pick the peak frequency from a stereo input

test/freqpeak.c

@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <string.h>
+#include <memory.h>
+#include <malloc.h>
+#include <stdio.h>
+#include <math.h>
+#include "kiss_fft.h"
+
+#define NFFT 1024
+int main(int argc, char ** argv)
+{
+    int k;
+    void * st;
+    float fs=44100;
+
+    short sampsin[2*NFFT];
+    float lmag2[NFFT/2];
+    float rmag2[NFFT/2];
+    int peakr=0,peakl=0;
+    int removedc=1;
+
+    kiss_fft_cpx cbuf[NFFT];
+    int nbufs=0;
+
+    st = kiss_fft_alloc(NFFT,0);
+
+    memset( lmag2 , 0 , sizeof(lmag2) );
+    memset( rmag2 , 0 , sizeof(rmag2) );
+
+    while ( fread( sampsin , sizeof(short) * 2*NFFT, 1 , stdin ) == 1 ) {
+
+        //perform two ffts in parallel by packing the left&right channels into the real and imaginary
+        for (k=0;k<NFFT;++k) {
+            cbuf[k].r = sampsin[2*k];
+            cbuf[k].i = sampsin[2*k+1];
+        }
+
+        if (removedc) {
+            float dcr=0,dci=0;
+            for (k=0;k<NFFT;++k){
+                dcr += cbuf[k].r;
+                dci += cbuf[k].i;
+            }
+            dcr /= NFFT;
+            dci /= NFFT;
+
+            for (k=0;k<NFFT;++k) {
+                cbuf[k].r -= dcr;
+                cbuf[k].i -= dci;
+            }
+        }
+
+        // perform the fft on the L+R packed buffer
+        kiss_fft( st , cbuf );
+
+        // get the half-symmetric FFTs for the Left and Right Channels
+        for (k=0;k<NFFT/2;++k) {
+            int k2 = (NFFT-k)%NFFT;
+            kiss_fft_cpx r,l;
+
+            r.r = (cbuf[k].r + cbuf[k2].r) * 0.5;
+            r.i = (cbuf[k].i - cbuf[k2].i) * 0.5;
+
+            l.r = (cbuf[k].i + cbuf[k2].i) * 0.5;
+            l.i = (cbuf[k].r - cbuf[k2].r) * 0.5;
+
+            rmag2[k] += r.r * r.r + r.i * r.i;
+            lmag2[k] += l.r * l.r + l.i * l.i;
+        }
+        ++nbufs;
+    }
+    free(st);
+
+    for (k=0;k<NFFT/2;++k) {
+        if (rmag2[peakr] < rmag2[k])
+            peakr = k;
+        if (lmag2[peakl] < lmag2[k])
+            peakl = k;
+    }
+
+    printf("%d buffers\n",nbufs);
+
+    printf("peak frequency R:%.3fdB @ %.1f Hz\n",10*log10(rmag2[peakr]) , peakr*fs/NFFT);
+    printf("               L:%.3fdB @ %.1f Hz\n",10*log10(lmag2[peakl]) , peakl*fs/NFFT);
+
+    return 0;
+}