diff --git a/demod/mod/demod_mod.c b/demod/mod/demod_mod.c
index d6d4533..8492d66 100644
--- a/demod/mod/demod_mod.c
+++ b/demod/mod/demod_mod.c
@@ -125,14 +125,14 @@ static int dft_window(dft_t *dft, int w) {
                     dft->win[n] = 1.0;
                     break;
             case 1: // Hann
-                    dft->win[n] = 0.5 * ( 1.0 - cos(2*M_PI*n/(float)(dft->N2-1)) );
+                    dft->win[n] = 0.5 * ( 1.0 - cos(_2PI*n/(float)(dft->N2-1)) );
                     break ;
             case 2: // Hamming
-                    dft->win[n] = 25/46.0 - (1.0 - 25/46.0)*cos(2*M_PI*n / (float)(dft->N2-1));
+                    dft->win[n] = 25/46.0 - (1.0 - 25/46.0)*cos(_2PI*n / (float)(dft->N2-1));
                     break ;
             case 3: // Blackmann
                     dft->win[n] =  7938/18608.0
-                                 - 9240/18608.0*cos(2*M_PI*n / (float)(dft->N2-1))
+                                 - 9240/18608.0*cos(_2PI*n / (float)(dft->N2-1))
                                  + 1430/18608.0*cos(4*M_PI*n / (float)(dft->N2-1));
                     break ;
         }
@@ -310,7 +310,7 @@ static int findstr(char *buff, char *str, int pos) {
     return i;
 }
 
-float read_wav_header(pcm_t *pcm, FILE *fp) {
+int read_wav_header(pcm_t *pcm, FILE *fp) {
     char txt[4+1] = "\0\0\0\0";
     unsigned char dat[4];
     int byte, p=0;
@@ -567,7 +567,7 @@ static int lowpass_init(float f, int taps, float **pws) {
     ws = (float*)calloc( 2*taps+1, sizeof(float)); if (ws == NULL) return -1;
 
     for (n = 0; n < taps; n++) {
-        w[n] = 7938/18608.0 - 9240/18608.0*cos(2*M_PI*n/(taps-1)) + 1430/18608.0*cos(4*M_PI*n/(taps-1)); // Blackmann
+        w[n] = 7938/18608.0 - 9240/18608.0*cos(_2PI*n/(taps-1)) + 1430/18608.0*cos(4*M_PI*n/(taps-1)); // Blackmann
         h[n] = 2*f*sinc(2*f*(n-(taps-1)/2));
         ws[n] = w[n]*h[n];
         norm += ws[n]; // 1-norm
@@ -600,7 +600,7 @@ static int lowpass_update(float f, int taps, float *ws) {
     w = (double*)calloc( taps+1, sizeof(double)); if (w == NULL) return -1;
 
     for (n = 0; n < taps; n++) {
-        w[n] = 7938/18608.0 - 9240/18608.0*cos(2*M_PI*n/(taps-1)) + 1430/18608.0*cos(4*M_PI*n/(taps-1)); // Blackmann
+        w[n] = 7938/18608.0 - 9240/18608.0*cos(_2PI*n/(taps-1)) + 1430/18608.0*cos(4*M_PI*n/(taps-1)); // Blackmann
         h[n] = 2*f*sinc(2*f*(n-(taps-1)/2));
         ws[n] = w[n]*h[n];
         norm += ws[n]; // 1-norm
@@ -675,7 +675,7 @@ int f32buf_sample(dsp_t *dsp, int inv) {
                 if (dsp->opt_nolut) {
                     double _s_base = (double)(dsp->sample_in*dsp->decM+j); // dsp->sample_dec
                     double f0 = dsp->xlt_fq*_s_base - dsp->Df*_s_base/(double)dsp->sr_base;
-                    z = dsp->decMbuf[j] * cexp(f0*2*M_PI*I);
+                    z = dsp->decMbuf[j] * cexp(f0*_2PI*I);
                 }
                 else {
                     z = dsp->decMbuf[j] * dsp->ex[dsp->sample_dec % dsp->lut_len];
@@ -694,7 +694,7 @@ int f32buf_sample(dsp_t *dsp, int inv) {
 
         if (dsp->opt_dc && !dsp->opt_nolut)
         {
-            z *= cexp(-t*2*M_PI*dsp->Df*I);
+            z *= cexp(-t*_2PI*dsp->Df*I);
         }
 
 
@@ -717,8 +717,8 @@ int f32buf_sample(dsp_t *dsp, int inv) {
             if (dsp->opt_iq >= 2) {
                 double xbit = 0.0;
                 //float complex xi = cexp(+I*M_PI*dsp->h/dsp->sps);
-                double f1 = -dsp->h*dsp->sr/(2.0*dsp->sps);
-                double f2 = -f1;
+                //double f1 = -dsp->h*dsp->sr/(2.0*dsp->sps);
+                //double f2 = -f1;
 
                 float complex X0 = 0;
                 float complex X  = 0;
@@ -730,13 +730,13 @@ int f32buf_sample(dsp_t *dsp, int inv) {
                 z0 = dsp->rot_iqbuf[(dsp->sample_in-n + dsp->N_IQBUF) % dsp->N_IQBUF];
 
                 // f1
-                X0 = z0 * cexp(-tn*2*M_PI*f1*I); // alt
-                X  = z  * cexp(-t *2*M_PI*f1*I); // neu
+                X0 = z0 * cexp(-tn*dsp->iw1); // alt
+                X  = z  * cexp(-t *dsp->iw1); // neu
                 dsp->F1sum +=  X - X0;
 
                 // f2
-                X0 = z0 * cexp(-tn*2*M_PI*f2*I); // alt
-                X  = z  * cexp(-t *2*M_PI*f2*I); // neu
+                X0 = z0 * cexp(-tn*dsp->iw2); // alt
+                X  = z  * cexp(-t *dsp->iw2); // neu
                 dsp->F2sum +=  X - X0;
 
                 xbit = cabs(dsp->F2sum) - cabs(dsp->F1sum);
@@ -746,8 +746,8 @@ int f32buf_sample(dsp_t *dsp, int inv) {
             else if (0 && dsp->opt_iq == 4) {
                 double xbit = 0.0;
                 //float complex xi = cexp(+I*M_PI*dsp->h/dsp->sps);
-                double f1 = -dsp->h*dsp->sr/(2*dsp->sps);
-                double f2 = -f1;
+                //double f1 = -dsp->h*dsp->sr/(2*dsp->sps);
+                //double f2 = -f1;
 
                 float complex X1 = 0;
                 float complex X2 = 0;
@@ -758,8 +758,8 @@ int f32buf_sample(dsp_t *dsp, int inv) {
                     n--;
                     t = -n / (double)dsp->sr;
                     z = dsp->rot_iqbuf[(dsp->sample_in - n + dsp->N_IQBUF) % dsp->N_IQBUF];  // +1
-                    X1 += z*cexp(-t*2*M_PI*f1*I);
-                    X2 += z*cexp(-t*2*M_PI*f2*I);
+                    X1 += z*cexp(-t*dsp->iw1);
+                    X2 += z*cexp(-t*dsp->iw2);
                 }
 
                 xbit = cabs(X2) - cabs(X1);
@@ -1145,7 +1145,7 @@ int init_buffers(dsp_t *dsp) {
     int i, pos;
     float b0, b1, b2, b, t;
     float normMatch;
-    double sigma = sqrt(log(2)) / (2*M_PI*dsp->BT);
+    double sigma = sqrt(log(2)) / (_2PI*dsp->BT);
 
     int p2 = 1;
     int K, L, M;
@@ -1226,7 +1226,7 @@ int init_buffers(dsp_t *dsp) {
             if (dsp->ex == NULL) return -1;
             for (n = 0; n < dsp->lut_len; n++) {
                 t = f0*(double)n;
-                dsp->ex[n] = cexp(t*2*M_PI*I);
+                dsp->ex[n] = cexp(t*_2PI*I);
             }
         }
 
@@ -1397,6 +1397,14 @@ int init_buffers(dsp_t *dsp) {
     dsp->fm_buffer = (float *)calloc( M+1, sizeof(float));  if (dsp->fm_buffer == NULL) return -1; // dsp->bufs[]
 
 
+    if (dsp->opt_iq)
+    {
+        double f1 = -dsp->h*dsp->sr/(2.0*dsp->sps);
+        double f2 = -f1;
+        dsp->iw1 = _2PI*I*f1;
+        dsp->iw2 = _2PI*I*f2;
+    }
+
     return K;
 }
 
@@ -1488,8 +1496,8 @@ int find_header(dsp_t *dsp, float thres, int hdmax, int bitofs, int opt_dc) {
                         double diffDf = dsp->dDf*0.6; //0.4
                         if (1 && dsp->opt_iq >= 2) {
                             // update rot_iqbuf, F1sum, F2sum
-                            double f1 = -dsp->h*dsp->sr/(2*dsp->sps);
-                            double f2 = -f1;
+                            //double f1 = -dsp->h*dsp->sr/(2*dsp->sps);
+                            //double f2 = -f1;
                             float complex X1 = 0;
                             float complex X2 = 0;
                             float complex _z = 0;
@@ -1498,12 +1506,12 @@ int find_header(dsp_t *dsp, float thres, int hdmax, int bitofs, int opt_dc) {
                             {
                                 // update rot_iqbuf
                                 double _tn = (dsp->sample_in - _n) / (double)dsp->sr;
-                                dsp->rot_iqbuf[(dsp->sample_in - _n + dsp->N_IQBUF) % dsp->N_IQBUF] *= cexp(-_tn*2*M_PI*diffDf*I);
+                                dsp->rot_iqbuf[(dsp->sample_in - _n + dsp->N_IQBUF) % dsp->N_IQBUF] *= cexp(-_tn*_2PI*diffDf*I);
                                 //
                                 //update/reset F1sum, F2sum
                                 _z = dsp->rot_iqbuf[(dsp->sample_in - _n + dsp->N_IQBUF) % dsp->N_IQBUF];
-                                X1 += _z*cexp(-_tn*2*M_PI*f1*I);
-                                X2 += _z*cexp(-_tn*2*M_PI*f2*I);
+                                X1 += _z*cexp(-_tn*dsp->iw1);
+                                X2 += _z*cexp(-_tn*dsp->iw2);
                                 _n--;
                             }
                             dsp->F1sum = X1;
@@ -1549,7 +1557,7 @@ int find_header(dsp_t *dsp, float thres, int hdmax, int bitofs, int opt_dc) {
 #else
 // external FSK demod: read float32 soft symbols
 
-float read_wav_header(pcm_t *pcm, FILE *fp) {}
+int read_wav_header(pcm_t *pcm, FILE *fp) {}
 int f32buf_sample(dsp_t *dsp, int inv) {}
 int read_slbit(dsp_t *dsp, int *bit, int inv, int ofs, int pos, float l, int spike) {}
 int read_softbit(dsp_t *dsp, hsbit_t *shb, int inv, int ofs, int pos, float l, int spike) {}
diff --git a/demod/mod/demod_mod.h b/demod/mod/demod_mod.h
index 5fb4899..ef936f4 100644
--- a/demod/mod/demod_mod.h
+++ b/demod/mod/demod_mod.h
@@ -6,6 +6,8 @@
 #ifndef M_PI
     #define M_PI  (3.1415926535897932384626433832795)
 #endif
+#define _2PI  (6.2831853071795864769252867665590)
+
 
 #define LP_IQ    1
 #define LP_FM    2
@@ -83,6 +85,10 @@ typedef struct {
     float complex *rot_iqbuf;
     float complex F1sum;
     float complex F2sum;
+    //
+    double complex iw1;
+    double complex iw2;
+
 
     //
     char *rawbits;
@@ -169,7 +175,7 @@ typedef struct {
 } hdb_t;
 
 
-float read_wav_header(pcm_t *, FILE *);
+int read_wav_header(pcm_t *, FILE *);
 int f32buf_sample(dsp_t *, int);
 int read_slbit(dsp_t *, int*, int, int, int, float, int);
 int read_softbit(dsp_t *, hsbit_t *, int, int, int, float, int);