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US 6,714,258 B2Granted
Video-apparatus with noise reduction
AssigneeKoninklijke Philips Electronics N.V.
InventorsJeroen Hubert Christoffel Jacobus Stessen, Gerard De Haan, Robert Jan Schutten, Fransiscus Wilhelmus Sijstermans
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Abstract
A video apparatus includes a circuit for reducing noise in applied input video signals. The noise reducing circuit is provided with a temporal noise filter (S1, LUT, M), a down-sample unit (D) for obtaining a spatial down-sampling of video signals (Vi) of subsequent pixels, these down-sampled video signals being supplied to the temporal noise filter (S1, LUT, M), and an up-sample unit (U) for generating, in response to noise output signals obtained in the temporal noise filter (S1, LUT, M), noise signals of the pixels, and a subtractor (S2) for subtracting the noise signals from the respective input video signals (Vi).
Claims12
A video noise reduction device comprising:
- a down-sample unit for spatially down-sampling input video signals to form down-sampled video signals;
- a temporal noise filter for filtering the down-sampled video signals to form noise output signals;
- an up-sample unit for generating noise signals in response to the noise output signals;
- and
- subtracting means for subtracting said noise signals from the respective input video signals to obtain noise-reduced video output signal,
- characterized in that said down-sample unit applies a quincunx down-sampling of video signals of pixels, whereby odd and even lines within a field have a phase difference corresponding with a down-sampling offset of half of the down-sampling ratio of the video signals.
3 more elements
A video noise reduction device comprising:
- a down-sample unit for spatially down-sampling input video signals to form down-sampled video signals;
- a temporal noise filter for filtering the down-sampled video signals to form noise output signals;
- an up-sample unit for generating noise signals in response to the noise output signals;
- and
- subtracting means for subtracting said noise signals from the respective input video signals to obtain noise-reduced video output signal,
- characterized in that the temporal noise filter is formed in such a way that a field or frame memory signal (So(m)) for a group of down-sampled video signals of subsequent pixels is a function of the last determined memory signals (So(m−1)) for said group of pixels and the down-sampled video input signal (Si(m)) from the down-sample unit substantially according to the relation:
- So(m)=Si(m)−(1−k)*[Si(m)−So(m−1)],
- where 1−k is a weight factor, depending on a difference signal (dif) formed by a difference between the signals (Si(m)) and (So(m−1)), the video-apparatus further comprising a look-up table (LUT) or a piecewise-linear function unit, said look-up table or said piecewise-linear function unit providing, in response to said difference signals (dif), a noise-representing output signal (No(m)=(1−k)*dif), for application to the up-sample unit.
5 more elements
A video noise reduction device comprising:
- a down-sample unit for spatially down-sampling input video signals to form down-sampled video signals;
- a temporal noise filter for filtering the down-sampled video signals to form noise output signals;
- an up-sample unit for generating noise signals in response to the noise output signals;
- and
- subtracting means for subtracting said noise signals from the respective input video signals to obtain noise-reduced video output siqnal,
- characterized in that the temporal noise filter is formed in such a way that a field or frame memory signal (So(m)) for a group of down-sampled video signals of subsequent pixels is a function of the last determined memory signals (So(m−1)) for said group of pixels and the down-sampled video input signal (Si(m)) from the down-sample unit (D) substantially according to the relation:
- So(m)=So(m−1)+k*[Si(m)−So(m−1)],
- where k is a weight factor, depending on a difference signal (dif) formed by a difference between the signals (Si(m)) and (So(m−1)), the video-apparatus further comprising a look-up table providing, in response to said difference signals (dif), a motion-representing output signal (k*dif), and a subtracting unit for subtracting the input and output signals of the look-up table to form a noise output signal (No(m)) for application to the up-sample unit, said noise output signal (No(m)) being represented by the relation:
- No(m)=(1−k)*dif.
6 more elements
A method of noise filtering comprising the steps:
- spatially down-sampling input video signals (Vi) to form down-sampled video signals;
- temporally noise filtering the down-sampled video signals to form noise output signals;
- up-sampling the noise output signals to generate noise signals, and subtracting said noise signals from the respective input video signals;
- characterized in that said down-sampling step applies a quincunx down-sampling of pixels of video signals, wherein odd and even lines within a field have a phase difference corresponding with a down-sampling offset of half of the down-sampling ratio of the video signals.
1 more element
A method of noise filtering comprising the steps:
- spatially down-sampling input video signals to form down-sampled video signals;
- temporally noise filtering the down-sampled video signals to form noise output signals;
- up-sampling the noise output signals to generate noise signals, and
- subtracting said noise signals from the respective input video signals,
- characterized in that the temporally noise filtering step is performed in such a way that a field or frame memory signal (So(m)) for a group of down-sampled video signals of subsequent pixels is a function of the last determined memory signals (So(m−1)) for said group of pixels and the down-sampled video input signal (Si(m)) from the down-sample unit substantially according to the relation:
- So(m)=Si(m)−(1−k)*[Si(m)−So(m−1)],
- where 1−k is a weight factor, depending on a difference signal (dif) formed by a difference between the signals (Si(m)) and (So(m−1)),
- the temporally noise filtering step further comprising:
- generating, in response to said difference signals (dif), a noise-representing output signal (No(m)=(1−k)*dif), for application to the up-sample unit.
6 more elements
A method of noise filtering comprising the steps:
- spatially down-sampling input video signals to form down-sampled video signals;
- temporally noise filtering the down-sampled video signals to form noise output signals;
- up-sampling the noise output signals to generate noise signals, and subtracting said noise signals from the respective input video signals,
- characterized in that the temporally noise filtering step is performed in such a way that a field or frame memory signal (So(m)) for a group of down-sampled video signals of subsequent pixels is a function of the last determined memory signals (So(m−1)) for said group of pixels and the down-sampled video input signal (Si(m)) from the down-sample unit substantially according to the relation:
- So(m)=So(m1)+k*[Si(m)−So(m−1)],
- where k is a weight factor, depending on a difference signal (dif) formed by a difference between the signals (Si(m)) and (So(m−1)), the temporally noise filtering step further comprising:
- generating a motion-representing output signal (k*diff) in response to said difference signals (dif);
- and
- subtracting said motion-representing output signal from said difference signal to form a noise-representing output signal (No(m)=(1−k)*dif), for application to the up-sample unit.
6 more elements
Dependencies are inferred from the claim text.