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GEN20

Generates functions of different windows.

These windows are usually used for spectrum analysis or for grain envelopes.

Syntax

f # time size 20 window max [opt]

Initialization

size -- number of points in the table. Must be a power of 2 ( + 1).

window -- Type of window to generate:

  • 1 = Hamming
  • 2 = Hanning
  • 3 = Bartlett ( triangle)
  • 4 = Blackman ( 3-term)
  • 5 = Blackman - Harris ( 4-term)
  • 6 = Gaussian
  • 7 = Kaiser
  • 8 = Rectangle
  • 9 = Sinc

max -- For negative p4 this will be the absolute value at window peak point. If p4 is positive or p4 is negative and p6 is missing the table will be post-rescaled to a maximum value of 1.

opt -- Optional argument required by the Gaussian window, the Kaiser window and the Sinc window.

Examples

f   1   0   1024   20    5

This creates a function which contains a 4 - term Blackman - Harris window with maximum value of 1.

f   1   0   1024   -20   2   456

This creates a function that contains a Hanning window with a maximum value of 456.

f   1   0   1024   -20   1

This creates a function that contains a Hamming window with a maximum value of 1.

f   1   0   1024   20    7   1   2

This creates a function that contains a Kaiser window with a maximum value of 1. The extra argument specifies how "open" the window is, for example a value of 0 results in a rectangular window and a value of 10 in a Hamming like window.

f   1   0   1024   20    6   1   2

This creates a function that contains a Gaussian window with a maximum value of 1. The extra argument specifies how broad the window is, as the standard deviation of the curve; in this example the s.d. is 2. The default value is 1.

f   1   0   1024   20    9   1   3

This creates a function that contains a Sinc window with a maximum value of 1. The extra argument specifies the range of the function as multiple of π. The default value is 1.

For all diagrams, see Window Functions

Here is an example of the GEN20 routine. It uses the file gen20.csd.

Example of the GEN20 routine.
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<CsoundSynthesizer> 
<CsOptions> 
; Select audio/midi flags here according to platform 
-odac     ;;;realtime audio out 
;-iadc    ;;;uncomment -iadc if realtime audio input is needed too 
; For Non-realtime ouput leave only the line below: 
; -o gen20.wav -W ;;; for file output any platform 
</CsOptions> 
<CsInstruments> 

sr = 44100 
ksmps = 32 
nchnls = 2 
0dbfs  = 1 

instr 1 

insnd   = 10                            ;"marimba.aif"
ibasfrq = 44100 / ftlen(insnd)          ;use original sample rate of insnd file 

kamp   expseg .001, p3/2, .7, p3/2, .8  ;envelope
kpitch line ibasfrq, p3, ibasfrq * .8 
kdens  line 600, p3, 10 
kaoff  line 0, p3, .1
kpoff  line 0, p3, ibasfrq * .5 
kgdur  line .04, p3, .001               ;shorten duration of grain during note
imaxgdur =  .5 
igfn = p4                               ;different windows
asigL  grain kamp, kpitch, kdens, kaoff, kpoff, kgdur, insnd, igfn, imaxgdur, 0.0 
asigR  grain kamp, kpitch, kdens, kaoff, kpoff, kgdur, insnd, igfn, imaxgdur, 0.0 
       outs asigL, asigR

endin 
</CsInstruments> 
<CsScore> 
f1  0 512  20 2         ;Hanning window 
f2  0 512  20 6 1       ;Gaussian window 
f10 0 16384 1 "marimba.aif" 0 0 0 

i1 0 5 1                ;use Hanning window 
i1 + 5 2                ;use Gaussian window
e 
</CsScore> 
</CsoundSynthesizer>

These are the diagrams of the waveforms of the GEN20 routines, as used in the example:

f 1 0 512 20 2 - Hanning window
f 1 0 512 20 2 - Hanning window
f 2 0 512 20 6 1 - Gaussian window
f 2 0 512 20 6 1 - Gaussian window

Credits

Author: Paris Smaragdis
MIT, Cambridge
1995

Author: John ffitch
University of Bath/Codemist Ltd.
Bath, UK

New in Csound version 3.2

Optional argument to Gaussian added in 5.10