rifft — Complex-to-real Inverse Fast Fourier Transform.
Applies an Inverse Fast Fourier Transform to a complex-value input 1-dimensional array producing a real-valued output. The output is another array containing the real-valued signal. If the input array is power-of-two, the output array size will match the input size. Otherwise, the output will have two fewer values (input size - 2).
kout[] -- output array containing the real-valued output. It will be created if it does not exist.
kin[] -- input array containing the complex input.
Here is an example of the rifft opcode. It uses the file irfft.csd.
Example 902. Example of the rifft 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 needs to be an integer div of hopsize ksmps = 64 instr 1 ihopsize = 256 ; hopsize ifftsize = 1024 ; FFT size iolaps = ifftsize/ihopsize ; overlaps ibw = sr/ifftsize ; bin bandwidth kcnt init 0 ; counting vars krow init 0 kOla[] init ifftsize ; overlap-add buffer kIn[] init ifftsize ; input buffer kOut[][] init iolaps, ifftsize ; output buffers a1 diskin2 "fox.wav",1,0,1 ; audio input /* every hopsize samples */ if kcnt == ihopsize then /* window and take FFT */ kWin[] window kIn,krow*ihopsize kSpec[] rfft kWin /* filter between high and low freqs */ ilow = 0 ihigh = 1000 ki = int(ilow/ibw) until ki == int(ihigh/ibw) do kSpec[ki] = 0 ki += 1 od /* IFFT + window */ kRow[] rifft kSpec kWin window kRow, krow*ihopsize /* place it on out buffer */ kOut setrow kWin, krow /* zero the ola buffer */ kOla = 0 /* overlap-add */ ki = 0 until ki == iolaps do kRow getrow kOut, ki kOla = kOla + kRow ki += 1 od /* update counters */ krow = (krow+1)%iolaps kcnt = 0 endif /* shift audio in/out of buffers */ kIn shiftin a1 a2 shiftout kOla out a2/iolaps /* increment counter */ kcnt += ksmps endin </CsInstruments> <CsScore> i1 0 10 </CsScore> </CsoundSynthesizer>