Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1997-06-27
2001-05-22
Rao, Andy (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240180
Reexamination Certificate
active
06236684
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for executing a wavelet transform on an image signal.
The wavelet transform is a mathematical tool for characterizing the local properties of a signal at a variety of resolutions. In recent years, this has been found to be an effective way to compress digitized image signals.
When the wavelet transform is applied to an image signal by the pyramid method of the prior art, which will be described in more detail later, the image signal passes in succession through a plurality of stages. In each stage, the signal is filtered horizontally and vertically, and the resolution of the signal is reduced by half in each dimension.
One problem with this method is the repeated need for temporary storage of the image signal. Signal storage is necessary between the horizontal filtering and vertical filtering operations in each stage of the transform, and is also necessary between the different stages. A filtering operation cannot begin until the signal has been stored, so besides consuming memory space, the repeated storage operations impair the speed of the transform.
Another problem is that in the final output signal of the transform, high and low spatial frequencies are mixed in a way that is not advantageous for compression. This problem will be described in more detail later.
A further problem is that the prior-art method works only with rectangular images. If an image is not rectangular, it must be embedded in a rectangle, and the non-image parts of the rectangle must be filled in with, for example, the average value of the image signal, or with signal values copied from the border of the image. Efficient compression of the resulting rectangular image tends to be impaired by high-frequency artifacts generated by the abrupt transitions between the image area and the filled-in area.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to execute a wavelet transform on a two-dimensional image signal without requiring a repeated storing of the image signal.
Another object of the present invention is to produce a wavelet transform output signal that can be highly compressed by further encoding.
Yet another object is to execute a wavelet transform on a two-dimensional image signal representing an image with an arbitrary shape, without generating artifacts.
According to a first aspect of the invention, an N-level wavelet transform is executed on an image signal, where N is an integer greater than one. The image signal represents an image having a first dimension and a second dimension. First, an N-level one-dimensional wavelet transform is executed on the image signal in the first dimension, generating an intermediate signal which is temporarily stored in a memory device. Then an N-level one-dimensional thereby wavelet transform is executed on the intermediate signal in the second dimension. Each N-level one-dimensional wavelet transform is preferably executed by a single matrix operation.
According to a second aspect of the invention, an N-level wavelet transform is executed on an image signal, where N is an integer greater than zero. The image signal represents an image having a first dimension and a second dimension, and having an arbitrary shape. The image signal is accompanied by shape information describing the shape of the image. First, N single-level one-dimensional wavelet transforms are executed on the image signal in a cascaded series in the first dimension, thereby generating an intermediate signal which is temporarily stored in a memory device. When each single-level one-dimensional wavelet transform is executed, the shape information is altered to describe the shapes of the component signals resulting from the transform. Next, N single-level one-dimensional wavelet transforms are executed on the intermediate signal in a cascaded series in the second dimension, accompanied by further similar alterations of the shape information.
REFERENCES:
patent: 5347479 (1994-09-01), Miyazaki
patent: 5563960 (1996-10-01), Shapiro
patent: 5602589 (1997-02-01), Vishwanath et al.
patent: 5657085 (1997-08-01), Katto
patent: 5710835 (1998-01-01), Bradley
patent: 5757974 (1998-05-01), Impagliazzo et al.
patent: 5764807 (1998-06-01), Pearlman et al.
patent: 5777678 (1998-07-01), Ogata et al.
patent: 5819215 (1998-10-01), Dobson et al.
patent: 5825935 (1998-10-01), Murakoshi
patent: 5828849 (1998-10-01), Lempel et al.
patent: 5838377 (1998-11-01), Greene
patent: 5852681 (1998-12-01), Amaratunga et al.
patent: 5867221 (1999-02-01), Pullen et al.
patent: 5867602 (1999-02-01), Zandi et al.
patent: 5946417 (1999-08-01), Bonneau et al.
Mallet, “A Theory for Multiresolution Signal Decomposition: The Wavelet Representation”, IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 11, No. 7, Jul. 1989, pp. 674-693.
Egger O et al.: “Arbitrarily-Shaped Wavelet Packets for Zerotree Coding” 1996 IEEE International Conference on Acoustics, Speech, and Signal Processing—Proceedings. (ICASSP), Atlanta, May 7-10. 1996, vol. 4, No. Conf. 21, May 7, 1996, pp. 2335-2338, XP000681695 Institute of Electrical and Electronics Engineers.
Parhi K K et al.: “VLSI Architectures for Discrete Wavelet Transforms” IEEE Transactions on Very Large Scale Integration (VLSI) Systems, vol. 1, No. 2, Jun. 1, 1993, pp. 191-202, XP000390612.
OKI Electric Industry Co., Ltd.
Rao Andy
Wenderoth , Lind & Ponack, L.L.P.
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