mirror of https://github.com/mpv-player/mpv
122 lines
3.2 KiB
C
122 lines
3.2 KiB
C
#include <inttypes.h>
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#include <math.h>
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static double desired_7kHz_lowpass[] = {1.0, 0.0};
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static double weights_7kHz_lowpass[] = {0.2, 2.0};
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double *calc_coefficients_7kHz_lowpass(int rate)
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{
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double *result = (double *)malloc(32*sizeof(double));
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double bands[4];
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bands[0] = 0.0; bands[1] = 6800.0/rate;
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bands[2] = 8500.0/rate; bands[3] = 0.5;
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remez(result, 32, 2, bands,
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desired_7kHz_lowpass, weights_7kHz_lowpass, BANDPASS);
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return result;
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}
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#if 0
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static double desired_125Hz_lowpass[] = {1.0, 0.0};
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static double weights_125Hz_lowpass[] = {0.2, 2.0};
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double *calc_coefficients_125Hz_lowpass(int rate)
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{
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double *result = (double *)malloc(256*sizeof(double));
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double bands[4];
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bands[0] = 0.0; bands[1] = 125.0/rate;
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bands[2] = 175.0/rate; bands[3] = 0.5;
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remez(result, 256, 2, bands,
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desired_125Hz_lowpass, weights_125Hz_lowpass, BANDPASS);
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return result;
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}
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#endif
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int16_t firfilter(int16_t *buf, int pos, int len, int count, double *coefficients)
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{
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double result = 0.0;
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int count1, count2;
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int16_t *ptr;
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if (pos >= count) {
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pos -= count;
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count1 = count; count2 = 0;
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}
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else {
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count2 = pos;
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count1 = count - pos;
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pos = len - count1;
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}
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//fprintf(stderr, "pos=%d, count1=%d, count2=%d\n", pos, count1, count2);
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// high part of window
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ptr = &buf[pos];
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while (count1--) result += *ptr++ * *coefficients++;
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// wrapped part of window
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while (count2--) result += *buf++ * *coefficients++;
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return result;
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}
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void dump_filter_coefficients(double *coefficients)
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{
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int i;
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fprintf(stderr, "pl_surround: Filter coefficients are: \n");
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for (i=0; (i<32); i++) {
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fprintf(stderr, " [%2d]: %23.20f\n", i, coefficients[i]);
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}
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}
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#ifdef TESTING
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#define PI 3.1415926536
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// For testing purposes, fill a buffer with some sine-wave tone
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void sinewave(int16_t *output, int samples, int incr, int freq, double phase, int samplerate)
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{
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double radians_per_sample = 2*PI / ((0.0+samplerate) / freq), r;
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//fprintf(stderr, "samples=%d tone freq=%d, samplerate=%d, radians/sample=%f\n",
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// samples, freq, samplerate, radians_per_sample);
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r = phase;
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while (samples--) {
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*output = sin(r)*10000; output = &output[incr];
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r += radians_per_sample;
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}
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}
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// Pass various frequencies through a FIR filter and report amplitudes
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void testfilter(double *coefficients, int count, int samplerate)
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{
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int16_t wavein[8192]; //, waveout[2048];
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int sample, samples, maxsample, minsample, totsample;
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int nyquist=samplerate/2;
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int freq, i;
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for (freq=25; freq<nyquist; freq+=25) {
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// Make input tone
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sinewave(wavein, 8192, 1, freq, 0.0, samplerate);
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//for (i=0; i<32; i++)
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// fprintf(stderr, "%5d\n", wavein[i]);
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// Filter through the filter, measure results
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maxsample=0; minsample=1000000; totsample=0; samples=0;
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for (i=2048; i<8192; i++) {
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//waveout[i] = wavein[i];
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sample = abs(firfilter(wavein, i, 8192, count, coefficients));
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if (sample > maxsample) maxsample=sample;
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if (sample < minsample) minsample=sample;
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totsample += sample; samples++;
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}
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// Report results
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fprintf(stderr, "%5d %5d %5d %5d %f\n", freq, totsample/samples, maxsample, minsample, 10*log((totsample/samples)/6500.0));
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}
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}
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#endif
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