A method to initialize free parameters in lattice structure of arbitrary-length linear phase perfect reconstruction filter bank

The optimization of the free parameters in the lattice structure of linear phase perfect reconstruction filter bank (LPPRFB) is commonly highly nonlinear, therefore the free parameters should be carefully initialized. Such methods have been published for constrained-length LPPRFB (CLLPPRFB), i.e. LPPRFB with filter length MK, where M is the decimation factor and K is an integer. In contrast to CLLPPRFB, arbitrary-length LPPRFB (ALLPPRFB) [i.e. LPPRFB with filter length MK+β, where β is an integer between 0 and M] provides more choices of filter banks, offering better trade-off between filter length and filter performance. Nevertheless, as far as we know there is no systematic study on initializing the free parameters in the lattice structure of ALLPPRFB, and the required method cannot be easily generalized from those for CLLPPRFB. To address this issue, an initialization method will be described in this paper that initializes a longer ALLPPRFB by a shorter one, and the length difference between the longer and the shorter filter banks can be any number allowed by an ALLPPRFB system. The efficiency of the proposed method will be shown by design examples and image compression experiments.