Wavelet packet decomposition

Summary

The wavelet packet decomposition generalizes the discrete wavelet transform. At every level it splits both the approximation and the detail coefficients again. The result is a full binary tree of coefficient sequences, which splits the frequency axis into bands of equal width instead of octaves. Each admissible subtree of this tree gives an orthonormal basis, so one signal has a very large library of bases to choose from. A best-basis search picks the subtree that represents a given signal most economically, which is useful in compression and denoising.