95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include "kiss_fft.h"
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#include "kiss_fftr.h"
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#include <limits.h>
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static
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double two_tone_test( int nfft, int bin1,int bin2)
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{
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kiss_fftr_cfg cfg = NULL;
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kiss_fft_cpx *kout = NULL;
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kiss_fft_scalar *tbuf = NULL;
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int i;
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double f1 = bin1*2*M_PI/nfft;
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double f2 = bin2*2*M_PI/nfft;
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double sigpow=0;
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double noisepow=0;
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#if FIXED_POINT==32
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long maxrange = LONG_MAX;
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#else
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long maxrange = SHRT_MAX;/* works fine for float too*/
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#endif
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cfg = kiss_fftr_alloc(nfft , 0, NULL, NULL);
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tbuf = KISS_FFT_MALLOC(nfft * sizeof(kiss_fft_scalar));
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kout = KISS_FFT_MALLOC(nfft * sizeof(kiss_fft_cpx));
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/* generate a signal with two tones*/
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for (i = 0; i < nfft; i++) {
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#ifdef USE_SIMD
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tbuf[i] = _mm_set1_ps( (maxrange>>1)*cos(f1*i)
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+ (maxrange>>1)*cos(f2*i) );
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#else
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tbuf[i] = (maxrange>>1)*cos(f1*i)
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+ (maxrange>>1)*cos(f2*i);
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#endif
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}
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kiss_fftr(cfg, tbuf, kout);
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for (i=0;i < (nfft/2+1);++i) {
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#ifdef USE_SIMD
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double tmpr = (double)*(float*)&kout[i].r / (double)maxrange;
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double tmpi = (double)*(float*)&kout[i].i / (double)maxrange;
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#else
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double tmpr = (double)kout[i].r / (double)maxrange;
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double tmpi = (double)kout[i].i / (double)maxrange;
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#endif
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double mag2 = tmpr*tmpr + tmpi*tmpi;
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if (i!=0 && i!= nfft/2)
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mag2 *= 2; /* all bins except DC and Nyquist have symmetric counterparts implied*/
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/* if there is power in one of the expected bins, it is signal, otherwise noise*/
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if ( i!=bin1 && i != bin2 )
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noisepow += mag2;
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else
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sigpow += mag2;
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}
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kiss_fft_cleanup();
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/*printf("TEST %d,%d,%d noise @ %fdB\n",nfft,bin1,bin2,10*log10(noisepow/sigpow +1e-30) );*/
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return 10*log10(sigpow/(noisepow+1e-50) );
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}
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int main(int argc,char ** argv)
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{
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int nfft = 4*2*2*3*5;
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if (argc>1) nfft = atoi(argv[1]);
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int i,j;
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double minsnr = 500;
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double maxsnr = -500;
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double snr;
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for (i=0;i<nfft/2;i+= (nfft>>4)+1) {
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for (j=i;j<nfft/2;j+=(nfft>>4)+7) {
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snr = two_tone_test(nfft,i,j);
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if (snr<minsnr) {
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minsnr=snr;
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}
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if (snr>maxsnr) {
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maxsnr=snr;
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}
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}
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}
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snr = two_tone_test(nfft,nfft/2,nfft/2);
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if (snr<minsnr) minsnr=snr;
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if (snr>maxsnr) maxsnr=snr;
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printf("TwoToneTest: snr ranges from %ddB to %ddB\n",(int)minsnr,(int)maxsnr);
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printf("sizeof(kiss_fft_scalar) = %d\n",(int)sizeof(kiss_fft_scalar) );
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return 0;
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}
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