A Quadrature Mirror Filter (QMF) bank is used by MPEG-4 SBR decoder. QMF consists of:
QMF filterbanks use the functions given below in low power (LP) and high quality (HQ) modes. Each mode is characterized by three function groups:
To use the SBR_QMF functions, initialize the corresponding filter specification structure, which contains tables of twiddle factors and internal buffer. To allocate memory and initialize the structure, call ipps(**)FilterInitAlloc_SBR_(***) functions, where (**) is a function group name, that is Analysis, Synthesis or SynthesisDown, and (***) is a flavor descriptor (for example, _SBRHQ_32s32sc, _SBRLP_32s). Currently, this method of the specification structure initialization is implemented only for operations on fixed-point signal.
Alternatively, the structure can be initialized by functions for initialization and size getting. In that case, the general operational algorithm is as follows:
The use of the functions described in this section is demonstrated in Intel® IPP Samples downloadable from http://www.intel.com/cd/software/products/asmo-na/eng/220046.htm.
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