changed sync_decim to compare to threshold instead of skip vs noskip

works good for strong stations (carrierSNR>=40dB)

apps/ifft-RDS-decoder_hier-block.grc

@@ -2402,7 +2402,7 @@
     </param>
     <param>
       <key>log</key>
-      <value>False</value>
+      <value>log</value>
     </param>
     <param>
       <key>maxoutbuf</key>
@@ -2414,7 +2414,7 @@
     </param>
     <param>
       <key>threshold</key>
-      <value>0.25</value>
+      <value>1</value>
     </param>
     <param>
       <key>min_diff</key>

apps/read_fmdec.grc

@@ -1369,7 +1369,7 @@ class blk(gr.sync_block):  # other base classes are basic_block, decim_block, in
     </param>
     <param>
       <key>threshold</key>
-      <value>0.25</value>
+      <value>1</value>
     </param>
     <param>
       <key>min_diff</key>

lib/sync_decim_impl.cc

@@ -27,7 +27,7 @@
 #define DECIM 2
 #define lout log && std::cout
 //#define SYNC_COUNTER_MAX 5//higher value -> slower sync, less cpu load
-#define SYNC_COUNTER_MAX 7//higher value -> slower sync, less cpu load
+#define SYNC_COUNTER_MAX 200//higher value -> slower sync, less cpu load
 //#include <pmt.h>
 namespace gr {
   namespace multirds {
@@ -97,6 +97,7 @@ namespace gr {
                               gr_vector_const_void_star &input_items,
                               gr_vector_void_star &output_items)
         {
+          //if (noutput_items>8){
           const float *in = (const float *) input_items[0];
           float *out = (float *) output_items[0];
           if(outbit_counter>4000){
@@ -124,51 +125,67 @@ namespace gr {
             }
           }
           last_input=in[(noutput_items-1)*DECIM+1];//to use for next iteration of work
-          lout<<noutput_items<<std::endl;
+          //lout<<noutput_items<<std::endl;
           
           /*synchronize:*/
           if(mode==COPY and dosync_counter>=SYNC_COUNTER_MAX){
+            lout<<noutput_items<<std::endl;
 	    dosync_counter=0;
             float out_noskip;
             float out_skip;
             int skip_is_better_counter=0;
-            if (noutput_items>8)//TODO: what if there are never more than 9 outputs requested
+            if (noutput_items>4)//TODO: what if there are never more than 9 outputs requested
             {
-              for (int i = 0; i < noutput_items; i++) {
+              for (int i = 0; i < noutput_items; i++) {//TODO set max loop length -> cpu load
                 if(i==0){
                   out_skip=last_input-in[DECIM*i];}
                   else{
                     out_skip=in[DECIM*i-1]-in[DECIM*i];}
                     
                 out_noskip=in[DECIM*i]-in[DECIM*i+1];
-                if (std::abs(out_skip)>std::abs(out_noskip)){
+                
+                /*if (std::abs(out_skip)>std::abs(out_noskip)){
 		  skip_is_better_counter++;
                 }
                 else{
 		  skip_is_better_counter--;
+                }*/
+                if (std::abs(out_skip)>threshold){
+                  skip_is_better_counter++;
+                }
+                if (std::abs(out_noskip) >threshold){
+                  skip_is_better_counter--;
                 }
+                
                 //lout<<"state:"<< mode;
+                //lout<<"noutputs:"<<noutput_items;
+                
+                //lout<<"in:"<<in[DECIM*i];
                 //lout<<"\t,out_noskip:"<<out_noskip;
                 //lout<<"\t,out_skip:"<<out_skip<<std::endl;
                 
               }
               if (skip_is_better_counter>3){//2017-05-02 lowered from 6
-                mode=SKIP;
+  
                 pmt::pmt_t meta(pmt::from_long(4));
-                pmt::pmt_t data(pmt::from_long(mode));
+                pmt::pmt_t data(pmt::from_long(SKIP));
                 pmt::pmt_t pdu(pmt::cons(meta, data));  // make PDU: (metadata, data) pair
                 message_port_pub(pmt::mp("ctrl"), pdu);
+                mode=SKIP;
                 lout<<"switched to skip"<< std::endl;
               }
               else if (skip_is_better_counter<-3){
                 pmt::pmt_t meta(pmt::from_long(4));
-                pmt::pmt_t data(pmt::from_long(mode));
+                pmt::pmt_t data(pmt::from_long(NOSKIP));
                 pmt::pmt_t pdu(pmt::cons(meta, data));  // make PDU: (metadata, data) pair
                 message_port_pub(pmt::mp("ctrl"), pdu);
                 mode=NOSKIP;
                 lout<<"switched to noskip"<< std::endl;
               }
             }
+            else{//wait for longer input
+              dosync_counter=SYNC_COUNTER_MAX-2;
+            }
           }
 	  else if(mode==COPY){
 	      dosync_counter++;
@@ -177,6 +194,9 @@ namespace gr {
           // Tell runtime system how many output items we produced.
           outbit_counter+=noutput_items;
           return noutput_items;
+            
+          /*}
+          else{return 0;}*/
         }/*end of work*/
   } /* namespace multirds */
 } /* namespace gr */