Image analysis – Image compression or coding – Including details of decompression
Reexamination Certificate
1998-02-26
2001-10-02
Chang, Jon (Department: 2623)
Image analysis
Image compression or coding
Including details of decompression
C382S264000, C382S268000, C382S275000
Reexamination Certificate
active
06298161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a technique for decoding an image coded in accordance with an image coding method adopting the discrete cosine transform (DCT) standard, and more particularly to a digital image decoding apparatus and method that is adapted to suppress or reduce the discontinuity in image blocks, referred to as the blocking effect.
2. Description of the Prior Art
Data compression is required for handling large amounts of information resulting from the recent multimedia tendency in communication media. Accordingly, there have been developed various information compression techniques. The most typical example in these information compression techniques includes an image coding method proposed by the motion picture expert group (MPEG). This MPEG coding method codes image data to a type of bit stream and supplies the coded bit stream to storage media or communication media, thereby reducing a transfer rate of data, a band width of the communication media, a storage space of the storage media and so on.
In the MPEG coding method providing the above advantages, the DCT is used as a basic principle of information compression. This results from the DCT having a tendency of concentrating frequency characteristics irregularly distributed on the field into the low frequency region. Accordingly, the MPEG coding method performs an operation called “quantization”, in which the high frequency region is ignored after discrete cosine transforms, and thus is capable of reducing a loss of information to compress a picture efficiently. Further, in the MPEG coding method, the DCT is performed in a square block unit including a certain size of pixels, i.e., 8×8 pixels or 16×16 pixels, for one picture field. This DCT processing scheme acts as a factor that forces pixels in the boundaries of the square block to have discontinuous values in combination with the above-mentioned DCT characteristic of concentrating an information into the low frequency region. In other words, in the MPEG decoding method, there appears the discontinuity of image called “blocking effect” that makes a significant difference between values of pixels in the boundaries of a certain square block and those in the adjacent square blocks.
Image data compressed in accordance with the MPEG coding method adopting the DCT is decoded by means of a digital image decoding apparatus, as shown in
FIG. 1
, that includes a bit stream decoder
10
, a memory
12
and a display
14
. The bit stream decoder
10
performs the inverted quantization for a bit stream to derive high frequency components ignored upon coding and then performs the inverted discrete cosine transform (IDCT) of the inverted quantized data, thereby decoding the image data. The image data reconstructed by the bit stream decoder
10
pass through the memory
12
and is displayed on the display
14
.
However, square blocks divided into a constant size as shown in
FIG. 2
appear in the picture displayed by the digital image decoding apparatus as described above. This is caused by a fact that picture information concentrated in a mutually different frequency in a constant size of square block unit by the DCT upon MPEG coding is not reconstructed into its original form. This discontinuity of picture, that is, the blocking effect deteriorates a visuality of user and gives rise to “artifacts” in the boundaries of square blocks, thereby causing the user to feel an eye strain. For these reasons, the digital image decoding apparatus requires a function of suppressing or reducing the discontinuity of image or the blocking effects.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a digital image decoding apparatus and method that is capable of decoding the picture coded in accordance with the image coding method adopting the DCT standard.
In order to achieve the above and other objects of the invention, a digital image decoding apparatus according to an aspect of the present invention includes input means for receiving image data coded in accordance with a coding method adopting the discrete cosine transform (DCT), decoding means for performing the inverted discrete cosine transform (IDCT) for the coded image data from the input means to decode original image data, and filtering means for selectively filtering the decoded image data from the decoding means to eliminate blocking picture components.
A digital image decoding method according to another aspect of the present invention includes the steps of receiving image data coded in accordance with a coding method adopting the discrete cosine transform (DCT), performing the inverted discrete cosine transform (IDCT) for the coded image data to decode original image data, and selectively filtering the decoded image data to eliminate blocking picture components.
REFERENCES:
patent: 4754492 (1988-06-01), Malvar
patent: 5384849 (1995-01-01), Jeong
patent: 5539663 (1996-07-01), Agarwal
patent: 5555029 (1996-09-01), Kim
patent: 5590064 (1996-12-01), Astle
patent: 5694492 (1997-12-01), Kim
patent: 5734757 (1998-03-01), Kim
patent: 5852475 (1998-12-01), Gupta et al.
patent: 5926791 (1999-07-01), Ogata
patent: 5982459 (1999-11-01), Fandrianto et al.
patent: 6188799 (2001-02-01), Tan et al.
patent: 96-3420 (1996-01-01), None
patent: 96-39996 (1996-11-01), None
Huang. “Adaptive Filtering of Block Effects Based on Edge Map.” 3rd Int. Conf. on Signal Processing, 1996, Oct. 14, 1996, vol. pp. 583-586.
Lee et al. “Blocking Effect Reduction of JPEG Images by Signal Adaptive Filtering.” IEEE Transactions on Image Processing, vol. 7, No. 2, Feb. 1998, vol. 7, No. 2, pp. 229-234.
Lynch et al. “Post Processing Transform Coded Images Using Edges.” ICASSP-95, Int. Conf. on Acoustics, Speech and Signal Processing, May 9, 1995, vol. 4, pp. 2323-2326.
Kuo et al. “Adaptive Postprocessor for Block Encoded Images.” IEEE Transactions on Circuits and Systems for Video Technology, vol. 5, No. 4, Aug. 1995, pp. 298-304.
Koo Heon Mo
Lee Hee Sub
Min Cheol Hong
Chang Jon
Fleshner & Kim LLP
LG Electronics Inc.
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