[PD] Fast convolution of 2 tables using FFT

[JF]

Well, I should say, time domain convolution, using multiplication in the frequency domain ;)

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On Sun, 24/1/16, JF <saintidle at yahoo.com> wrote:

 Subject: Fast convolution of 2 tables using FFT
 To: "pd list" <pd-list at iem.at>, "Me" <saintidle at yahoo.com>
 Date: Sunday, 24 January, 2016, 21:01
 
 Hi all,
 
 I decided to implement my own patch that does frequency
 domain convolution of two tables.
 
 Have a look at the FFTTry02Long03.pd file and you will need
 the attached abstractions and 
 iem_tab [tab_complex_mul] (in the path for vanilla or just
 imported with pd-extended).
 
 It's very fast compared to iem_tab's [tab_conv] but the
 output doesn't exactly match, there is 
 some error. It's small and I'm thinking it's because of the
 blocksize being very large to fft~ the 
 tables all in one go. The ifft~ needs a very large division
 (blocksize) to normalise the gains 
 so I'm presuming there's some number precision funniness
 going on here? If anyone could 
 chime in on this?
 
 Any feedback/improvement ideas would be greatly
 appreciated.
 
 Thanks in advance,
 John.