Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-07-08
2001-11-20
Lee, Young (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06320905
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
Invention relates to digital signal processing, particularly to electronic image post-processing of video signals to remove blocking artifacts in block-based signals.
2. Description of Background Art
Transform- and block-based coder-decoders or “codecs” are used for digital compression of still or video images (e.g., according to JPEG or MPEG industry standard data or signal format for digital image/video compression). However, when used at relatively low bit rates, such coders produce noticeable coding artifacts, such as blockiness and ringing. Both types of artifacts are undesirable and caused by attenuation of high frequency terms. With blockiness artifact, boundaries of coded blocks are visible in slow-varying regions in image or video frame. In comparison, with ringing artifact, sharp transitions or edges in image cause ringing effect in smooth areas of image. Blockiness is generally the more objectionable of the two artifacts. Although encoder modification may reduce blockiness, such approach would be unacceptable to extent modified encoder does not comply with applicable standards. Accordingly, there is need to reduce blocking artifact, particularly in MPEG-coded video streams, still-images, video conferencing applications, and other transformed-based codecs.
SUMMARY OF INVENTION
Digital video signal is de-blocked by processing vertical and/or horizontal neighboring edge pixels, particularly by applying thereto appropriate smoothing function (e.g., low-pass filter). Low-memory post-processor system neither requires DCT block characteristics nor blurs image edges close to block boundary.
REFERENCES:
patent: 5367385 (1994-11-01), Yuan
Hsia, S-C., Et Al., “Efficient Postprocessor for Blocky Effect Removal Based on Transform Characteristics”, IEEE Trans. on Circ. and Systems for Video Technology, vol. 7, No. 6, Dec. 1997, pp. 924-929.
Derviaux, C., Et Al., “A Postprocessing Technique for Block Effect Elimination Using a Perceptual Distortion Measure”, ICASSP-97, pp. 3001-3004.
Vasconcelos, N., Et Al. “Pre and Post-Filtering for Low Bit-Rate Video Coding,” ICIP 97.
Hu, J., Et Al., “Removal of Blocking and Ringing Artifacts in Transform Coded Images”, ICASSP-97, pp. 2565-2568.
Lynch, W. E., “Postprocessing Transform Coded Images Using Edges”, ICASSP-95, pp. 2323-2326.
Itu, ISO/IEC JTCI/SC29/WGII. MPEG4 Video Verfication Model Version 10.0, San Jose, CA. Feb. 1998.
Fernandez & Associates LLP
Lee Young
Stream Machine Company
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