fftinv
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## fftinv

fftinv — Complex-to-complex Inverse Fast Fourier Transform.

## Description

Applies an Inverse Fast Fourier Transform to a complex-value input 1-dimensional array producing a complex-valued output. The output is another array containing the complex-valued signal, and both arrays are arranged in interleaved real-imaginary format. The output array will have the same size as the input, and the transform size will be equivalent to half of the length of the array. Non-power-of-two transforms are limited to even sizes with not too many factors.

## Syntax

    kout[] fftinv kin[]

## Performance

kout[] -- output array containing the complex-valued output. It will be created if it does not exist.

kin[] -- input array containing the complex-valued input.

## Examples

Here is an example of the fftinv opcode. It uses the file ifft.csd.

Example 455. Example of the fftinv opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

    <CsoundSynthesizer>
    <CsOptions>
    -d -o dac
    </CsOptions>
    <CsInstruments>
    ksmps = 64

    instr 1
    ifftsize = 1024
    kcnt init 0
    kIn[] init  ifftsize
    kOut[] init ifftsize

    a1 oscili 0dbfs/2, 440

    if kcnt >= ifftsize then
     kCmplx[] r2c kIn
     kSpec[] fft kCmplx
     kCmplx ifftinv kSpec
     kOut c2r kCmplx
     kcnt = 0
    endif

    kIn[] shiftin a1
    a2 shiftout kOut
    kcnt += ksmps
       out a2
    endin
    </CsInstruments>
    <CsScore>
    i1 0 10
    </CsScore>
    </CsoundSynthesizer>

## See Also

Vectorial opcodes, array opcodes

## Credits

Author: Victor Lazzarini
NUI Maynooth
2014

New in version 6.04

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