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<?xml version="1.0"?>
<!DOCTYPE ladspa SYSTEM "ladspa-swh.dtd">
<?xml-stylesheet href="ladspa.css" type="text/css"?>
<ladspa>
<global>
<meta name="maker" value="Steve Harris <steve@plugin.org.uk>"/>
<meta name="copyright" value="GPL"/>
<meta name="properties" value="HARD_RT_CAPABLE"/>
<code><![CDATA[
#include <math.h>
#include "ladspa-util.h"
#define SIN_T_SIZE 1024
#define D_SIZE 256
#define NZEROS 200
/* The non-zero taps of the Hilbert transformer */
static float xcoeffs[] = {
+0.0008103736f, +0.0008457886f, +0.0009017196f, +0.0009793364f,
+0.0010798341f, +0.0012044365f, +0.0013544008f, +0.0015310235f,
+0.0017356466f, +0.0019696659f, +0.0022345404f, +0.0025318040f,
+0.0028630784f, +0.0032300896f, +0.0036346867f, +0.0040788644f,
+0.0045647903f, +0.0050948365f, +0.0056716186f, +0.0062980419f,
+0.0069773575f, +0.0077132300f, +0.0085098208f, +0.0093718901f,
+0.0103049226f, +0.0113152847f, +0.0124104218f, +0.0135991079f,
+0.0148917649f, +0.0163008758f, +0.0178415242f, +0.0195321089f,
+0.0213953037f, +0.0234593652f, +0.0257599469f, +0.0283426636f,
+0.0312667947f, +0.0346107648f, +0.0384804823f, +0.0430224431f,
+0.0484451086f, +0.0550553725f, +0.0633242001f, +0.0740128560f,
+0.0884368322f, +0.1090816773f, +0.1412745301f, +0.1988673273f,
+0.3326528346f, +0.9997730178f, -0.9997730178f, -0.3326528346f,
-0.1988673273f, -0.1412745301f, -0.1090816773f, -0.0884368322f,
-0.0740128560f, -0.0633242001f, -0.0550553725f, -0.0484451086f,
-0.0430224431f, -0.0384804823f, -0.0346107648f, -0.0312667947f,
-0.0283426636f, -0.0257599469f, -0.0234593652f, -0.0213953037f,
-0.0195321089f, -0.0178415242f, -0.0163008758f, -0.0148917649f,
-0.0135991079f, -0.0124104218f, -0.0113152847f, -0.0103049226f,
-0.0093718901f, -0.0085098208f, -0.0077132300f, -0.0069773575f,
-0.0062980419f, -0.0056716186f, -0.0050948365f, -0.0045647903f,
-0.0040788644f, -0.0036346867f, -0.0032300896f, -0.0028630784f,
-0.0025318040f, -0.0022345404f, -0.0019696659f, -0.0017356466f,
-0.0015310235f, -0.0013544008f, -0.0012044365f, -0.0010798341f,
-0.0009793364f, -0.0009017196f, -0.0008457886f, -0.0008103736f,
};
]]></code>
</global>
<plugin label="bodeShifter" id="1431" class="SpectralPlugin">
<name>Bode frequency shifter</name>
<p>A Bode/Moog Frequency Shifter is a popular analogue synth module, it works by shifting all the frequencies of an input signal up or down by a specified frequency. This version shifts in both directions at the same time as its almost no extra work and its often useful to have both directions.</p>
<p>It doesn't actually work in the same way as an analogue Bode/Moog, which use Dome filters as the core, it uses a Hilbert Transformer, which is much simpler to implement in digital systems. The output is very similar though, and people are familiar with the name Bode.</p>
<p>The theory of operation is pretty simple, and uses some clever maths to cancel out the upper or lower sidebands of a ringmodulator applied to the input signal. Read the source if you want more information. The Hilbert Transformet coefficents came from mkfilter, the excellent filter calculator, available at \url{http://www-users.cs.york.ac.uk/~fisher/mkfilter/}.</p>
<callback event="instantiate"><![CDATA[
unsigned int i;
fs = (float)s_rate;
delay = calloc(D_SIZE, sizeof(LADSPA_Data));
sint = calloc(SIN_T_SIZE + 4, sizeof(float));
dptr = 0;
phi = 0.0f;
last_shift = 0.0f;
for (i = 0; i < SIN_T_SIZE + 4; i++) {
sint[i] = sinf(2.0f * M_PI * (float)i / (float)SIN_T_SIZE);
}
]]></callback>
<callback event="cleanup"><![CDATA[
free(plugin_data->delay);
free(plugin_data->sint);
]]></callback>
<callback event="run"><![CDATA[
unsigned long pos;
unsigned int i;
float hilb, rm1, rm2;
float shift_i = last_shift;
int int_p;
float frac_p;
const float shift_c = f_clamp(shift, 0.0f, 10000.0f);
const float shift_inc = (shift_c - last_shift) / (float)sample_count;
const float freq_fix = (float)SIN_T_SIZE / fs;
for (pos = 0; pos < sample_count; pos++) {
delay[dptr] = input[pos];
/* Perform the Hilbert FIR convolution
* (probably FFT would be faster) */
hilb = 0.0f;
for (i = 0; i < NZEROS/2; i++) {
hilb += (xcoeffs[i] * delay[(dptr - i*2) & (D_SIZE - 1)]);
}
/* Calcuate the table positions for the sine modulator */
int_p = f_round(floor(phi));
/* Calculate ringmod1, the transformed input modulated with a shift Hz
* sinewave. This creates a +180 degree sideband at source-shift Hz and
* a 0 degree sindeband at source+shift Hz */
frac_p = phi - int_p;
/* the Hilbert has a gain of pi/2, which we have to correct for, thanks
* Fons! */
rm1 = hilb * 0.63661978f * cube_interp(frac_p, sint[int_p],
sint[int_p+1], sint[int_p+2], sint[int_p+3]);
/* Calcuate the table positions for the cosine modulator */
int_p = (int_p + SIN_T_SIZE / 4) & (SIN_T_SIZE - 1);
/* Calculate ringmod2, the delayed input modulated with a shift Hz
* cosinewave. This creates a 0 degree sideband at source+shift Hz
* and a -180 degree sindeband at source-shift Hz */
rm2 = delay[(dptr - 99) & (D_SIZE - 1)] * cube_interp(frac_p,
sint[int_p], sint[int_p+1], sint[int_p+2], sint[int_p+3]);
/* Output the sum and differences of the ringmods. The +/-180 degree
* sidebands cancel (more of less) and just leave the shifted
* components */
buffer_write(dout[pos], (rm2 - rm1) * 0.5f);
buffer_write(uout[pos], (rm2 + rm1) * 0.5f);
dptr = (dptr + 1) & (D_SIZE - 1);
phi += shift_i * freq_fix;
while (phi > SIN_T_SIZE) {
phi -= SIN_T_SIZE;
}
shift_i += shift_inc;
}
plugin_data->dptr = dptr;
plugin_data->phi = phi;
plugin_data->last_shift = shift_c;
*(plugin_data->latency) = 99;
]]></callback>
<port label="shift" dir="input" type="control" hint="default_0">
<name>Frequency shift</name>
<p>Controls the frequency shift applied to the input signal, in Hz. Note, this is not a pitch shift, so you not get natural sounding results out, it is an audio effect popular with modular synthesists.</p>
<range min="0" max="5000"/>
</port>
<port label="input" dir="input" type="audio">
<name>Input</name>
</port>
<port label="dout" dir="output" type="audio">
<name>Down out</name>
</port>
<port label="uout" dir="output" type="audio">
<name>Up out</name>
</port>
<port label="latency" dir="output" type="control">
<name>latency</name>
</port>
<instance-data label="delay" type="LADSPA_Data *" />
<instance-data label="dptr" type="unsigned int" />
<instance-data label="phi" type="float" />
<instance-data label="fs" type="float" />
<instance-data label="last_shift" type="float" />
<instance-data label="sint" type="float *" />
</plugin>
</ladspa>
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