US6281942B1
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US
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Spatial and temporal filtering mechanism for digital motion video signals
Assignee: Microsoft Technology Licensing LLC
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Filing: 1997-08-11
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Granted: 2001-08-28
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Expires: 2017-08-11
Abstract
Abstract Frames of a digital video signal are spatially filtered to remove impulse and other noise from the video signal. The spatially filtered frame is temporally filtered to further remove noise from the digital video signal. The spatial filter is adaptive, heavily filtering portions of low detail in the represented subject matter while lightly filtering or not filtering portions of moderate to high detail in the represented subject matter. As a result, clarity and detail in the subject matter of the digital video signal are preserved. The temporal filter is similarly adaptive and determines if and to what degree the subject matter of portions of the spatially filtered frame correlate with corresponding portions of a previous frame. By previously spatially filtering the frame, determinations regarding the correlation of the current frame with corresponding portions of the previous, which is also spatially and temporally filtered, are more accurate. Accordingly, temporal filtering can be performed more aggressively without temporally blurring the digital video signal. The result of spatial and temporal filtering of the digital video signal is significant reduction in noise without degradation of the signal and improved compression of the digital video signal.
Inventors
- 👤 Albert S. Wang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 18:41
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/21; H04N5/213; H04N19/00; H04N19/10; H04N19/102; H04N19/117; H04N19/124; H04N19/132; H04N19/134; H04N19/136; H04N19/14; H04N19/169; H04N19/17; H04N19/176; H04N19/182; H04N19/50; H04N19/587; H04N19/60; H04N19/61; H04N19/80; H04N21/00; H04N21/20; H04N21/23; H04N21/234; H04N21/2343; H04N21/234354; H04N21/234381; H04N21/40; H04N21/41; H04N21/426
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
179 words
A method for filtering at least a portion of a digital video signal, the method comprising: calculating a pixel variance for a block of source pixels from a current frame of the motion video image; applying a heavy spatial filter to the block of source pixels to form a block of spatially filtered pixels representing current subject matter of the current frame when the pixel variance is less than a first pixel variance threshold; applying a light spatial filter to the block of source pixels to form the block of spatially filtered pixels when the pixel variance is less than a second pixel variance threshold; calculating a pixel error between the block of spatially filtered pixels and a block of pixels of a previous frame of the digital video signal; applying a heavy temporal filter to the block of spatially filtered pixels when the pixel error is less than a first pixel error threshold; and applying a light temporal filter to the block of spatially filtered pixels when the pixel error is less than a second pixel error threshold.
Claim 2
Independent Claim
179 words
A method for filtering at least a portion of a digital video signal, the method comprising: calculating a pixel variance for a block of source pixels from a current frame of the motion video image; applying a heavy spatial filter to the block of source pixels to form a block of spatially filtered pixels representing current subject matter of the current frame when the pixel variance is less than a first pixel variance threshold; applying a light spatial filter to the block of source pixels to form the block of spatially filtered pixels when the pixel variance is less than a second pixel variance threshold; calculating a pixel error between the block of spatially filtered pixels and a block of pixels of a previous frame of the digital video signal; applying a heavy temporal filter to the block of spatially filtered pixels when the pixel error is less than a first pixel error threshold; and applying a light temporal filter to the block of spatially filtered pixels when the pixel error is less than a second pixel error threshold.
Claim 3
Dependent Claim
63 words
The method of claim 1 wherein the step of applying a light spatial filter comprises applying a five pixel median filter and a five pixel smoothing filter to the block of source pixels, and further wherein the step of applying a heavy spatial filter comprises applying a five pixel median filter and a nine pixel smoothing filter to the block of source pixels.
Claim 4
Dependent Claim
15 words
The method of claim 1 wherein the calculated pixel error is an absolute pixel difference.
Claim 5
Dependent Claim
205 words
A computer readable medium useful in association with a computer which includes a processor and a memory, the computer readable medium including computer instructions which are configured to cause the computer to filter a digital video signal by performing the steps of: calculating a pixel variance for a block of source pixels from a current frame of the motion video image; applying a heavy spatial filter to the block of source pixels to form a block of spatially filtered pixels representing current subject matter of the current frame when the pixel variance is less than a first pixel variance threshold; applying a light spatial filter to the block of source pixels to form the block of spatially filtered pixels when the pixel variance is less than a second pixel variance threshold; calculating a pixel error between the block of spatially filtered pixels and a block of pixels of a previous frame of the digital video signal; applying a heavy temporal filter to the block of spatially filtered pixels when the pixel error is less than a first pixel error threshold; and applying a light temporal filter to the block of spatially filtered pixels when the pixel error is less than a second pixel error threshold.
Claim 6
Dependent Claim
205 words
A computer readable medium useful in association with a computer which includes a processor and a memory, the computer readable medium including computer instructions which are configured to cause the computer to filter a digital video signal by performing the steps of: calculating a pixel variance for a block of source pixels from a current frame of the motion video image; applying a heavy spatial filter to the block of source pixels to form a block of spatially filtered pixels representing current subject matter of the current frame when the pixel variance is less than a first pixel variance threshold; applying a light spatial filter to the block of source pixels to form the block of spatially filtered pixels when the pixel variance is less than a second pixel variance threshold; calculating a pixel error between the block of spatially filtered pixels and a block of pixels of a previous frame of the digital video signal; applying a heavy temporal filter to the block of spatially filtered pixels when the pixel error is less than a first pixel error threshold; and applying a light temporal filter to the block of spatially filtered pixels when the pixel error is less than a second pixel error threshold.
Claim 7
Dependent Claim
65 words
The computer readable medium of claim 4 wherein the step of applying a light spatial filter comprises applying a five pixel median filter and a five pixel smoothing filter to the block of source pixels, and further wherein the step of applying a heavy spatial filter comprises applying a five pixel median filter and a nine pixel smoothing filter to the block of source pixels.
Claim 8
Dependent Claim
17 words
The computer readable medium of claim 4 wherein the calculated pixel error is an absolute pixel difference.
Claim 9
Dependent Claim
212 words
A computer system comprising: a processor, a memory operatively coupled to the processor; and a digital video signal filter which executes in the processor from the memory and which, when executed by the processor, causes the computer to filter a digital video signal by performing the steps of: calculating a pixel variance for a block of source pixels from a current frame of the motion video image; applying a heavy spatial filter to the block of source pixels to form a block of spatially filtered pixels representing current subject matter of the current frame when the pixel variance is less than a first pixel variance threshold; applying a light spatial filter to the block of source of pixels to form the block of spatially filtered pixels when the pixel variance is less than a second pixel variance threshold; calculating a pixel error between the block of spatially filtered pixels and a block of pixels of a previous frame of the digital video signal; applying a heavy temporal filter to the block of spatially filtered pixels when the pixel error is less than a first pixel error threshold; and applying a light temporal filter to the block of spatially filtered pixels when the pixel error is less than a second pixel error threshold.
Claim 10
Dependent Claim
212 words
A computer system comprising: a processor, a memory operatively coupled to the processor; and a digital video signal filter which executes in the processor from the memory and which, when executed by the processor, causes the computer to filter a digital video signal by performing the steps of: calculating a pixel variance for a block of source pixels from a current frame of the motion video image; applying a heavy spatial filter to the block of source pixels to form a block of spatially filtered pixels representing current subject matter of the current frame when the pixel variance is less than a first pixel variance threshold; applying a light spatial filter to the block of source of pixels to form the block of spatially filtered pixels when the pixel variance is less than a second pixel variance threshold; calculating a pixel error between the block of spatially filtered pixels and a block of pixels of a previous frame of the digital video signal; applying a heavy temporal filter to the block of spatially filtered pixels when the pixel error is less than a first pixel error threshold; and applying a light temporal filter to the block of spatially filtered pixels when the pixel error is less than a second pixel error threshold.
Claim 11
Dependent Claim
64 words
The computer system of claim 7 wherein the step of applying a light spatial filter comprises applying a five pixel median filter and a five pixel smoothing filter to the block of source pixels, and further wherein the step of applying a heavy spatial filter comprises applying a five pixel median filter and a nine pixel smoothing filter to the block of source pixels.
Claim 12
Dependent Claim
16 words
The computer system of claim 7 wherein the calculated pixel error is an absolute pixel difference.
Claim 13
Dependent Claim
57 words
The computer system of claim 7 wherein the step of comparing comprises: measuring a difference between the block of spatially filtered pixels and the block of pixels of the previous frame; and determining whether the block of pixels of the previous frame represents the current subject matter by comparison of the measured difference to a predetermined threshold.
Claim 14
Dependent Claim
78 words
The method of claim 1 , wherein the step of applying a heavy temporal filter includes applying a two-tap infinite impulse response filter in which the pixels of the previous frame are weighted by a factor of substantially equal to 0.75, and further wherein the step of applying a light temporal filter includes applying a two-tap infinite impulse response filter in which the pixels of the previous frame are weighted by a factor of substantially equal to 0.5.
Claim 15
Dependent Claim
80 words
The computer readable medium of claim 4 , wherein the step of applying a heavy temporal filter includes applying a two-tap infinite impulse response filter in which the pixels of the previous frame are weighted by a factor of substantially equal to 0.75, and further wherein the step of applying a light temporal filter includes applying a two-tap infinite impulse response filter in which the pixels of the previous frame are weighted by a factor of substantially equal to 0.5.
Claim 16
Dependent Claim
79 words
The computer system of claim 7 , wherein the step of applying a heavy temporal filter includes applying a two-tap infinite impulse response filter in which the pixels of the previous frame are weighted by a factor of substantially equal to 0.75, and further wherein the step of applying a light temporal filter includes applying a two-tap infinite impulse response filter in which the pixels of the previous frame are weighted by a factor of substantially equal to 0.5.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-08-27 | 2005-02-26 | 2005-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-08-27 | 2009-02-26 | 2009-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-08-27 | 2013-02-26 | 2013-08-28 | $7700.00 | Window Closed / Lapsed |