| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Wavelet-based image coding has been extensively studied and adopted in the international standard JPEG2000. In the wavelet-based image coding, two-band PR (perfect reconstruction) filter banks play a very important role. The analysis and synthesis filters are required to have exactly linear phase responses (corresponding to symmetric wavelet bases), allowing us to use the symmetric extension method to accurately handle the boundaries of images. The wavelet filter banks should also be orthonormal to avoid redundancy between the subband images. Unfortunately, there are no nontrivial orthonormal symmetric wavelets with FIR filters, except for the Haar wavelet. To achieve better compression performance, a reasonable regularity is necessary for wavelet bases. Therefore, at least one of the above-mentioned conditions has to be given up to get more regularity than the Haar wavelet. For example, the D-9/7 and D-5/3 wavelets supported by the baseline codec of JPEG2000 are biorthogonal. On the other hand, it is known that IIR, wavelet filters can simultaneously satisfy both of the orthonormality and symmetry. A class of IIR orthonormal symmetric wavelets has been proposed by using allpass filters.
We apply the allpass-based orthonormal symmetric wavelets to image compression, and propose an effective implementation of the wavelet filter banks. Firstly, we present the implementation of irreversible real-to-real wavelets and show its decomposition process by using allpass filters. Then, we make use of the invertible implementation of allpass filters to realize the reversible integer-to-integer wavelets. Finally, we investigate the coding performance of the allpass-based orthonormal symmetric wavelets by using the reference software of JPEG2000, and compare the performance with the D-9/7 and D-5/3 wavelets. It is shown from the experimental results that the allpass-based orthonormal symmetric wavelets can achieve better compression performance than the D-9/7 and D-5/3 wavelets.
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