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# grain3

grain3 -- Generate granular synthesis textures with more user control.

## Description

Generate granular synthesis textures. grain2 is simpler to use but grain3 offers more control.

## Syntax

ar grain3 kcps, kphs, kfmd, kpmd, kgdur, kdens, imaxovr, kfn, iwfn, kfrpow, kprpow [, iseed] [, imode]

## Initialization

imaxovr -- maximum number of overlapping grains. The number of overlaps can be calculated by (kdens * kgdur); however, it can be overestimated at no cost in rendering time, and a single overlap uses (depending on system) 16 to 32 bytes of memory.

iwfn -- function table containing window waveform (Use GEN20 to calculate iwfn).

irpow (optional, default=0) -- this value controls the distribution of grain frequency variation. If irpow is positive, the random distribution (x is in the range -1 to 1) is

abs(x) ^ ((1 / irpow) - 1)

; for negative irpow values, it is

(1 - abs(x)) ^ ((-1 / irpow) - 1)

. Setting irpow to -1, 0, or 1 will result in uniform distribution (this is also faster to calculate). The image below shows some examples for irpow. The default value of irpow is 0.

A graph of distributions for different values of irpow.

iseed (optional, default=0) -- seed value for random number generator (positive integer in the range 1 to 2147483646 (2 ^ 31 - 2)). Zero or negative value seeds from current time (this is also the default).

imode (optional, default=0) -- sum of the following values:

- 64: synchronize start phase of grains to kcps.

- 32: start all grains at integer sample location. This may be faster in some cases, however it also makes the timing of grain envelopes less accurate.

- 16: do not render grains with start time less than zero. (see the image below; this option turns off grains marked with red on the image).

- 8: interpolate window waveform (slower).

- 4: do not interpolate grain waveform (fast, but lower quality).

- 2: grain frequency is continuously modified by kcps and kfmd (by default, each grain keeps the frequency it was launched with). This may be slower at high control rates. It also controls phase modulation (kphs).

- 1: skip initialization.

A diagram showing grains with a start time less than zero in red.

## Performance

ar -- output signal.

kcps -- grain frequency in Hz.

kphs -- grain phase. This is the location in the grain waveform table, expressed as a fraction (between 0 to 1) of the table length.

kfmd -- random variation (bipolar) in grain frequency in Hz.

kpmd -- random variation (bipolar) in start phase.

kgdur -- grain duration in seconds. kgdur also controls the duration of already active grains (actually the speed at which the window function is read). This behavior does not depend on the imode flags.

kdens -- number of grains per second.

kfrpow -- distribution of random frequency variation (see irpow).

kprpow -- distribution of random phase variation (see irpow). Setting kphs and kpmd to 0.5, and kprpow to 0 will emulate grain2.

kfn -- function table containing grain waveform. Table number can be changed at k-rate (this is useful to select from a set of band-limited tables generated by GEN30, to avoid aliasing).

| Note
| grain3 internally uses the same random number generator as rnd31. So reading its documentation is also recommended.

## Examples

Here is an example of the grain3 opcode. It uses the files grain3.orc and grain3.sco.

Example 1. Example of the grain3 opcode.

    /* grain3.orc */
    sr	=  48000
    kr	=  1000
    ksmps   =  48
    nchnls	=  1

    /* Bartlett window */
    itmp	ftgen 1, 0, 16384, 20, 3, 1
    /* sawtooth wave */
    itmp	ftgen 2, 0, 16384, 7, 1, 16384, -1
    /* sine */
    itmp	ftgen 4, 0, 1024, 10, 1
    /* window for "soft sync" with 1/32 overlap */
    itmp	ftgen 5, 0, 16384, 7, 0, 256, 1, 7936, 1, 256, 0, 7936, 0
    /* generate bandlimited sawtooth waves */
    itmp	ftgen 3, 0, 4096, -30, 2, 1, 2048
    icnt	=  0
    loop01:
    ; 100 tables for 8 octaves from 30 Hz
    ifrq	=  30 * exp(log(2) * 8 * icnt / 100)
    itmp	ftgen icnt + 100, 0, 4096, -30, 3, 1, sr / (2 * ifrq)
    icnt	=  icnt + 1
    	if (icnt < 99.5) igoto loop01
    /* convert frequency to table number */
    #define FRQ2FNUM(xout'xcps'xbsfn) #

    $xout	=  int(($xbsfn) + 0.5 + (100 / 8) * log(($xcps) / 30) / log(2))
    $xout	limit $xout, $xbsfn, $xbsfn + 99

    #

    /* instr 1: pulse width modulated grains */

    	instr 1

    kfrq	=  523.25		; frequency
    $FRQ2FNUM(kfnum'kfrq'100)	; table number
    kfmd	=  kfrq * 0.02		; random variation in frequency
    kgdur	=  0.2			; grain duration
    kdens	=  200			; density
    iseed	=  1			; random seed

    kphs	oscili 0.45, 1, 4	; phase

    a1	grain3	kfrq, 0, kfmd, 0.5, kgdur, kdens, 100,		\
    		kfnum, 1, -0.5, 0, iseed, 2
    a2	grain3	kfrq, 0.5 + kphs, kfmd, 0.5, kgdur, kdens, 100,	\
    		kfnum, 1, -0.5, 0, iseed, 2

    ; de-click
    aenv	linseg 0, 0.01, 1, p3 - 0.05, 1, 0.04, 0, 1, 0

    	out aenv * 2250 * (a1 - a2)

    	endin

    /* instr 2: phase variation */

    	instr 2

    kfrq	=  220			; frequency
    $FRQ2FNUM(kfnum'kfrq'100)	; table number
    kgdur	=  0.2			; grain duration
    kdens	=  200			; density
    iseed	=  2			; random seed

    kprdst	expon 0.5, p3, 0.02	; distribution

    a1	grain3	kfrq, 0.5, 0, 0.5, kgdur, kdens, 100,		\
    		kfnum, 1, 0, -kprdst, iseed, 64

    ; de-click
    aenv	linseg 0, 0.01, 1, p3 - 0.05, 1, 0.04, 0, 1, 0

    	out aenv * 1500 * a1

    	endin

    /* instr 3: "soft sync" */

    	instr 3

    kdens	=  130.8		; base frequency
    kgdur	=  2 / kdens		; grain duration

    kfrq	expon 880, p3, 220	; oscillator frequency
    $FRQ2FNUM(kfnum'kfrq'100)	; table number

    a1	grain3 kfrq, 0, 0, 0, kgdur, kdens, 3, kfnum, 5, 0, 0, 0, 2
    a2	grain3 kfrq, 0.667, 0, 0, kgdur, kdens, 3, kfnum, 5, 0, 0, 0, 2

    ; de-click
    aenv	linseg 0, 0.01, 1, p3 - 0.05, 1, 0.04, 0, 1, 0

    	out aenv * 10000 * (a1 - a2)

    	endin
    /* grain3.orc */

    /* grain3.sco */
    t 0 60
    i 1 0 3
    i 2 4 3
    i 3 8 3
    e
    /* grain3.sco */

## See Also

grain2

## Credits

Author: Istvan Varga

New in version 4.15

Updated April 2002 by Istvan Varga

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