On Mon, Jan 02, 2006 at 11:37:54PM +0200, Sergei Steshenko wrote: > So, how are going to implement a central frequency which is > not a multiple of (Fs / N) in a DFT equalizer ? > > That is, what data resulting from direct DFT represents such frequencies ?
A weighted sum of some DFT outputs, instead of just one of them. Look at what you have now. You do a forward FFT and get N complex values A [i]. You multiply each of these A [i] by some factor, and then do an IFFT. The second step can be regarded as the multiplication of the vector A [i] by a diagonal matrix. Using central frequencies in between the 'integer' bins would just mean this matrix is no longer diagonal. In practice it would become a band matrix and still be quite sparse, and the product can be done efficiently. Once you have the matrix instead of the term by term product, the windowing can also be absorbed into it. -- FA ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
