48 lines
1.8 KiB
C
48 lines
1.8 KiB
C
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#include <Python.h>
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#include <stdlib.h>
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#include <math.h>
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#include <complex.h>
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#include "quisk.h"
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// If you set add_extern_demod in your config file, you will get another
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// button that will call this module. Change it to what you want. Save
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// a copy because new releases of Quisk will overwrite this file.
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//
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// NOTE: NEW RELEASES OF QUISK WILL OVERWRITE THIS FILE!
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int quisk_extern_demod(complex double * cSamples, int nSamples, double decim)
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{ // Filter and demodulate the I/Q samples into audio play samples.
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// cSamples: The input I/Q samples, and the output stereo play samples.
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// nSamples: The number of input samples; maximum is SAMP_BUFFER_SIZE.
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// decim: The decimation needed (1.0 for no decimation).
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// The output play samples are stereo, and are placed into cSamples.
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// The return value is the number of output samples = nSamples / decim.
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// See quisk.h for useful data in quisk_sound_state. For example, the
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// sample rate is quisk_sound_state.sample_rate. If you need decimation,
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// look at iDecimate() and fDecimate() in quisk.c.
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int i;
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double d, di;
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complex double cx;
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static complex double fm_1 = 10; // Sample delayed by one
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static complex double fm_2 = 10; // Sample delayed by two
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if (fabs (decim - 1.0) > 0.001) // no provision for decimation
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return 0;
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for (i = 0; i < nSamples; i++) { // narrow FM
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cx = cSamples[i];
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di = creal(fm_1) * (cimag(cx) - cimag(fm_2)) -
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cimag(fm_1) * (creal(cx) - creal(fm_2));
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d = creal(fm_1) * creal(fm_1) + cimag(fm_1) * cimag(fm_1);
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if (d == 0) // I don't think this can happen
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di = 0;
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else
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di = di / d * quisk_sound_state.sample_rate;
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fm_2 = fm_1; // fm_2 is sample cSamples[i - 2]
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fm_1 = cx; // fm_1 is sample cSamples[i - 1]
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cSamples[i] = di + I * di; // monophonic sound, two channels
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}
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return nSamples; // Number of play samples
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}
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