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UBC Theses and Dissertations
Blocking artifacts removal of dicrete cosine transform based decompressed images Luo, Ying
Abstract
Block-based DCT image/video compression methods have been successfully used in image and video compression applications due to their nearly optimal energy compaction property and relative ease of implementation. However, compression distortion becomes significant when these algorithms are used to code images or video under a certain bit rate. The objective of this thesis is to offer post-processing solutions to reduce the block-based DCT image compression artifacts. The emphasis will be placed on the blocking artifacts since the blocking effect is one of the most noticeable degradations of block transform coding. We first analyze the causes and properties of the blocking effect. Then we propose a robust method which detects the locations of the image block boundaries where this effect occurs. The detection results using this method are proved to be accurate at different compression bit rates. Several practical blocking artifacts removal techniques are then reviewed and analyzed. The performance of each technique is studied and evaluated. Finally, a new blocking artifact reduction algorithm which is also effective at very low bit rate is proposed. Our algorithm takes advantage of the fact that the original pixel levels in the same block are of good continuity and we use this property and the correlation between the neighboring blocks to reduce the discontinuity of the pixels across the boundaries where blockiness appear. Our algorithm can highly preserve the high frequency components while smoothing out the boundary discontinuity. Simulation results show that the proposed algorithm significantly reduces the blocking artifacts in both the objective and the subjective measures. It can effectively remove blocking artifacts even at very low bit rates. The amount of computation it requires is also acceptable compared to the iterative blocking artifact removal techniques.
Item Metadata
Title |
Blocking artifacts removal of dicrete cosine transform based decompressed images
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1999
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Description |
Block-based DCT image/video compression methods have been successfully used in
image and video compression applications due to their nearly optimal energy compaction
property and relative ease of implementation. However, compression distortion becomes significant
when these algorithms are used to code images or video under a certain bit rate.
The objective of this thesis is to offer post-processing solutions to reduce the block-based
DCT image compression artifacts. The emphasis will be placed on the blocking artifacts since the
blocking effect is one of the most noticeable degradations of block transform coding.
We first analyze the causes and properties of the blocking effect. Then we propose a robust
method which detects the locations of the image block boundaries where this effect occurs. The
detection results using this method are proved to be accurate at different compression bit rates.
Several practical blocking artifacts removal techniques are then reviewed and analyzed. The
performance of each technique is studied and evaluated.
Finally, a new blocking artifact reduction algorithm which is also effective at very low bit
rate is proposed. Our algorithm takes advantage of the fact that the original pixel levels in the
same block are of good continuity and we use this property and the correlation between the
neighboring blocks to reduce the discontinuity of the pixels across the boundaries where blockiness
appear. Our algorithm can highly preserve the high frequency components while smoothing
out the boundary discontinuity. Simulation results show that the proposed algorithm significantly
reduces the blocking artifacts in both the objective and the subjective measures. It can effectively
remove blocking artifacts even at very low bit rates. The amount of computation it requires is also acceptable compared to the iterative blocking artifact removal techniques.
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Extent |
39675244 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-16
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0065337
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1999-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.