EP0601655A1
Expired / Lapsed
EP
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Noise reduction filter
Assignee: Koninklijke Philips NV
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Filing: 1993-12-03
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Granted: —
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Expires: 2013-12-03
Abstract
Abstract In a noise reduction filter comprising a weighted average filter (1A) coupled to receive a plurality of input signal samples (O,⊕) and furnishing noise-reduced signal samples, and a delay circuit (3A) which is coupled to an output of the weighted average filter (1A) and which furnishes a plurality of delayed noise-reduced signal samples (X) to a further input of the weighted average filter (1A), weighting coefficients assigned to samples of said input signal (O) and said delayed signal (X) depend on respective differences between a current sample (⊕) of said input signal on the one hand and said samples of said input signal (O) and said delayed signal (X) on the other hand.
Inventors
- 👤 Gerard De Haan
- 👤 Paul Willem Albert Cornelis Biezen
- 👤 Olukayode Anthony Ojo
- 👤 Tatiana Georgieva Kwaaitaal-Spassova
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 19:03
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/21; H04N9/00; H04N9/64; H04N9/646
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
105 words
A noise reduction filter comprising: delay means (3) for furnishing a plurality of delayed signal samples (X); a weighted average filter (1) coupled to receive a plurality of input signal samples (O,⊕) and said delayed signal samples (X) to furnish noise-reduced signal samples to said delay means (3), and wherein weighting coefficients assigned to samples (Pn₁..Pn n ) of said input signal (O) and said delayed signal (X) depend on respective differences between a current sample (⊕,Pc) of said input signal on the one hand and said samples (Pn₁..Pn n ) of said input signal (O) and said delayed signal (X) on the other hand.
Claim 2
Dependent Claim
46 words
A noise reduction filter as claimed in claim 1, wherein said plurality of input samples (O,⊕) are all on a first horizontal line of an image signal, while said delayed signal samples (X) are all on one or more lines other than said first horizontal line.
Claim 3
Dependent Claim
89 words
A noise reduction filter as claimed in claim 1, wherein a first weighting coefficient is assigned to samples (Pn₁..Pn n ) of said input signal (O) and said delayed signal (X) differing by less than a threshold value from said current sample (⊕,Pc) of said input signal, while weighting coefficients differing from said first weighting coefficient are assigned to samples (Pn₁..Pn n ) of said input signal (O) and said delayed signal (X) differing by more than said threshold value from said current sample (⊕,Pc) of said input signal.
Claim 4
Dependent Claim
61 words
A noise reduction filter as claimed in claim 3, wherein a second weighting coefficient smaller than said first weighting coefficient is assigned to those samples (Pn₁..Pn n ) which differ from the current sample (⊕,Pc) by more than said first-mentioned threshold value and by less than a second threshold value, which second threshold value is larger than said first threshold value.
Claim 5
Dependent Claim
19 words
A noise reduction filter as claimed in claim 1, wherein said delay means (3) comprise motion vector compensation means.
Claim 6
Dependent Claim
18 words
A noise reduction filter as claimed in claim 3, wherein said threshold value depends on the noise level.
Claim 7
Dependent Claim
28 words
A noise reduction filter as claimed in claim 3, wherein said threshold value depends on a minimum in a field of a motion-compensated difference between two successive fields.
Claim 8
Dependent Claim
27 words
A noise reduction filter as claimed in claim 1, wherein weighting coefficients for a chrominance signal noise reduction filtering depend on differences between neighboring luminance sample values.
Claim 9
Dependent Claim
26 words
A noise reduction filter as claimed in claim 1, wherein said samples (Pn₁..Pn n ) applied to said weighting average filter (1) are not-directly neighboring samples.
Claim 10
Dependent Claim
42 words
A noise reduction filter as claimed in claim 9, wherein a distance between said not-directly neighboring samples depends on an edge-detection such that said distance decreases with an increasing difference between a current sample (⊕,Pc) and one of said not-directly neighboring samples.
Claim 11
Dependent Claim
28 words
A noise reduction filter as claimed in claim 1, wherein said delayed samples (X) from a previous line are taken from positions line-alternatingly shifted in the horizontal direction.
Claim 12
Dependent Claim
48 words
An image signal receiver comprising a signal input for receiving an image signal, a signal processor for processing said image signal, and a display unit for displaying the processed image signal, wherein said signal processor comprises a noise reduction filter as claimed in any of the preceding claims.
Claim 13
Dependent Claim
113 words
A noise reduction filtering method comprising the steps of: furnishing (3) a plurality of delayed signal samples (X); assigning weighting coefficients to samples (Pn₁..Pn n ) of an input signal (O) and said delayed signal (X) in dependence on respective differences between a current sample (⊕,Pc) of said input signal on the one hand and said samples (Pn₁..Pn n ) of said input signal (O) and said delayed signal (X) on the other hand; and weighted average filtering (1) a plurality of said input signal samples (O,⊕) and said delayed signal samples (X) by means of said weighting coefficients to furnish noise-reduced signal samples to said delayed signal samples (X) furnishing step (3).
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