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<objdefs>
<obj.normal id="karplus" uuid="36d552a0297885559841ed95a25ec5e5589bf5c3" sha="39267e0b01468fb54a8799d8114d535c594a007b">
<sDescription>Karplus (from Faust)</sDescription>
<author>Ricardo Wurmus</author>
<license>GPL</license>
<helpPatch>filter.axh</helpPatch>
<outlets>
<frac32buffer.bipolar name="out" description="filter output"/>
</outlets>
<params>
<bool32.mom name="b" noLabel="true"/>
<frac32.s.map name="a"/>
</params>
<displays/>
<includes>
<include>arm_math.h</include>
</includes>
<attribs/>
<code.declaration><![CDATA[
// convert float to fixed point notation
// * take absolute value
// * multiply with constant to keep precision;
// to get a fixed point at x:y we multiply by 2^y,
// e.g. for 24:8 (24 significant bits before decimal point)
// we multiply f by 2^8 (1<<8).
// * truncate and cast to int32_t
// * invert bits if negative
int32_t floatToFrac32(float f) {
// was 1 000 000 000 and then >> 2
// now is 2^27 = 134 217 728
// 2^32 = 4 294 967 296
// 2^29 = 536 870 912 (3:29)
int32_t preout = int32_t(((f < 0) ? (-f) : f) * (1<<29));
return ((f < 0) ? ~preout : preout);
}
// convert fixed point to float
// * invert bits if sign bit is set (0x08000000, or (1<<27))
// * cast int to float
// * divide by constant to shift decimal point
// * multiply by -1 if sign bit was set
float frac32ToFloat(int32_t frac) {
bool neg = (((1<<27) & frac) != 0);
float res = (float)(neg ? frac : ~frac);
res = res / (float(1<<29));
return (neg ? (-1 * res) : res);
}
float fslider0;
float fVec0[2];
float fRec1[2];
int iRec2[2];
float fslider1;
float fslider2;
int IOTA;
float fVec1[512];
float fslider3;
float fRec0[3];
]]></code.declaration>
<code.init><![CDATA[
fslider0 = 128.0f; // duration or excitation
for (int i=0; i<2; i++) fVec0[i] = 0;
for (int i=0; i<2; i++) fRec1[i] = 0;
for (int i=0; i<2; i++) iRec2[i] = 0;
fslider1 = 0.5f; // level
fslider2 = 0.01f; // attenuation, was 0.1f
IOTA = 0;
for (int i=0; i<512; i++) fVec1[i] = 0;
fslider3 = 128.0f; // duration or excitation
for (int i=0; i<3; i++) fRec0[i] = 0;
]]></code.init>
<code.krate><![CDATA[
float fSlow0 = (1.0f / float(fslider0));
float fSlow1 = float(param_b);
float fSlow2 = (4.656612875245797e-10f * float(fslider1));
float fSlow3 = (0.5f * (1.0f - float(fslider2)));
int iSlow4 = int((int((float(fslider3) - 1.5f)) & 4095));
int32_t* output0 = outlet_out;
for (int i=0; i<BUFSIZE; i++) {
fVec0[0] = fSlow1;
fRec1[0] = ((fRec1[1] + ((fSlow1 - fVec0[1]) > 0.0f)) - (fSlow0 * (fRec1[1] > 0.0f)));
iRec2[0] = (12345 + (1103515245 * iRec2[1]));
fVec1[IOTA&511] = ((fSlow3 * (fRec0[1] + fRec0[2])) + (fSlow2 * (iRec2[0] * (fRec1[0] > 0.0f))));
fRec0[0] = fVec1[(IOTA-iSlow4)&511];
arm_float_to_q31(&fRec0[0], &output0[i], 0);
// output0[i] = floatToFrac32(fRec0[0]);
// post processing
fRec0[2] = fRec0[1]; fRec0[1] = fRec0[0];
IOTA = IOTA+1;
iRec2[1] = iRec2[0];
fRec1[1] = fRec1[0];
fVec0[1] = fVec0[0];
}
]]></code.krate>
</obj.normal>
</objdefs>
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