grain2
grain2 — Easy-to-use granular synthesis texture generator.
Description
Generate granular synthesis textures. grain2 is simpler to use, but grain3 offers more control.
Initialization
iovrlp -- (fixed) number of overlapping grains.
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.]](images/grain2_rand-448x289.png)
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 (231 - 2)). Zero or negative value seeds from current time (this is also the default).
imode (optional default=0) -- sum of the following values:
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8: interpolate window waveform (slower).
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4: do not interpolate grain waveform (fast, but lower quality).
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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.
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1: skip initialization.
Performance
ares -- output signal.
kcps -- grain frequency in Hz.
kfmd -- random variation (bipolar) in grain frequency in Hz.
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.
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]](images/note.png)
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Note |
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grain2 internally uses the same random number generator as rnd31. So reading its documentation is also recommended. |
Examples
Here is an example of the grain2 opcode. It uses the file grain2.csd.
Example 432. Example of the grain2 opcode.
See the sections Real-time Audio and Command Line Flags for more information on using command line flags.
<CsoundSynthesizer> <CsOptions> ; Select audio/midi flags here according to platform ; Audio out Audio in No messages -odac -iadc -d ;;;RT audio I/O ; For Non-realtime ouput leave only the line below: ; -o grain2.wav -W ;;; for file output any platform </CsOptions> <CsInstruments> sr = 48000 kr = 750 ksmps = 64 nchnls = 2 /* square wave */ i_ ftgen 1, 0, 4096, 7, 1, 2048, 1, 0, -1, 2048, -1 /* window */ i_ ftgen 2, 0, 16384, 7, 0, 4096, 1, 4096, 0.3333, 8192, 0 /* sine wave */ i_ ftgen 3, 0, 1024, 10, 1 /* room parameters */ i_ ftgen 7, 0, 64, -2, 4, 50, -1, -1, -1, 11, \ 1, 26.833, 0.05, 0.85, 10000, 0.8, 0.5, 2, \ 1, 1.753, 0.05, 0.85, 5000, 0.8, 0.5, 2, \ 1, 39.451, 0.05, 0.85, 7000, 0.8, 0.5, 2, \ 1, 33.503, 0.05, 0.85, 7000, 0.8, 0.5, 2, \ 1, 36.151, 0.05, 0.85, 7000, 0.8, 0.5, 2, \ 1, 29.633, 0.05, 0.85, 7000, 0.8, 0.5, 2 ga01 init 0 /* generate bandlimited square waves */ i0 = 0 loop1: imaxh = sr / (2 * 440.0 * exp(log(2.0) * (i0 - 69) / 12)) i_ ftgen i0 + 256, 0, 4096, -30, 1, 1, imaxh i0 = i0 + 1 if (i0 < 127.5) igoto loop1 instr 1 p3 = p3 + 0.2 /* note velocity */ iamp = 0.0039 + p5 * p5 / 16192 /* vibrato */ kcps oscili 1, 8, 3 kenv linseg 0, 0.05, 0, 0.1, 1, 1, 1 /* frequency */ kcps = (kcps * kenv * 0.01 + 1) * 440 * exp(log(2) * (p4 - 69) / 12) /* grain ftable */ kfn = int(256 + 69 + 0.5 + 12 * log(kcps / 440) / log(2)) /* grain duration */ kgdur port 100, 0.1, 20 kgdur = kgdur / kcps a1 grain2 kcps, kcps * 0.02, kgdur, 50, kfn, 2, -0.5, 22, 2 a1 butterlp a1, 3000 a2 grain2 kcps, kcps * 0.02, 4 / kcps, 50, kfn, 2, -0.5, 23, 2 a2 butterbp a2, 12000, 8000 a2 butterbp a2, 12000, 8000 aenv1 linseg 0, 0.01, 1, 1, 1 aenv2 linseg 3, 0.05, 1, 1, 1 aenv3 linseg 1, p3 - 0.2, 1, 0.07, 0, 1, 0 a1 = aenv1 * aenv3 * (a1 + a2 * 0.7 * aenv2) ga01 = ga01 + a1 * 10000 * iamp endin /* output instr */ instr 81 i1 = 0.000001 aLl, aLh, aRl, aRh spat3di ga01 + i1*i1*i1*i1, 3.0, 4.0, 0.0, 0.5, 7, 4 ga01 = 0 aLl butterlp aLl, 800.0 aRl butterlp aRl, 800.0 outs aLl + aLh, aRl + aRh endin </CsInstruments> <CsScore> t 0 60 i 1 0.0 1.3 60 127 i 1 2.0 1.3 67 127 i 1 4.0 1.3 64 112 i 1 4.0 1.3 72 112 i 81 0 6.4 e </CsScore> </CsoundSynthesizer>