A method and apparatus to remove a block effect and a ring effect appearing in a compression-coded image is disclosed. The present invention is especially applicable to an image compression-coded at a low bit rate. In particular, the present invention includes a variety of masks for the removal of the block/ring effect. Thus, one mask is select for a pixel to be filtered. Moreover, candidate pixels to be averaged with the pixel to be filtered is selected from the pixels of the selected mask to better maintain the details of the image, and a weight is applied to improve the calculation speed of the averaging operation. More particularly, the masks according to the present invention have longer tabs toward adjacent blocks at boundaries of the given block to remove the block and ring effect. In the method, a pixel of an image is filtered according to a filtering methodology. The filtering methodology includes selecting at least four pixels of successive pixels according to a position of a pixel to be filtered. The four pixels include the pixel to be filtered. At least one of the four pixels may be in a first block, and three of the four pixels may be in a second block adjacent to the first block. The filtering methodology includes determining a difference between two of the successive pixels and comparing the difference to a threshold.

Patent
   RE41459
Priority
Aug 31 1998
Filed
Apr 13 2007
Issued
Jul 27 2010
Expiry
Jul 15 2023

TERM.DISCL.
Assg.orig
Entity
Large
0
64
EXPIRED
0. 21. A method of filtering an image, comprising:
filtering, with a filtering unit, a pixel of an image according to a filtering methodology, the filtering methodology including,
selecting at least four pixels of successive pixels according to a position of a pixel to be filtered, the selected at least four pixels including the pixel to be filtered, at least one of the selected at least four pixels being in a first block, and three of the selected at least four pixels being in a second block adjacent to the first block,
determining a difference between two of the selected at least four successive pixels, the two of the selected at least four pixels including non-adjacent pixels, and
comparing the difference to a threshold.
0. 1. A filtering method for a pixel P of a block B in a reconstructed image, comprising:
selecting one of a plurality of filtering masks based upon a position of said pixel P in said block B; and
averaging said pixel P and candidate pixels within the selected filtering mask.
0. 2. A method of claim 1, wherein each of the plurality of filtering masks has 8 tabs.
0. 3. A method of claim 1, wherein a filtering mask with more tabs toward a block adjacent said block B is selected.
0. 4. A method of claim 1, further comprising selecting a pixel within the selected filtering mask Pm as a candidate pixel if the value of the pixel Pm meets a predetermined condition.
0. 5. A method of claim 4, wherein the pixel Pm is selected as a candidate pixel if the absolute value of the difference between said pixel P and pixel Pm is less than a threshold value.
0. 6. A method of claim 5, wherein the threshold value is calculated by an equation below,

δ=k×q
where k is a constant and q is a quantization step interval of said block B.
0. 7. A method of claim 6, wherein the value of k is 1.0 for filtering boundary pixels of said block B and 0.6 for filtering pixels within the boundary pixels of said block B.
0. 8. A method of claim 4, further comprising adding a weight value to said pixel P prior to the averaging, wherein said weight value is based upon a number of pixels Pm not selected as candidate pixels.
0. 9. A method of claim 8, wherein said weight value is the number of pixels Pm not selected multiplied by the value of said pixel P.
0. 10. A filtering apparatus to filter a pixel P of a block B in a reconstructed image, comprising:
a filtering masking unit selecting one of a plurality filtering masks based upon a position of said pixel P in said block B; and
an averaging unit averaging said pixel P and candidate pixels within the selected mask.
0. 11. An apparatus of claim 10, wherein each of the plurality of filtering masks has 8 tabs.
0. 12. An apparatus of claim 11, wherein the plurality of filtereing masks are modified 3×3 mask forms including:
a filtering mask in which eight tabs are selected from the 3×3 mask form, discarding one corner tab;
a filtering mask in which more tabs are selected in a vertical direction than a horizontal direction, and more vertical lower tabs are selected than vertical upper tabs;
a filtering mask in which more tabs are selected in the vertical direction than the horizontal direction, and more vertical upper tabs are selected than vertical lower tabs;
a filtering mask in which more tabs are selected in the horizontal direction than the vertical direction, and more horizontal left tabs are selected than horizontal right tabs; and
a filtering mask in which more tabs are selected in the horizontal direction than the vertical direction, and more horizontal right tabs are selected than horizontal left tabs.
0. 13. An apparatus of claim 10, wherein a filtering mask with more tabs toward a block adjacent said block B is selected.
0. 14. An apparatus of claim 10, further comprising:
a comparison unit selecting a pixel within the selected mask Pm as a candidate pixel if the value of the pixel Pm meets a predetermined condition.
0. 15. An apparatus of claim 14, wherein the pixel Pm is selected as a candidate pixel if the absolute value of the difference between said pixel P and pixel Pm is less than a threshold value.
0. 16. An apparatus of claim 15, wherein the threshold value is calculated by an equation below,

δ=k×q
where k is a constant and q is a quantization step interval of said block B.
0. 17. An apparatus of claim 16, wherein the value of k is 1.0 for filtering boundary pixels of said block B and 0.6 for filtering pixels within the boundary pixels of said block.
0. 18. An apparatus of claim 14, wherein the averaging unit adds a weight value to said pixel P prior to the averaging, wherein said weight value is based upon a number of pixels Pm not selected as candidate pixels.
0. 19. An apparatus of claim 18, wherein said weight value is the number of pixels Pm not selected multiplied by the value of said pixel P.
0. 20. A coding and decoding method comprising:
a discrete cosine transform (DCT) unit performing a DCT operation with respect to divided blocks of an image to generate DCT coefficients;
a quantization unit quantizing the DCT coefficients and transmitting the DCT coefficients in a form of a bit stream through a transmission channel;
a dequantization unit dequantizing the DCT coefficients received through the transmission channel;
an inverse DCT unit performing an inverse DCT operation with respect to the dequantized DCT coefficients to form a reconstructed image, and
a filtering process unit filtering each pixel of each block of the reconstructed image by selecting one of a plurality of filtering masks based upon a position of said pixel in said block; and averaging said pixel and candidate pixels within the selected filtering mask.
0. 22. The method of claim 21, wherein the difference is between two of the selected at least four pixels in the second block.
0. 23. The method of claim 22, wherein one of the two selected pixels upon which the difference is based is the pixel to be filtered.
0. 24. The method of claim 22, wherein the difference is based on the pixel to be filtered and a nearby pixel.
0. 25. The method of claim 21, wherein one of the two selected pixels upon which the difference is based is the pixel to be filtered.
0. 26. The method of claim 25, wherein the pixel to be filtered is in the first block.
0. 27. The method of claim 26, wherein one of the two successive pixels upon which the difference is based is in the second block.
0. 28. The method of claim 21, wherein the filtering methodology includes determining the difference between a pixel in the first block and a nearby one of the pixels in the second block.
0. 29. The method of claim 28, wherein the pixel in the first block is the pixel to be filtered.
0. 30. The method of claim 28, wherein one of the pixels in the second block is the pixel to be filtered.

predetermined
where, k is a constant and q is the quantization step interval of a block.

In claims invention. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

Kim, Jae Min

Patent Priority Assignee Title
Patent Priority Assignee Title
5122875, Feb 27 1991 GENERAL ELECTRIC COMPANY, A CORP OF NY An HDTV compression system
5283646, Apr 09 1992 Polycom, Inc Quantizer control method and apparatus
5367385, May 07 1992 Polycom, Inc Method and apparatus for processing block coded image data to reduce boundary artifacts between adjacent image blocks
5488570, Nov 24 1993 Intel Corporation Encoding and decoding video signals using adaptive filter switching criteria
5555028, Jun 30 1994 QUARTERHILL INC ; WI-LAN INC Post-processing method and apparatus for use in an image signal decoding system
5563813, Jun 01 1994 Industrial Technology Research Institute Area/time-efficient motion estimation micro core
5611000, Feb 22 1994 HEWLETT-PACKARD DEVELOPMENT COMPANY, L P Spline-based image registration
5694492, Apr 30 1994 Daewoo Electronics Co., Ltd Post-processing method and apparatus for removing a blocking effect in a decoded image signal
5748795, Feb 07 1995 Canon Kabushiki Kaisha Image decoder using adjustable filtering
5748799, Sep 29 1995 FUJIFILM Corporation Image processing method and apparatus
5787210, Oct 31 1994 ZTE Corporation Post-processing method for use in an image signal decoding system
5790131, May 15 1996 HEWLETT-PACKARD DEVELOPMENT COMPANY, L P System and method for lossy compression of data with output file size control
5877813, Jul 06 1996 SAMSUNG ELECTRONICS CO , LTD Loop filtering method for reducing blocking effects and ringing noise of a motion-compensated image
5878166, Dec 26 1995 AVAGO TECHNOLOGIES GENERAL IP SINGAPORE PTE LTD Field frame macroblock encoding decision
5883983, Mar 23 1996 Qualcomm Incorporated Adaptive postprocessing system for reducing blocking effects and ringing noise in decompressed image signals
5933541, Aug 17 1995 Siemens Aktiengesellschaft Method for processing decoded picture blocks in a block-based method of picture coding
5937101, Jan 20 1995 SAMSUNG ELECTRICS CO , LTD Post-processing device for eliminating blocking artifact and method therefor
5940536, Sep 05 1995 Matsushita Electric Industrial Co., Ltd. Ringing detector and filter
5970179, Aug 16 1996 FUJIFILM Corporation Method of and apparatus for filtering image
5974196, Mar 15 1996 Sony Corporation; Sony Electronics, Inc.; Sony Electronics, INC Method and apparatus for blocking effect reduction in images
5974197, Jan 29 1997 SAMSUNG ELECTRONICS CO , LTD Loop filter and loop filtering method
6041145, Nov 02 1995 MATSUSHITA ELECTRIC INDUSTRIAL CO , LTD Device and method for smoothing picture signal, device and method for encoding picture and device and method for decoding picture
6058210, Sep 15 1997 Xerox Corporation Using encoding cost data for segmentation of compressed image sequences
6108455, May 29 1998 STMicroelectronics, Inc. Non-linear image filter for filtering noise
6167164, Mar 10 1997 SAMSUNG ELECTRONICS CO , LTD One-dimensional signal adaptive filter for reducing blocking effect and filtering method
6178205, Dec 12 1997 Cisco Technology, Inc Video postfiltering with motion-compensated temporal filtering and/or spatial-adaptive filtering
6188799, Feb 07 1997 MATSUSHITA ELECTRIC INDUSTRIES CO LTD Method and apparatus for removing noise in still and moving pictures
6192081, Oct 26 1995 MEDIATEK, INC Apparatus and method for selecting a coding mode in a block-based coding system
6195632, Nov 25 1998 Panasonic Intellectual Property Corporation of America Extracting formant-based source-filter data for coding and synthesis employing cost function and inverse filtering
6222641, Jul 01 1998 Electronics for Imaging, Inc. Method and apparatus for image descreening
6226050, Apr 04 1997 SAMSUNG ELECTRONICS CO , LTD Signal adaptive filtering method for reducing ringing noise and signal adaptive filter
6246802, Sep 30 1996 NEC PERSONAL COMPUTERS, LTD Image data processor
6259823, Feb 15 1997 SAMSUNG ELECTRONICS CO,, LTD Signal adaptive filtering method and signal adaptive filter for reducing blocking effect and ringing noise
6320987, Oct 16 1998 VICHIP CORPORATION, LTD Pre-DCT residue filter
6360014, Sep 26 1997 MATSUSHITA ELECTRIC INDUSTRIAL CO , LTD Image decoding method, image decoding apparatus, and data recording medium
6360024, Feb 07 1997 Matsushita Electric Industrial Co., Ltd. Method and apparatus for removing noise in still and moving pictures
6381275, Jun 28 1996 Mitsubishi Denki Kabushiki Kaisha Image coding apparatus and image decoding apparatus
6385245, Sep 23 1997 NXP B V Motion estimation and motion-compensated interpolition
6415055, Dec 12 1994 Sony Corporation Moving image encoding method and apparatus, and moving image decoding method and apparatus
6463182, Dec 28 1995 Canon Kabushiki Kaisha Image processing apparatus and method for removing noise near an edge of an image
6504873, Jun 13 1997 Nokia Technologies Oy Filtering based on activities inside the video blocks and at their boundary
6529638, Feb 01 1999 RAKUTEN, INC Block boundary artifact reduction for block-based image compression
6535643, Nov 03 1998 LG Electronics Inc. Method for recovering compressed motion picture for eliminating blocking artifacts and ring effects and apparatus therefor
6594400, Aug 31 1998 LG Electronics Inc. Method of removing block phenomenon and ring phenomenon in compression coded image
6631162, Jul 16 1997 SAMSUNG ELECTRONICS CO , LTD Signal adaptive filtering method, signal adaptive filter and computer readable medium for storing program therefor
6665346, Aug 01 1998 SAMSUNG ELECTRONICS CO , LTD ; Korea Advanced Institute of Science and Technology Loop-filtering method for image data and apparatus therefor
7054503, Feb 23 2001 Godo Kaisha IP Bridge 1 Image processing system, image processing method, and image processing program
7162090, Mar 07 2002 Seiko Epson Corporation Image processing apparatus, image processing program and image processing method
7215823, Jul 24 2001 Seiko Epson Corporation Deblocking and deringing apparatus, program and method
7302104, Dec 28 2001 Ricoh Co., Ltd. Smoothing tile boundaries of images encoded and decoded by JPEG 2000
7305142, Jul 30 1997 LG Electronics Inc Method of reducing a blocking artifact when coding moving picture
20030044080,
20040179610,
20050147319,
20050196066,
20050201633,
20060078055,
20070140574,
20070258657,
20070292042,
20070292043,
JP1070719,
JP9326024,
WO9904497,
/
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