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Diffstat (limited to 'src/lingot-signal.c')
| -rw-r--r-- | src/lingot-signal.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/src/lingot-signal.c b/src/lingot-signal.c new file mode 100644 index 0000000..e675216 --- /dev/null +++ b/src/lingot-signal.c @@ -0,0 +1,153 @@ +//-*- C++ -*- +/* + * lingot, a musical instrument tuner. + * + * Copyright (C) 2004-2007 Ibán Cereijo Graña, Jairo Chapela Martínez. + * + * This file is part of lingot. + * + * lingot is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * lingot is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with lingot; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <math.h> + +#include "lingot-signal.h" + +/* + peak identification functions. + */ + +FLT lingot_signal_get_noise_threshold(LingotConfig* conf, FLT w) +{ + //return 0.5*(1.0 - 0.9*w/M_PI); + return pow(10.0, (conf->noise_threshold_db*(1.0 - 0.9*w/M_PI))/10.0); + //return conf->noise_threshold_un; +} + +//--------------------------------------------------------------------------- + +/* returns the index of the maximun of the buffer x of size N */ +void lingot_signal_get_max(FLT *x, int N, int* Mi) { + register int i; + FLT M; + + M = -1.0; + *Mi = -1; + + for (i = 0; i < N; i++) { + + if (x[i] > M) { + M = x[i]; + *Mi = i; + } + } +} + +//--------------------------------------------------------------------------- + +int lingot_signal_is_peak(LingotConfig* conf, FLT* x, int index) { + register unsigned int j; + //static FLT delta_w_FFT = 2.0*M_PI/conf->FFT_SIZE; // resolution in rads + + // a peak must be greater than noise threshold. + if (x[index] < conf->noise_threshold_nu) + return 0; + + for (j = 0; j < conf->peak_order; j++) { + if (x[index + j] < x[index + j + 1]) + return 0; + if (x[index - j] < x[index - j - 1]) + return 0; + } + return 1; +} + +//--------------------------------------------------------------------------- + +// search the fundamental peak given the spd and its 2nd derivative +int lingot_signal_get_fundamental_peak(LingotConfig* conf, FLT *x, FLT* d2x, + int N) { + register unsigned int i, j, m; + int p_index[conf->peak_number]; + + // at this moment there is no peaks. + for (i = 0; i < conf->peak_number; i++) + p_index[i] = -1; + + unsigned int lowest_index = (unsigned int)ceil(conf->min_frequency*(1.0 + *conf->oversampling/conf->sample_rate)*conf->fft_size); + + if (lowest_index < conf->peak_order) + lowest_index = conf->peak_order; + + // I'll get the PEAK_NUMBER maximum peaks. + for (i = lowest_index; i < N - conf->peak_order; i++) + if (lingot_signal_is_peak(conf, x, i)) { + + // search a place in the maximums buffer, if it doesn't exists, the + // lower maximum is candidate to be replaced. + m = 0; // first candidate. + for (j = 0; j < conf->peak_number; j++) { + if (p_index[j] == -1) { + m = j; // there is a place. + break; + } + + if (d2x[p_index[j]] < d2x[p_index[m]]) + m = j; // search the lowest. + } + + if (p_index[m] == -1) + p_index[m] = i; // there is a place + else if (d2x[i] > d2x[p_index[m]]) + p_index[m] = i; // if greater + } + + FLT maximum = 0.0; + int maximum_index = -1; + + // search the maximum peak + for (i = 0; i < conf->peak_number; i++) + if ((p_index[i] != -1) && (x[p_index[i]] > maximum)) { + maximum = x[p_index[i]]; + maximum_index = p_index[i]; + } + + if (maximum_index == -1) + return N; + + // all peaks much lower than maximum are deleted. + for (i = 0; i < conf->peak_number; i++) + if ((p_index[i] == -1) ||(conf->peak_rejection_relation_nu + *x[p_index[i]] < maximum)) + p_index[i] = N; // there are available places in the buffer. + + // search the lowest maximum index. + for (m = 0, j = 0; j < conf->peak_number; j++) { + if (p_index[j] < p_index[m]) + m = j; + } + + return p_index[m]; +} + +//--------------------------------------------------------------------------- + +// generates a Hamming window of N samples +void lingot_signal_hamming_window(int N, FLT* out) { + register int i; + for (i = 0; i < N; i++) + out[i] = 0.53836 - 0.46164*cos((2.0*M_PI*i)/(N-1)); +} |