pol2rect

pol2rect — Polar to rectangular format conversion.

Description

Converts an input array in magnitude-phase format to real-imaginary format.

Syntax

kout[] pol2rect kin[]
kout[] pol2rect kmags[], kphs[]

Performance

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

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

kmags[] -- input array containing the real-valued magnitude input. This is expected to contain only the non-negative spectrum (0 to Nyquist, inclusive).

kphs[] -- input array containing the real-valued phase input. This is expected to contain only the non-negative spectrum (0 to Nyquist, inclusive).

NB: the second version of the opcode with two inputs is designed to produce a "packed" real FFT spectrum where the two positions in the array contain the real parts of zero Hz and Nyquist frequency. Therefore the output array length will be 2*L - 2, where L is the length of the input arrays (which should match).

Examples

Here is an example of the pol2rect opcode. It uses the file pol2rect.csd.

Example 789. Example of the pol2rect 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
   
   kSpec rect2pol kSpec 
   
   /* reduce mags between high and low freqs */
   ilow = 0
   ihigh = 1000
   ki = int(ilow/ibw)
   until ki >= int(ihigh/ibw) do
     kSpec[ki] = kSpec[ki]*0.1
     ki += 2
   od
   
   kSpec pol2rect kSpec
   
   /* 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>

See Also

Vectorial opcodes, array opcodes

Credits

Author: Victor Lazzarini
NUI Maynooth
2014

New in version 6.04