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<p class="MsoNormal">The general set of vocoder problems mentioned here yield to a specific digital approach.</p>
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<p class="MsoNormal">First, the need for MANY (topographically similar) filters with unknown or uncertain parameters is an obvious job for programming.</p>
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<p class="MsoNormal">Second, obviously, the equivalent of filtering can be done by taking an FFT (analysis), custom weighting<span style=""> </span>the frequency domain description (the dynamics) and inverting the thusly modified FFT (synthesis).</p>
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<p class="MsoNormal">Thirdly, since the FFT frequencies are equally spaced in Hz (requiring huge FFT sizes) the FFT is NOT well-suited to the audio/speech problem. Instead, look at the well-studied approach of MULTI-RATE DSP where lower rates at lower frequencies
are used. <span style=""> </span>(It’s magic). <span style=""> </span>Things like “perfect-reconstruction filers”.<span style="">
</span>See: P.P. Vaidyanathan “Multirate Systems and Filter Banks” (Prentice-Hall, 1993) and N.J. Fliege, “Multirate Digital Signal Processing: Multirate Systems, Filter Banks, Wavelets” (Wiley 1994).</p>
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<p class="MsoNormal"><span style="font-size:10pt">A simple introductfion: </span><a href="http://electronotes.netfirms.com/AN358.pdf" class="OWAAutoLink" id="LPlnk604580" style="font-size:10pt" previewremoved="true">http://electronotes.netfirms.com/AN358.pdf</a><br>
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<p class="MsoNormal">But first of all – What are you hoping to accomplish?<span style="">
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