IQ baseband decode: samplecount overflow

demod/mod/demod_mod.c

@@ -381,7 +381,7 @@ static int get_SNR(dsp_t *dsp) {
 }
 
 
-static int res = 1; // 1..10 Hz, exp_lut resolution
+static ui32_t res = 1; // 1..10 Hz, exp_lut resolution
 static float *ws_dec;
 
 static double sinc(double x) {
@@ -400,9 +400,9 @@ static int decimate_init(int taps, float f) {
 
     if ( taps < 1 ) taps = 1;
 
-    h = (double*)calloc( taps+1, sizeof(double));
-    w = (double*)calloc( taps+1, sizeof(double));
-    ws_dec = (float*)calloc( taps+1, sizeof(float));
+    h = (double*)calloc( taps+1, sizeof(double)); if (h == NULL) return -1;
+    w = (double*)calloc( taps+1, sizeof(double)); if (w == NULL) return -1;
+    ws_dec = (float*)calloc( taps+1, sizeof(float)); if (ws_dec == 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
@@ -420,8 +420,8 @@ static int decimate_init(int taps, float f) {
     return taps;
 }
 
-static float complex lowpass(float complex buffer[], int sample, int M) {
-    int n;
+static float complex lowpass(float complex buffer[], ui32_t sample, ui32_t M) {
+    ui32_t n;
     double complex w = 0;
     for (n = 0; n < M; n++) {
         w += buffer[(sample+n+1)%M]*ws_dec[M-1-n];
@@ -441,11 +441,13 @@ int f32buf_sample(dsp_t *dsp, int inv) {
     if (dsp->opt_iq) {
 
         if (dsp->opt_iq == 5) {
+            ui32_t s_reset = dsp->dectaps*dsp->sr_base; // dsp->sr_base % res == 0
             int j;
             if ( f32read_cblock(dsp) < dsp->decM ) return EOF;
             for (j = 0; j < dsp->decM; j++) {
                 dsp->decXbuffer[dsp->sample_dec % dsp->dectaps] = dsp->decMbuf[j] * dsp->ex[dsp->sample_dec % (dsp->sr_base/res)];
                 dsp->sample_dec += 1;
+                if (dsp->sample_dec == s_reset) dsp->sample_dec = 0;
             }
             z = lowpass(dsp->decXbuffer, dsp->sample_dec, dsp->dectaps);
         }
@@ -774,7 +776,9 @@ int init_buffers(dsp_t *dsp) {
         t_bw /= sr_base;
         taps = 4.0/t_bw; if (taps%2==0) taps++;
 
-        dsp->dectaps = decimate_init(taps, f_lp);
+        taps = decimate_init(taps, f_lp);
+        if (taps < 0) return -1;
+        dsp->dectaps = (ui32_t)taps;
 
         dsp->sr_base = sr_base;
         dsp->sr = IF_sr; // sr_base/decM

demod/mod/demod_mod.h

@@ -92,13 +92,13 @@ typedef struct {
     double V_signal;
     double SNRdB;
 
-    int sr_base;
     int decM;
-    int dectaps;
+    ui32_t sr_base;
+    ui32_t dectaps;
+    ui32_t sample_dec;
     float complex *decXbuffer;
     float complex *decMbuf;
     float complex *ex; // exp_lut
-    ui32_t sample_dec;
     double xlt_fq;
 
 } dsp_t;