110 lines
3.0 KiB
C
110 lines
3.0 KiB
C
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/* critical-bands.c
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* atsa: ATS analysis implementation
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* Oscar Pablo Di Liscia / Pete Moss / Juan Pampin
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*/
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#include "atsa.h"
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#include <math.h>
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/* Definition of critical band frequency edges, based on data from:
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* Zwicker, Fastl (1990) "Psychoacoustics Facts and Models",
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* Berlin ; New York : Springer-Verlag */
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double ATSA_CRITICAL_BAND_EDGES[ATSA_CRITICAL_BANDS+1] =
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{ 0.0, 100.0, 200.0, 300.0, 400.0, 510.0,
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630.0, 770.0, 920.0, 1080.0, 1270.0,
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1480.0, 1720.0, 2000.0, 2320.0, 2700.0,
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3150.0, 3700.0, 4400.0, 5300.0, 6400.0,
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7700.0, 9500.0, 12000.0, 15500.0, 20000.0 };
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/* private function prototypes */
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void clear_mask(ATS_PEAK *peaks, int peaks_size);
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double compute_slope_r(double val);
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double frq2bark(double frq, double *edges);
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int find_band(double frq, double *edges);
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/* frq2bark
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* ========
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* frequency to bark scale conversion
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*/
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double frq2bark(double frq, double *edges)
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{
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double lo_frq, hi_frq;
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int band;
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if(frq <= 400.0) return(frq * .01);
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if(frq >= 20000.0) return(NIL);
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band = find_band(frq, edges);
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lo_frq = edges[band];
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hi_frq = edges[band+1];
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return(1 + band + fabs(log10(frq/lo_frq) / log10(lo_frq/hi_frq)));
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}
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/* find_band
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* =========
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* returns the critical band number
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* corresponding to frq
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*/
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int find_band(double frq, double *edges)
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{
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int i = 0;
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while(frq > edges[i++]);
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return(i-2);
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}
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/* compute_slope_r
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* ===============
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* computes masking curve's right slope from val
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*/
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double compute_slope_r(double val)
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{
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double i = val - 40.0;
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return(((i > 0.0) ? i : 0.0) * 0.37 - 27.0);
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}
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/* clear_mask
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* ==========
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* clears masking curves
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* peaks: array of peaks representing the masking curve
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* peaks_size: number of peaks in curve
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*/
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void clear_mask(ATS_PEAK *peaks, int peaks_size)
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{
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while(peaks_size--) peaks[peaks_size].smr = 0.0;
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}
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/* evaluate_smr
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* ============
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* evalues the masking curves of an analysis frame
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* setting the peaks smr slot.
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* peaks: pointer to an array of peaks
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* peaks_size: number of peaks
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*/
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void evaluate_smr(ATS_PEAK *peaks, int peaks_size)
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{
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double slope_l = -27.0, slope_r, delta_dB = -50.0;
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double frq_masker, amp_masker, frq_maskee, amp_maskee, mask_term;
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int i, j;
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ATS_PEAK *maskee;
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double *edges = ATSA_CRITICAL_BAND_EDGES;
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clear_mask(peaks, peaks_size);
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if(peaks_size == 1) peaks[0].smr = amp2db_spl(peaks[0].amp);
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else for(i=0; i<peaks_size; i++) {
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maskee = &peaks[i];
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frq_maskee = frq2bark(maskee->frq, edges);
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amp_maskee = amp2db_spl(maskee->amp);
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for(j=0; j<peaks_size; j++)
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if(i != j) {
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frq_masker = frq2bark(peaks[j].frq, edges);
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amp_masker = amp2db_spl(peaks[j].amp);
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slope_r = compute_slope_r(amp_masker);
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mask_term = (frq_masker < frq_maskee) ?
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(amp_masker + delta_dB + (slope_r * (frq_maskee - frq_masker))) :
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(amp_masker + delta_dB + (slope_l * (frq_masker - frq_maskee)));
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if(mask_term > maskee->smr) maskee->smr = mask_term;
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}
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maskee->smr = amp_maskee - maskee->smr;
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}
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}
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