Patent EP0279702A2 successfully refreshed from Google Patents.
EP0279702A2
Expired / Lapsed
EP
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Signal processing methods and apparatus in quadrature-modulated subcarrier color television systems using adaptive threshold
Assignee: Individual
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Filing: 1988-02-19
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Granted: —
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Expires: 2008-02-19
Abstract
Abstract A comb filter for improved cross-color reduction with improved visible diagonal resolution is provided for processing a luminance component of a quadrature modulated color subcarrier television signal in the vicinity of the color subcarrier pass band. The comb filter comprises an input and an output, and has a first path including a delay circuit for delaying the luminance component and a subtraction circuit connected between the input and the output, and has a second path including a chrominance type comb filter, a band pass filter for passing a spectrum in the vicinity of the color subcarrier pass band both being followed by a variable threshold circuit connected to the subtraction circuit. The variable threshold circuit is for inhibiting the signal in the second path below a variable threshold. The variable threshold is derived as a function of at least one of luminance diagonal transition level, chroma level and averaged luminance activity in the spectrum in the vicinity of the color subcarrier.
Inventors
- 👤 Yves Charles Faroudja
- 👤 Jack James Campbell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 21:46
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/646
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
143 words
A comb filter for processing a luminance component of a quadrature modulated color subcarrier television signal in the vicinity of the color subcarrier pass band, the comb filter comprising an input and an output, and having a first path including a delay circuit for delaying the luminance component and a subtraction circuit connected between the input and the output, and a second path including a chrominance type comb filter, a band pass filter for passing a spectrum in the vicinity of the color subcarrier pass band followed by variable threshold circuit means connected to the subtraction circuit, the variable threshold circuit means for inhibiting the signal in the second path below a variable threshold being derived as a function of at least one of luminance diagonal transition level, chroma level and luminance activity in the spectrum in the vicinity of the color subcarrier.
Claim 2
Dependent Claim
143 words
A comb filter for processing a luminance component of a quadrature modulated color subcarrier television signal in the vicinity of the color subcarrier pass band, the comb filter comprising an input and an output, and having a first path including a delay circuit for delaying the luminance component and a subtraction circuit connected between the input and the output, and a second path including a chrominance type comb filter, a band pass filter for passing a spectrum in the vicinity of the color subcarrier pass band followed by variable threshold circuit means connected to the subtraction circuit, the variable threshold circuit means for inhibiting the signal in the second path below a variable threshold being derived as a function of at least one of luminance diagonal transition level, chroma level and luminance activity in the spectrum in the vicinity of the color subcarrier.
Claim 3
Dependent Claim
21 words
The comb filter set forth in claim 1 contained within a color encoder within a quadrature modulated color subcarrier television system.
Claim 4
Independent Claim
177 words
A method for controlling the operation of a luminance comb filter in a color television system including the steps of: chrominance-type comb filter processing of at least that portion of a luminance component of a quadrature modulated color subcarrier television signal filter interleaved in the spectrum of the color subcarrier pass band and band pass filtering the luminance component to limit it to the spectrum of said color subcarrier pass band to provide a band pass filtered and combed luminance component, subjecting the band pass filtered and combed luminance component to a variable threshold below which said band pass filtered and combed luminance component is inhibited and above which said band pass filtered and combed luminance component is passed, subtracting said band pass filtered and combed luminance component as passed by said variable threshold from a delay matched original luminance component to provide a combed original luminance component whenever said band pass filtered and combed luminance component is passed and a non-combed original luminance component whenever said band pass filtered and combed luminance component is not passed.
Claim 5
Independent Claim
177 words
A method for controlling the operation of a luminance comb filter in a color television system including the steps of: chrominance-type comb filter processing of at least that portion of a luminance component of a quadrature modulated color subcarrier television signal filter interleaved in the spectrum of the color subcarrier pass band and band pass filtering the luminance component to limit it to the spectrum of said color subcarrier pass band to provide a band pass filtered and combed luminance component, subjecting the band pass filtered and combed luminance component to a variable threshold below which said band pass filtered and combed luminance component is inhibited and above which said band pass filtered and combed luminance component is passed, subtracting said band pass filtered and combed luminance component as passed by said variable threshold from a delay matched original luminance component to provide a combed original luminance component whenever said band pass filtered and combed luminance component is passed and a non-combed original luminance component whenever said band pass filtered and combed luminance component is not passed.
Claim 6
Dependent Claim
43 words
The method set forth in claim 3 comprising the further step of deriving said variable threshold as a function of at least one of luminance diagonal transition level, chroma level and luminance activity in the spectrum in the vicinity of the color subcarrier.
Claim 7
Dependent Claim
64 words
The method set forth in claim 4 wherein the step of deriving said variable threshold level is carried out by deriving chroma level as one of the square root of the sum the squares of two color matrix signals, the greater of the absolute values of said two color matrix signals, and the sum of the absolute values of said two color matrix signals.
Claim 8
Dependent Claim
25 words
The method set forth in claim 5 applied to an NTSC format color television signal wherein the two color matrix signals are I and Q.
Claim 9
Dependent Claim
25 words
The method set forth in claim 5 applied to a PAL format color television signal wherein the two color matrix signals are U and V.
Claim 10
Dependent Claim
21 words
The method set forth in claim 3 carried out within an encoding process in a quadrature modulated color subcarrier television system.
Claim 11
Independent Claim
194 words
A method for processing a color television picture signal including a luminance component and a color component which is amplitude modulated in phase quadrature upon a suppressed subcarrier, to reduce cross-color and cross-luminance artifacts in a resultant signal, including the steps of: comb filtering the quadrature modulated color component to put out a comb filtered chroma component; processing the luminance component by passing the luminance component through two complementary filters both symmetrically centered about a color component subcarrier frequency, one filter comprising a band pass filter and the other filter comprising a band reject filter; developing a variable threshold control signal based on luminance diagonal transition level, chroma level and luminance activity in the 2.5 to 4.5 MHz area; comb filtering the luminance signal passing through the band pass filter in those instances when the threshold control signal is present; and, adding in phase the above-threshold, comb filtered luminance signal and the signal passing through the band reject filter in order to provide a comb filtered full bandwidth luminance signal; and, combining in phase the comb filtered chroma component and the comb filtered full bandwidth luminance signal in order to provide the resultant signal.
Claim 12
Independent Claim
194 words
A method for processing a color television picture signal including a luminance component and a color component which is amplitude modulated in phase quadrature upon a suppressed subcarrier, to reduce cross-color and cross-luminance artifacts in a resultant signal, including the steps of: comb filtering the quadrature modulated color component to put out a comb filtered chroma component; processing the luminance component by passing the luminance component through two complementary filters both symmetrically centered about a color component subcarrier frequency, one filter comprising a band pass filter and the other filter comprising a band reject filter; developing a variable threshold control signal based on luminance diagonal transition level, chroma level and luminance activity in the 2.5 to 4.5 MHz area; comb filtering the luminance signal passing through the band pass filter in those instances when the threshold control signal is present; and, adding in phase the above-threshold, comb filtered luminance signal and the signal passing through the band reject filter in order to provide a comb filtered full bandwidth luminance signal; and, combining in phase the comb filtered chroma component and the comb filtered full bandwidth luminance signal in order to provide the resultant signal.
Claim 13
Dependent Claim
21 words
The method set forth in claim 9 carried out within an encoding process in a quadrature modulated color subcarrier television system.
References Cited (Backward Citations)
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