The structure of the parametric stereo decoder is shown in Figure 5.3. The mono input signal s1 is first processed by a hybrid QMF analysis filterbank. Subsequently, the hybrid QMF-domain signal s1,m is processed by a decorrelator (D) to result in a second signal D(s1,m). These two input signals are processed by a matrix Rb. Finally, two hybrid QMF synthesis filterbanks generate the two domain–domain output signals 1 and 2. These separate stages will be explained in more detail in the following sections.
The applied filterbank is a hybrid complex-modulated quadrature mirror filter bank (QMF) which is an extension to the filterbank as used in spectral band replication (SBR) techniques [68, 172, 279]. The hybrid QMF analysis filterbank consists of a cascade of two filterbanks. The structure is shown in the left panel of Figure 5.4.
The first filterbank (QMF analysis) is compatible with the filterbank as used in SBR. The sub-band signals which are generated by this first filterbank are obtained by convolving the input signal with a set of analysis filter impulse responses Gm0(n) given by
with g0(n) for n = 0,..., N0 − 1 the prototype ...