access icon free Appendix E: Introduction to wavelet theory

At first sight, wavelet transformation seems to combine several advantages of sub-band coding and conventional FFT or DCT while being computationally more efficient. The continuous nature of the transform, as opposed to DCT blocks, helps to avoid artefacts, and it appears to be better suited to the spatial de-correlation of texture in images. In the form of quadrature mirror filters (QMFs), a special case of wavelet filters has been known for some time. Wavelet theory generalises the principle of QMFs and provides a broader mathematical basis.

Inspec keywords: data compression; wavelet transforms; quadrature mirror filters; video coding; image texture

Other keywords: spatial texture decorrelation; image texture; subband coding; wavelet transformation; QMF; quadrature mirror filters; DCT blocks; conventional FFT; wavelet theory

Subjects: Image and video coding

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