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The explicit four-tap Daubechies pair satisfies the orthogonal filter and two-moment conditions
Statement
The pair in Explicit four-tap Daubechies filter and its high-pass partner is admissible in Periodic finite orthogonal compact-filter wavelet transform. In addition, for , so the high-pass filter annihilates constant and affine data.
Facts & Assumptions
Given: The exact four entries of and the definition .
Periodic finite orthogonal compact-filter wavelet transform: admissibility requires unit even-shift autocorrelation for each filter, zero cross-correlation at every even shift, , and .
Proof
Write . Direct addition gives . The numerator of is , and the numerator of is . Thus has the required zero sum and two vanishing moments.
With denominator , the numerator of is , so the zero-shift autocorrelation is . The only possible nonzero even-shift autocorrelation of a four-tap filter is at shift or ; at shift its numerator is , and the shift sum is the same by reindexing. Reversal with alternating signs gives and .
For the cross-correlation , only can have overlapping taps. These sums are respectively , by pairwise cancellation, and . For all other integers the supports do not overlap, so the sum is zero. Together with steps 1.1 and 1.2 this verifies every condition in [F2].
Depends on
Used by
- Periodic multilevel transform using the four-tap Daubechies filter Definition
- Local support, affine cancellation, and normalization of multilevel D4 detail rows Lemma
Cited to discharge well-definedness by Explicit four-tap Daubechies filter and its high-pass partner.
Dependency tree · two levels
3 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Gilbert Strang and Kevin Amaratunga, Wavelets and Filter Banks, MIT OpenCourseWare 18.327, Handout 8 (standard reference, not scraped)
- Jelena Kovačević, Vivek K. Goyal, and Martin Vetterli, Fourier and Wavelet Signal Processing (standard reference, not scraped)