Change the quadrature demod filter to sync block

Seems that there is a probleb with general blocks and the history, so
the filter cannot act as valve. However, it produces zeros, in the
presence of noise.

grc/satnogs_quad_demod_filter_ff.xml

@@ -8,9 +8,16 @@
   <param>
     <name>Threshold</name>
     <key>thresh</key>
-    <value>math.pi</value>
+    <value>1.0</value>
     <type>real</type>
   </param>
+  
+  <param>
+    <name>Window Size</name>
+    <key>win</key>
+    <value>80</value>
+    <type>int</type>
+  </param>
 
   <!-- Make one 'sink' node per input. Sub-nodes:
        * name (an identifier for the GUI)

include/satnogs/quad_demod_filter_ff.h

@@ -23,7 +23,7 @@
 #define INCLUDED_SATNOGS_QUAD_DEMOD_FILTER_FF_H
 
 #include <satnogs/api.h>
-#include <gnuradio/block.h>
+#include <gnuradio/sync_block.h>
 
 namespace gr {
   namespace satnogs {
@@ -50,7 +50,7 @@ namespace gr {
      * \ingroup satnogs
      *
      */
-    class SATNOGS_API quad_demod_filter_ff : virtual public gr::block
+    class SATNOGS_API quad_demod_filter_ff : virtual public gr::sync_block
     {
      public:
       typedef boost::shared_ptr<quad_demod_filter_ff> sptr;
@@ -58,8 +58,8 @@ namespace gr {
 
       /**
        * Creates a Quadrature Demodulate filter. The block will output samples
-       * only in signal presence acting as a valve to reduce false alarms of
+       * only in signal presence acting as a "valve" to reduce false alarms of
-       * the FSK decoders.
+       * the FSK decoders. In case of no signal, zero samples are produced.
        *
        * @param gain this MUST be the gain set on the quadrature demodulate
        * gain or an appropriate value if the amplitude of the quadrature

lib/quad_demod_filter_ff_impl.cc

@@ -40,9 +40,9 @@ namespace gr {
      */
     quad_demod_filter_ff_impl::quad_demod_filter_ff_impl (float gain,
                                                           int window) :
-            gr::block ("quad_demod_filter_ff",
+            gr::sync_block ("quad_demod_filter_ff",
-                       gr::io_signature::make (1, 1, sizeof(float)),
+                            gr::io_signature::make (1, 1, sizeof(float)),
-                       gr::io_signature::make (1, 1, sizeof(float))),
+                            gr::io_signature::make (1, 1, sizeof(float))),
             d_gain (gain),
             d_norm (1.0f / window),
             d_win (window),
@@ -53,7 +53,7 @@ namespace gr {
       if(window < 1) {
         throw std::invalid_argument ("Window must be a positive");
       }
-      set_history (2 * window);
+      set_history (window);
     }
 
     /*
@@ -86,15 +86,12 @@ namespace gr {
     }
 
     int
-    quad_demod_filter_ff_impl::general_work (
+    quad_demod_filter_ff_impl::work (int noutput_items,
-        int noutput_items, gr_vector_int &ninput_items,
+                                     gr_vector_const_void_star &input_items,
-        gr_vector_const_void_star &input_items,
+                                     gr_vector_void_star &output_items)
-        gr_vector_void_star &output_items)
     {
       const float *in = (const float *) input_items[0];
       float *out = (float *) output_items[0];
-      int available = std::min(ninput_items[0], noutput_items);
-      int produced = 0;
       float m;
       float m_sq;
       float snr;
@@ -102,9 +99,9 @@ namespace gr {
       float in_new;
 
       float diff;
-      for(int i = 0; i < available; i++) {
+      for (int i = 0; i < noutput_items; i++) {
-        in_old = std::abs(in[i + d_win]);
+        in_old = std::abs (in[i]);
-        in_new = std::abs(in[i + 2*d_win - 1]);
+        in_new = std::abs (in[i + d_win - 1]);
         d_sum -= in_old;
         d_sum += in_new;
         d_sum_sq -= (in_old * in_old);
@@ -112,7 +109,7 @@ namespace gr {
 
         m = (d_sum * d_norm);
         m_sq = (d_sum_sq * d_norm);
-        snr = m  * inv_sqrt(m_sq - m*m);
+        snr = m * inv_sqrt (m_sq - m * m);
 
         /*
          * If the SNR is high enough start passing the data to the output.
@@ -120,19 +117,21 @@ namespace gr {
          * from the buffered and let a window of samples to pass after the
          * trigger is off
          */
-        if(snr > d_gain * 1.8) {
+        if (snr > d_gain * 1.8) {
-          d_remaining = 2*d_win;
+          d_remaining = 2 * d_win;
         }
 
-        if(d_remaining) {
+        if (d_remaining) {
-          out[produced++] = in[i];
+          out[i] = in[i];
           d_remaining--;
         }
+        else {
+          out[i] = 0.0f;
+        }
       }
 
       // Tell runtime system how many output items we produced.
-      consume_each(available);
+      return noutput_items;
-      return produced;
     }
 
   } /* namespace satnogs */

lib/quad_demod_filter_ff_impl.h

@@ -40,11 +40,9 @@ namespace gr {
       quad_demod_filter_ff_impl(float gain, int window);
       ~quad_demod_filter_ff_impl();
 
-      // Where all the action really happens
       int
-      general_work (int noutput_items, gr_vector_int &ninput_items,
+      work (int noutput_items, gr_vector_const_void_star &input_items,
-                    gr_vector_const_void_star &input_items,
+            gr_vector_void_star &output_items);
-                    gr_vector_void_star &output_items);
     };
 
   } // namespace satnogs