Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1995-12-12
2001-09-04
Lee, Richard (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S607000, C375S240180
Reexamination Certificate
active
06285710
ABSTRACT:
This application relates to noise reduction for video signal processing and compression apparatus, and more particularly to noise reduction apparatus for use within the video signal encoding loop.
BACKGROUND OF THE INVENTION
Predictive coding for compression of video signal functions best when current images are easily predicted from temporally adjacent images. However when the source images contain noise, accurate prediction becomes difficult and the compression efficiency declines or the reproduced image quality degrades or both. It is therefore desirable to minimize noise in the video signal to be compressed prior to the compression process.
Consider
FIG. 1
which illustrates a prior art predictive image coding system. Elements
12
-
22
form the actual predictive coder which will be described herein after. Noise reduction, in such prior art systems typically include a recursive noise reduction filter
10
to preprocess the video signal prior to compression. Field or frame recursive filters tend to have been preferred because they can effectively reduce noise components within the bandwidth of the active signal. However, such filters are also very memory intensive and require relatively sophisticated processing circuitry in order to perform significant noise reduction without introducing undesirable artifacts around moving image features
It is an object of the present invention to provide a highly effective noise filter apparatus and method for predictive encoders with minimal additional hardware.
SUMMARY OF THE INVENTION
The present invention reduces noise in video signal processing and compression. Video signal compression apparatus includes circuitry for generating residues representing pixel value differences between predicted and real pixel values of a current frame of a video signal. A nonlinear processor attenuates lower amplitude residues greater than higher amplitude residues and is responsive to a noise estimate. The processed residues are transformed to provide a compressed video data output.
In a feature of the invention, nonlinear processing functions are disclosed for noise estimation and for attenuation of noise and reduction of image distortion.
In another feature of the invention, noise estimation functions are disclosed.
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Composite Interframe Coding of NTSC Color Television Signals, by Ishiguro et al., 1976 IEEE National Telecommunications Convference vol. 1, pp. 6.4-1-6.4-5, Nov. 1976.*
A 64 Kbits/s Videophone Codec With Forward Analysis and Control, Signal Processing, Image Communication, vol. 2, No. 2 pp. 103-115, by Grotz et al., Oct. 1989.*
HDTV Coding at Below 45 Mbps for Digital Transmission, Globecom '91-IEEE Global Telecommunications conf. vol. 1/3, IEEE, pp. 96-100, by Chen et al., Dec. 1991.*
N. Hurst et al., In-Loop Coring: Robust MPEG Coding for Noisy Images, International Conference on Consumer Electronics—Digest of Technical Papers, Rosemont, IEEE Conf.14, Jun. 7, 1995, pp. 166-167.
Hurst, Jr. Robert Norman
Lee Jung-woo
Fogelson Joel M.
Kurdyla Ronald H.
Lee Richard
Thomson Licensing S.A.
Tripoli Joseph S.
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