to a determination output of said comparator for selecting one of said separation filters, said luminance and chrominance outputs from said selected separation filter being used as a luminance signal output and a chrominance signal output of said adaptive comb filter.

Claim 12

An adaptive comb filter comprising: a variable delay circuit for extracting simultaneously from a signal obtained by synchronously sampling frequency four times a color subcarrier frequency thereof a pair of horizontal sample signals in one scanning line, said horizontal sample signals being separated from a given sample signal in said one scanning line by two sample signals in opposite directions, said horizontal sample signals being different in color subcarrier phase from said given sample signal by 180°, and a pair of vertical sample signals in scanning lines above and below said one scanning line, said vertical sample signals being different in phase from said given sample signal by 180°, a comparator for comparing an absolute value of a difference between said horizontal sample signals with an absolute value of a difference between said vertical sample signals to determine which absolute value is the smaller, a horizontal separation filter constituting a secondary digital filter for providing a luminance signal and a chrominance signal separately through predetermined operations on said horizontally adjacent sample signals, a vertical separation filter constituting a secondary digital filter for providing a luminance signal and a chrominance signal separately through predetermined operations on said vertically adjacent sample signals, and a selector responsive to a determination output of said comparator for selecting one of said separation filters, said luminance and chrominance outputs from said selected separation filter being used as a luminance signal output and a chrominance signal output of said adaptive comb filter.

Claim 13

A luminance and chrominance signal separation filter comprising: vertical filter means for determining one-fourth of a result obtained by subtracting a sum of a data signal S -v occurring in the same line as a data signal S₀ in the line one line before said data signal S₀ and the data signal S + allocated in the same line as a data signal S₀ in the line one line after the said data signal S₀ from two times said data signal S₀ for a data signal digitized at a sampling frequency which is equal to 2k times a color subcarrier frequency, (where k is a positive integer) from an NTSC composite color television signal; transversal filter means for determining one-fourth of a result obtained by subtracting a sum of a data signal S -h specified sampling points before the said data signal S₀ in the same line as said data signal and a data signal S +h specified sampling points after said data signal S₀ from two times of said data signal S₀; comparator means for comparing an absolute value D v of a difference between said data signals S -v and S +v (D V =|S -v - S +v |) and an absolute value D h of said data signals S -h and S +h (Dh = |S-h - S+h|); selector means for outputting one of an output of said vertical filter and an output of said transversal filter selected in accordance with a comparison result of said comparator means; and bandpass filter means responsive to an output of said selector means for outputting only a specified frequency band around said color subcarrier frequency.

Claim 14

A luminance and chrominance signal separation filter comprising: a vertical filter means for determining one-fourth of a result obtained by subtracting a sum of a data signal P -V occurring in the same line as a data signal P₀ in the line two lines before said data signal P₀ and the data signal P +V allocated in the same line as a data signal P₀ in the line two lines after the said data signal P₀ from two times said data signal P₀ for the data signals digitized at a sampling frequency which is equal to 2k times a color subcarrier frequency (where k is a positive integer) from a PAL composite color television signal; transversal filter means for determining one-fourth of a result obtained by subtracting a sum of a data signal P -h specified sampling points before the said data signal P₀ in the same line as said data signal P₀ and data signal P +h specified sampling points after said data signal P₀ from two times said data signal P₀; comparator means for comparing an absolute value D vp of said data signals P -y and P +v (D vp = | P -v - P +v |) and an absolute value D hp of said data signals P -h and P +h (D hp =|P -h - P +h |); selector means for outputting one of an output of said vertical filter and an output of said transversal filter selected in accordance with a comparison result of said comparator means; and bandpass filter means responsive to an output of said selector means for outputting only a specified frequency band around said color subcarrier frequency.