US2013136376A1PendingUtilityA1
Image processing of video using noise estimate
Est. expiryMar 17, 2025(expired)· nominal 20-yr term from priority
Inventors:John Peter Oakley
G06K 9/40G06T 5/70H04N 25/63
38
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Cited by
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References
0
Claims
Abstract
A method of processing image date representing an image of a scene to generate an estimate of noise present in the image data. The method comprises evaluating a function for different values of the estimate, the function taking as input an estimate of the noise, and determining an estimate of the noise for which the function has an optimum value.
Claims
exact text as granted — not AI-modified1 . A method of processing a plurality of frames of video data to generate enhanced video data, comprising:
processing a first frame of video data to generate an estimate of noise included within said frame of video data; wherein said noise is at least partially attributable to atmospheric backscattered light; storing data indicative of said estimate of noise; processing at least one further frame of video data, which further frame indicates the same scene as said first frame of video data; to remove noise from said further frame of video data by subtracting said estimate of noise included in said first frame of video data and; outputting an enhanced frame of video data generated using said further frame of video data.
2 . A method according to claim 1 , wherein said subtracting comprises subtracting said estimate from values of said pixels of said video frame.
3 . A method according to claim 2 , further comprising rescaling values of said pixels after subtracting said estimate from values of said pixels.
4 . A method according to claim 1 , wherein processing at least one further frame of video data comprises processing a plurality of further frames of video data using said stored estimate of noise; and
the method comprises outputting a plurality of enhanced frames of video data.
5 . A method according to claim 1 , wherein said processing said first frame of video data to generate said estimate comprises:
evaluating a function for different values of said estimate, said function taking as input only an estimate of said noise; and determining an estimate of said noise for which said function has an optimum value.
6 . A method according to claim 5 , wherein first frame of video data comprises pixel values for each of a plurality of pixels of said frame, and said function takes as input as least a subset of said pixel values.
7 . A method according to claim 5 , further comprising:
filtering said video data to generate filtered video data comprising filtered pixel values; wherein said function takes as input at least a subset of said filtered pixel values.
8 . A method according to claim 5 , wherein said optimum value of said function is a stationary point of said function.
9 . A method according to claim 8 , wherein said stationary point is a minimum.
10 . A method according to claim 5 , wherein said function is of the form:
S
(
λ
)
=
1
K
∑
k
=
0
k
<
K
(
p
k
-
p
k
_
p
k
_
-
λ
)
2
·
exp
1
K
∑
k
=
0
k
<
K
(
ln
(
p
k
_
-
λ
)
2
)
where:
K is the number of pixels to be processed;
p k is the value of pixel k
p k is the value of pixel k after application of the lowpass filter described above;
λ is the value of the estimate; and
S(λ) is the function to be optimized.
11 . A method according to claim 5 , wherein said optimum value is determined using a numerical analysis technique.
12 . A method according to claim 10 , wherein said estimate is initially zero.
13 . A method according to claim 5 , comprising generating a plurality of estimates, each estimate being an estimate of noise in a respective subset of pixels of said video frame.
14 . A method according to claim 1 , wherein said step of processing at least one further frame comprises processing each pixel of said further video frame to remove said estimate of said noise to generate output pixel values.
15 . A method according to claim 14 , further comprising:
multiplying said output pixel values by a predetermined coefficient.
16 . A method according to claim 1 , wherein said noise is at least partially attributable to dirt on a camera lens.
17 . A method according to claim 1 , wherein said noise comprises an offset applied to at least a subset of pixels of said video frame, said offset being substantially equal for all pixels of said subset pixels of said video frame.
18 . A method according to claim 17 , wherein said offset is applied to all pixels of said video frame.
19 . A method according to claim 1 , wherein said noise comprises an offset applied to at least some pixels of said video frame, said offset being determined for particular independence upon a distance between a camera position used to generate said video frame, a point represented by that pixel.
20 . A method according to claim 1 , wherein said processing said first frame of video data further generates a contrast enhancement parameter.
21 . A computer apparatus for processing a plurality of frames of video data comprising:
a program memory containing processor readable instructions and; a processor configured to read and execute instructions stored in said program memory: wherein said processor readable instructions comprise instructions configured to cause the computer to carry out a method according to claim 1 .Join the waitlist — get patent alerts
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