Noise reduction

Claim 2

A luminance signal noise reduction filter comprising: delay means for furnishing delayed signal samples (X); and a filter coupled to a signal input terminal to receive input luminance signal samples (∘,⊕) and to said delay means to receive said delayed signal samples (X) thereby to furnish noise-reduced signal samples, wherein all said signal samples (Pn 1 . . . Pn n ) applied to said filter are not-directly neighboring samples and said delayed samples (X) are from a previous line and are taken from positions line-alternatingly shifted in the horizontal direction.

Claim 3

A noise reduction filter as claimed in claim 1, further comprising an edge detector 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 4

A noise reduction filter as claimed in claim 1, wherein said input samples are all on one horizontal line of an image signal and said delayed signal samples are all on one or more liens other than said one horizontal line.

Claim 5

A noise reduction filter as claimed in claim 1, wherein said filter comprises a weighted average filter in which weighting coefficients assigned to samples (Pn 1 . . . 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 and said samples (Pn 1 . . . Pn n ) of said input signal (O) and said delayed signal (X) and a first weighting coefficient is assigned to samples (Pn 1 . . . 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, whereas weighting coefficients that differ from said first weighting coefficient are assigned to samples (Pn 1 . . . Pn n ) of said input signal (O) and said delayed signal (X) which differ by more than said threshold value from said current sample (⊕,Pc) of said input signal, said threshold value depending on a minimum in a field of a motion-compensated difference between two successive fields.

Claim 6

A noise reduction filter as claimed in claim 4, wherein a second weighting coefficient smaller than said first weighting coefficient is assigned to those samples (Pn 1 . . . 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 7

A noise reduction filter as claimed in claim 4, wherein said threshold value depends on the noise level.

Claim 8

A noise reduction filter as claimed in claim 4, wherein weighting coefficients for a chrominance signal noise reduction filtering depend on differences between neighboring luminance sample values.

Claim 9

A noise reduction filter as claimed in claim 1, wherein said delay means comprise motion vector compensation means.

Claim 10

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 claim 1.

Claim 11

A noise reduction filter comprising: an input terminal for receiving an input video signal made up of plural lines of pixels, a delay circuit, a first tapped pixel delay line, means coupling said delay circuit and said first tapped pixel delay line in cascade to said input terminal, an averaging circuit having a first plurality of inputs coupled to respective tap points on said first tapped pixel delay line so as to receive delayed pixels of a prior line of pixels wherein said delayed pixels are not directly neighboring pixels, a second tapped pixel delay line coupled to said input terminal and having tap points coupled to further respective inputs of the averaging circuit so as to supply the averaging circuit with pixels of a current line of pixels, and wherein said averaging circuit has an output terminal for supplying a filtered output video signal with reduced low frequency noise components.

Claim 12

A noise reduction filter comprising: an input terminal for receiving an input video signal made up of plural lines of pixels, a delay circuit, a first tapped pixel delay line, means coupling said delay circuit and said first tapped pixel delay line in cascade to said input terminal, an averaging circuit having a first plurality of inputs coupled to respective tap points on said first tapped pixel delay line so as to receive delayed pixels of a prior line of pixels wherein said delayed pixels are not directly neighboring pixels, a second tapped pixel delay line coupled to said input terminal and having tap points coupled to further respective inputs of the averaging circuit so as to supply the averaging circuit with pixels of a current line of pixels, and wherein said averaging circuit has an output terminal for supplying a filtered output video signal with reduced low frequency noise components.

Claim 13

The noise reduction filter as claimed in claim 10 wherein said delay circuit provides a one line delay so that said averaging circuit receives pixels from adjacent lines of said input video signal, said filter further comprising, switching means for selectively coupling said first plurality of inputs of the averaging circuit to selected tap points on said first tapped pixel delay line.

Claim 14

The noise reduction filter as claimed in claim 11 further comprising, an edge detector circuit coupled to said input terminal so as to derive a control signal determined by the distance between a current pixel sample and one of the not directly neighboring pixels, and means coupling said control signal to control inputs of given delay elements of said first and second tapped pixel delay lines so as to control said given elements whereby the distance between said not directly neighboring pixels decreases as the difference between said current pixel sample and said one not directly neighboring pixel increases.

Claim 15

The noise reduction filter as claimed in claim 12 wherein said first tapped pixel delay line comprises a plurality of one-pixel delay elements interspersed with said given delay elements which comprise switchable two-pixel delay elements, and said given delay elements of the second tapped pixel delay line comprise at least first and second switchable two-pixel delay elements.

Claim 16

The noise reduction filter as claimed in claim 11 wherein said switching means periodically switch connections to said tap points in a horizontal line oscillating pattern.

Claim 17

The noise reduction filter as claimed in claim 10 wherein said output terminal of the averaging circuit is coupled to said input terminal.

Claim 18

The noise reduction filter as claimed in claim 10 wherein said averaging circuit provides said filtered output video signal with filter weighting coefficients related to an absolute difference between a weighted pixel and the current input pixel.

Claim 19

A noise reduction filter comprising: delay means for furnishing a plurality of delayed signal samples (X); a weighted average filter coupled to a signal input terminal to receive a plurality of input signal samples (O,⊕) and to said delay means to receive said delayed signal samples (X) thereby to furnish noise-reduced signal samples to said delay means, wherein signal samples (Pn 1 . . . Pn n ) applied to said weighted average filter are not-directly neighboring samples, and means for assigning weighting coefficients to the samples (Pn 1 . . . Pn n ) of said input signal (O) and to said delayed signal (X) which depend on respective differences between a current sample (⊕,Pc) of said input signal and said samples (Pn 1 . . . Pn n ) of said input signal (O) and said delayed signal (X).

Claim 20

A noise reduction filter comprising: delay means for furnishing a plurality of delayed signal samples (X); a weighted average filter coupled to a signal input terminal to receive a plurality of input signal samples (O,⊕) and to said delay means to receive said delayed signal samples (X) thereby to furnish noise-reduced signal samples to said delay means, wherein signal samples (Pn 1 . . . Pn n ) applied to said weighted average filter are not-directly neighboring samples, and means for assigning weighting coefficients to the samples (Pn 1 . . . Pn n ) of said input signal (O) and to said delayed signal (X) which depend on respective differences between a current sample (⊕,Pc) of said input signal and said samples (Pn 1 . . . Pn n ) of said input signal (O) and said delayed signal (X).

Claim 21

A noise reduction filter as claimed in claim 1, wherein said filter comprises a weighted average filter in which weighting coefficients assigned to samples (Pn 1 . . . 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 and said samples (Pn 1 . . . Pn n ) of said input signal (O) and said delayed signal (X).

Claim 22

A luminance signal noise reduction filtering method comprising the steps of: supplying to a filter delayed signal samples wherein the positions of all said delayed signal samples from a previous line are line-alternatingly shifted in the horizontal direction on a line-by-line basis, supplying to the filter input luminance signal samples that are not directly neighboring samples, and filtering by means of said filter said input luminance signal samples and said delayed signal samples to furnish noise-reduced signal samples.

Claim 23

A luminance signal noise reduction filtering method comprising the steps of: supplying to a filter delayed signal samples wherein the positions of all said delayed signal samples from a previous line are line-alternatingly shifted in the horizontal direction on a line-by-line basis, supplying to the filter input luminance signal samples that are not directly neighboring samples, and filtering by means of said filter said input luminance signal samples and said delayed signal samples to furnish noise-reduced signal samples.

Claim 24

The noise reduction filter as claimed in claim 10 wherein said first tapped pixel delay line comprises a plurality of one-pixel delay elements interspersed with switchable two-pixel display elements, and the second tapped pixel delay line comprises switchable two-pixel delay elements.

Claim 25

A noise reduction filter comprising: an input terminal for receiving an input video signal made up of plural lines of signal samples, a filter having an input coupled to the signal input terminal to receive the input signal samples and having an output, delay means for deriving delayed signal samples and having an input coupled to the output of the filter and an output coupled to a further input of the filter to supply the delayed signal samples to the filter, and wherein all the signal samples received by the filter are not directly neighboring samples and said delayed samples are from a previous line and are taken from positions line-alternatingly shifted in the horizontal direction on a line-by-line basis, whereby a filtered output video signal with reduced noise is produced at the output of the filter.

Claim 26

A noise reduction filter comprising: an input terminal for receiving an input video signal made up of plural lines of signal samples, a filter having an input coupled to the signal input terminal to receive the input signal samples and having an output, delay means for deriving delayed signal samples and having an input coupled to the output of the filter and an output coupled to a further input of the filter to supply the delayed signal samples to the filter, and wherein all the signal samples received by the filter are not directly neighboring samples and said delayed samples are from a previous line and are taken from positions line-alternatingly shifted in the horizontal direction on a line-by-line basis, whereby a filtered output video signal with reduced noise is produced at the output of the filter.

Claim 27

The noise reduction filter as claimed in claim 21 wherein said delayed samples are horizontally shifted in an oscillating pattern.

Claim 28

The noise reduction filter as claimed in claim 1 wherein said delayed samples are horizontally shifted in an oscillating pattern.