minidsp.h

Go to the documentation of this file.

 
#ifndef MINIDSP_H
#define MINIDSP_H
 
#include <string.h>
#include <assert.h>
#include <stdlib.h>
#include <math.h>
 
/* M_PI is not guaranteed by the C standard.  Define it if the system didn't. */
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
#include <float.h>
#include <complex.h>
#include <fftw3.h>
 
/* -----------------------------------------------------------------------
 * Basic signal measurement functions
 * -----------------------------------------------------------------------*/
 
double MD_dot(const double *a, const double *b, unsigned N);
 
double MD_entropy(const double *a, unsigned N, bool clip);
 
double MD_energy(const double *a, unsigned N);
 
double MD_power(const double *a, unsigned N);
 
double MD_power_db(const double *a, unsigned N);
 
/* -----------------------------------------------------------------------
 * Signal scaling and conditioning
 * -----------------------------------------------------------------------*/
 
double MD_scale(double in,
                double oldmin, double oldmax,
                double newmin, double newmax);
 
void MD_scale_vec(double *in, double *out, unsigned N,
                  double oldmin, double oldmax,
                  double newmin, double newmax);
 
void MD_fit_within_range(double *in, double *out, unsigned N,
                         double newmin, double newmax);
 
void MD_adjust_dblevel(const double *in, double *out,
                       unsigned N, double dblevel);
 
/* -----------------------------------------------------------------------
 * FFT / Spectrum Analysis
 * -----------------------------------------------------------------------*/
 
void MD_magnitude_spectrum(const double *signal, unsigned N, double *mag_out);
 
void MD_power_spectral_density(const double *signal, unsigned N, double *psd_out);
 
void MD_phase_spectrum(const double *signal, unsigned N, double *phase_out);
 
unsigned MD_stft_num_frames(unsigned signal_len, unsigned N, unsigned hop);
 
void MD_stft(const double *signal, unsigned signal_len,
             unsigned N, unsigned hop,
             double *mag_out);
 
/* -----------------------------------------------------------------------
 * Window generation
 * -----------------------------------------------------------------------*/
 
void MD_Gen_Hann_Win(double *out, unsigned n);
 
/* -----------------------------------------------------------------------
 * Signal generators
 * -----------------------------------------------------------------------*/
 
void MD_sine_wave(double *output, unsigned N, double amplitude,
                  double freq, double sample_rate);
 
void MD_white_noise(double *output, unsigned N, double amplitude,
                    unsigned seed);
 
void MD_impulse(double *output, unsigned N, double amplitude, unsigned position);
 
void MD_chirp_linear(double *output, unsigned N, double amplitude,
                     double f_start, double f_end, double sample_rate);
 
void MD_chirp_log(double *output, unsigned N, double amplitude,
                  double f_start, double f_end, double sample_rate);
 
void MD_square_wave(double *output, unsigned N, double amplitude,
                    double freq, double sample_rate);
 
void MD_sawtooth_wave(double *output, unsigned N, double amplitude,
                      double freq, double sample_rate);
 
/* -----------------------------------------------------------------------
 * Resource cleanup
 * -----------------------------------------------------------------------*/
 
void MD_shutdown(void);
 
/* -----------------------------------------------------------------------
 * Generalized Cross-Correlation (GCC) for delay estimation
 * -----------------------------------------------------------------------
 *
 * Given two microphone signals that captured the same sound source,
 * GCC-PHAT estimates how many samples one signal is delayed relative
 * to the other.  This is the basis of acoustic source localisation.
 *
 * The algorithm:
 *   1. FFT both signals.
 *   2. Multiply one spectrum by the conjugate of the other (cross-spectrum).
 *   3. Apply a weighting (PHAT normalises by magnitude, sharpening the peak).
 *   4. Inverse-FFT back to the time domain.
 *   5. The position of the peak tells you the delay in samples.
 */
 
enum MD_GCC_WEIGHTING_TYPE {
    SIMP, 
    PHAT  
};
 
void MD_get_multiple_delays(const double **sigs, unsigned M, unsigned N,
                            unsigned margin, int weightfunc,
                            int *outdelays);
 
int MD_get_delay(const double *siga, const double *sigb, unsigned N,
                 double *ent, unsigned margin, int weightfunc);
 
void MD_gcc(const double *siga, const double *sigb, unsigned N,
            double *lagvals, int weightfunc);
 
#endif /* MINIDSP_H */