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cxvec/math: Add helper to find the N highest energy values in vector

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
master
Sylvain Munaut 6 years ago
parent
commit
e82886ad0e
  1. 3
      include/osmocom/dsp/cxvec_math.h
  2. 45
      src/cxvec_math.c

3
include/osmocom/dsp/cxvec_math.h

@ -103,6 +103,9 @@ osmo_cxvec_correlate(const struct osmo_cxvec *f, const struct osmo_cxvec *g,
float complex
osmo_cxvec_interpolate_point(const struct osmo_cxvec *cv, float pos);
int
osmo_cxvec_peaks_scan(const struct osmo_cxvec *cv, int *peaks_idx, int N);
/*! \brief Various possible peak finding algorithms */
enum osmo_cxvec_peak_alg {
/*! \brief Weigthed position for the max pwr window */

45
src/cxvec_math.c

@ -428,6 +428,51 @@ osmo_cxvec_interpolate_point(const struct osmo_cxvec *cv, float pos)
return val;
}
/*! \brief Find the index of the N highest energy (\f$|x|^2\f$) peaks
* \param[in] cv Input complex vector
* \param[out] peaks_idx Return array of the peak indexes
* \param[in] Size of the \ref peaks_idx return array
* \returns Number of peaks (will be N if there is enough points)
*/
int
osmo_cxvec_peaks_scan(const struct osmo_cxvec *cv, int *peaks_idx, int N)
{
int i, j;
float peaks_mag[N];
/* Pre-init */
for (i=0; i<N; i++) {
peaks_idx[i] = -1;
peaks_mag[i] = 0.0f;
}
/* Scan all */
for (i=0; i<cv->len; i++)
{
/* Magnitude */
float mag = osmo_normsqf(cv->data[i]);
/* Worth it ? */
if (mag < peaks_mag[N-1])
continue;
/* Find insertion point in sorted array and pre-move */
for (j=N-1; j>0; j--) {
if (mag < peaks_mag[j-1])
break;
peaks_mag[j] = peaks_mag[j-1];
peaks_idx[j] = peaks_idx[j-1];
}
/* Do the insert */
peaks_mag[j] = mag;
peaks_idx[j] = i;
}
return i < N ? i : N;
}
/*! \brief Find the maximum energy (\f$|x|^2\f$) peak in a sequence
* \param[in] cv Input complex vector
* \param[in] win_size Size of the window (for algorithms using windows)

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