ECE
Abstract
In conventional speech processing applications, speech signal is encoded using fixed number of bits over the entire speech signal band. During the process, the bandwidth requirement for speech transmission is relatively high which is of concern. The QMF (Quadrature Mirror Filter) banks are the fundamental building blocks for spectral splitting. The MF structure allows spectral decomposition into contiguous overlapping sub bands in such a way that aliasing incurred in the initial “analysis” stage is eliminated during signal reconstruction by the “synthesis” stage. The technique is developed to design the so-called perfect reconstruction QMF bank, which allows complete elimination of amplitude and phase distortion of the reconstructed signal. A QMF bank can be formed from FIR or IIR filters. The aim of the paper is to design a QMF filter and then pass a speech signal through it. The low pass filtered signal is decimated and encoded with more number of bits and high pass filtered signal is also decimated and encoded with less number of bits. These two bit streams are multiplexed and transmitted. In receiver side the received signal is de-multiplexed and decoded. The signal is passed through the interpolators and then through the synthesis filter so as to reconstruct the speech signal .The reconstructed signal is compared with the original speech signal.
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