Apparatus and method for filtering digital image signal
First Claim
Patent Images
1. An apparatus filtering a digital image signal, comprising:
- a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and
a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value,wherein the noise reduction filter comprisesa temporal filter which temporally filters the pixel values;
a spatial filter which spatially filters the pixel values; and
a filter selector which selectively outputs one of the results of the temporal and spatial filtering as the respective temporal or spatial filtering value in response to a result of a comparison between a local spatial mean value and each of the results of the temporal and spatial filtering, wherein the filter selector selects the temporal or spatial filtering value according to an Equation where “
{circumflex over (f)}s(,t)”
denotes the temporal or spatial filtering value, “
{circumflex over (f)}(,t)”
denotes the results of temporal filtering of the pixel values, “
f94(,t)”
denotes the results of spatial filtering of the pixel values, and “
f(,t)”
denotes the local spatial mean value.
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Abstract
An apparatus and method of filtering a digital image signal. The apparatus includes: a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each of frames of an image as a temporal or spatial filtering value in response to magnitudes of the results of temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the temporal or spatial filtering value.
43 Citations
18 Claims
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1. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the noise reduction filter comprises a temporal filter which temporally filters the pixel values; a spatial filter which spatially filters the pixel values; and a filter selector which selectively outputs one of the results of the temporal and spatial filtering as the respective temporal or spatial filtering value in response to a result of a comparison between a local spatial mean value and each of the results of the temporal and spatial filtering, wherein the filter selector selects the temporal or spatial filtering value according to an Equation where “
{circumflex over (f)}s(,t)”
denotes the temporal or spatial filtering value, “
{circumflex over (f)}(,t)”
denotes the results of temporal filtering of the pixel values, “
f94(,t)”
denotes the results of spatial filtering of the pixel values, and “
f (,t)”
denotes the local spatial mean value.
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2. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the noise reduction filter comprises a temporal filter which temporally filters the pixel values; a spatial filter which spatially filters the pixel values; and a filter selector which selectively outputs one of the results of the temporal and spatial filtering as the respective temporal or spatial filtering value in response to a result of a comparison between a local spatial mean value and each of the results of the temporal and spatial filtering wherein the temporal filter comprises a pixel value controller which compares a result of a subtraction of a pixel value of a previous frame from a pixel value of a current frame with a motion detection threshold value and outputs the comparison result as a pixel value control signal; a pixel value operator which generates a new pixel value using the pixel values of the previous and current frames; and a pixel value selector which selectively outputs the pixel value of the current frame or the new pixel value in response to the pixel value control signal. - View Dependent Claims (3)
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4. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the noise reduction filter comprises a temporal filter which temporally filters the pixel values; a spatial filter which spatially filters the pixel values; and a filter selector which selectively outputs one of the results of the temporal and spatial filtering as the respective temporal or spatial filtering value in response to a result of a comparison between a local spatial mean value and each of the results of the temporal and spatial filtering wherein the temporal filter comprises a pixel value controller which compares a result of a subtraction of a temporal or spatial filtering value of a previous frame from a pixel value of a current frame with a motion detection threshold value and outputs the comparison result as a pixel value control signal; a pixel value operator which adds a weight on the pixel value of the current frame and the temporal or spatial filtering value of the previous frame to generate at least one new pixel value; and a pixel value selector which selectively outputs the pixel value of the current frame or the at least one new pixel value in response to the pixel value control signal.
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5. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the noise reduction filter comprises a temporal filter which temporally filters the pixel values; a spatial filter which spatially filters the pixel values; and a filter selector which selectively outputs one of the results of the temporal and spatial filtering as the respective temporal or spatial filtering value in response to a result of a comparison between a local spatial mean value and each of the results of the temporal and spatial filtering wherein the temporal filter temporally filters the pixel values according to an Equation where, “
{circumflex over (f)}(,t)”
denotes the results of temporal filtering of the pixel values, “
f(,t)”
denotes the pixel value of a current frame, “
{circumflex over (f)}s(,t−
1)”
denotes the temporal or spatial filtering value of a previous frame, and d denotes a motion detection threshold value.
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6. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the noise reduction filter comprises a temporal filter which temporally filters the pixel values; a spatial filter which spatially filters the pixel values; and a filter selector which selectively outPuts one of the results of the temporal and spatial filtering as the respective temporal or spatial filtering value in response to a result of a comparison between a local spatial mean value and each of the results of the temporal and spatial filtering, wherein the spatial filter comprises a line delayer which receives the temporal or spatial filtering value generated for each neighboring pixel belonging to a previous line inside a window mask of predetermined size having a central pixel to delay the received temporal or spatial filtering value by a unit line; and a first multiplier which multiplies pixel values of the neighboring pixels belonging to the previous line input from the line delayer among pixels inside the window mask or pixel values of neighboring pixels belonging to a subsequent line input from an external source among pixels inside the window mask by corresponding weights, accumulates the multiplication results, and outputs the accumulation result as the result of spatial filtering of a pixel value of the central pixel, wherein the neighboring pixel neighbors the central pixel, and the previous and subsequent lines are respectively located before and after a current line to which the central pixel belongs. - View Dependent Claims (7, 8, 9, 10)
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11. An apparatus filtering a digital image signal, comprising
a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering: - and
a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value wherein the sharpness enhancement filter comprises a high pass component extractor which extracts a high pass component of the temporal or spatial filtering value for a central pixel; a gain determiner which determines a gain using a variation range of a difference between a pixel value of the central pixel and a pixel value of each neighboring pixel of the central pixel inside a filter mask; a second multiplier which multiplies the determined gain by the extracted high pass component; and a synthesizer which synthesizes the multiplication result of the second multiplier and the image and outputs the synthesis result as a sharpened result, wherein the neighboring pixels neighbor the central pixel, and the gain determiner determines the gain according to an Equation where th2, th3, and th4 denote second, third, and fourth predetermined threshold values, respectively, Drange denotes the variation range of the difference, Gain denotes the gain, and Gmax denotes a maximum value of the gain. - View Dependent Claims (12)
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13. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the sharpness enhancement filter comprises a high pass component extractor which extracts a high pass component of the temporal or spatial filtering value for a central pixel; a gain determiner which determines a gain using a variation range of a difference between a pixel value of the central pixel and a pixel value of each neighboring pixel of the central pixel inside a filter mask; a second multiplier which multiplies the determined gain by the extracted high pass component; and a synthesizer which synthesizes the multiplication result of the second multiplier and the image and outputs the synthesis result as a sharpened result, wherein the neighboring pixels neighbor the central pixel, and the high pass component extractor comprises a second pixel value difference calculator which calculates a pixel difference between the pixel value of the central pixel and the pixel value of each of the neighboring pixels; a parameter determiner which determines a parameter corresponding to a variation range of the difference calculated by the second pixel value difference calculator; a correlation calculator which calculates a correlation between the central pixel and the neighboring pixels using the parameter and the pixel difference; and a high pass component calculator which calculates the high pass component using the correlation and the temporal or spatial filtering value. - View Dependent Claims (14, 15, 16)
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17. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outPuts one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the sharpness enhancement filter comprises a high pass component extractor which extracts a high pass component of the temporal or spatial filtering value for a central pixel; a gain determiner which determines a gain using a variation range of a difference between a pixel value of the central pixel and a pixel value of each neighboring pixel of the central pixel inside a filter mask; a second multiplier which multiplies the determined gain by the extracted high pass component; and a synthesizer which synthesizes the multiplication result of the second multiplier and the image and outputs the synthesis result as a sharpened result, wherein the neighboring pixels neighbor the central pixel, the gain determiner comprises a gain adjuster which detects variation ranges of differences for all pixels belonging to a block having one of the neighboring pixels as a central pixel and adjusts the gain using the detected variation ranges of the differences, and the gain adjuster comprises a variation range detector which detects the variation range of the difference between the pixel value of each of the pixels belonging to the block and the pixel value of each of the neighboring pixels; a variation degree calculator which calculates a difference between maximum and minimum values of the variation range of the difference detected by the variation range detector; and a gain attenuator which adjusts the determined gain using the variation range of the difference in response to a magnitude of the difference calculated by the variation degree calculator.
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18. An apparatus filtering a digital image signal, comprising:
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a noise reduction filter which selectively outputs one of results obtained by temporally and spatially filtering pixel values of pixels of each frame of an image as a temporal or spatial filtering value in response to magnitudes of the results of the temporal and spatial filtering; and a sharpness enhancement filter which highlights and outputs a high pass component of the selected temporal or spatial filtering value, wherein the sharpness enhancement filter comprises a high pass component extractor which extracts a high pass component of the temporal or spatial filtering value for a central pixel; a gain determiner which determines a gain using a variation range of a difference between a pixel value of the central pixel and a pixel value of each neighboring pixel of the central pixel inside a filter mask; a second multiplier which multiplies the determined gain by the extracted high pass component; and a synthesizer which synthesizes the multiplication result of the second multiplier and the image and outputs the synthesis result as a sharpened result, wherein the neighboring pixels neighbor the central pixel, the gain determiner comprises a gain adjuster which detects variation ranges of differences for all pixels belonging to a block having one of the neighboring pixels as a central pixel and adjusts the gain using the detected variation ranges of the differences and when the difference calculated by the variation degree calculator is equal to or larger than a fifth predetermined threshold value, the gain attenuator adjusts the determined gain according to an Equation where Gfinal denotes the adjusted gain output from the gain attenuator, Gain denotes the determined gain, Drange denotes the variation range of the difference, and c denotes a number of the neighboring pixels.
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Specification