New way to handle arbitrary resampler. Now featuring lower noise!

3 files changed, 55 insertions, 37 deletions

diff --git a/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.cc b/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.cc
index d00ba6739..d4b14c594 100644
--- a/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.cc
+++ b/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.cc
@@ -59,24 +59,26 @@ gr_pfb_arb_resampler_ccf::gr_pfb_arb_resampler_ccf (float rate,
   d_dec_rate = (unsigned int)floor(d_int_rate/rate);
   d_flt_rate = (d_int_rate/rate) - d_dec_rate;
 
-  // The accumulator keeps track of overflow to increment the stride correctly.
-  d_acc = 0;
-
   // Store the last filter between calls to work
   d_last_filter = 0;
 
   d_start_index = 0;
   
   d_filters = std::vector<gr_fir_ccf*>(d_int_rate);
+  d_diff_filters = std::vector<gr_fir_ccf*>(d_int_rate);
 
   // Create an FIR filter for each channel and zero out the taps
   std::vector<float> vtaps(0, d_int_rate);
-  for(unsigned int i = 0; i < d_int_rate; i++) {
+  for(int i = 0; i < d_int_rate; i++) {
     d_filters[i] = gr_fir_util::create_gr_fir_ccf(vtaps);
+    d_diff_filters[i] = gr_fir_util::create_gr_fir_ccf(vtaps);
   }
 
   // Now, actually set the filters' taps
-  set_taps(taps);
+  std::vector<float> dtaps;
+  create_diff_taps(taps, dtaps);
+  set_taps(taps, d_taps, d_filters);
+  set_taps(dtaps, d_dtaps, d_diff_filters);
 }
 
 gr_pfb_arb_resampler_ccf::~gr_pfb_arb_resampler_ccf ()
@@ -87,20 +89,22 @@ gr_pfb_arb_resampler_ccf::~gr_pfb_arb_resampler_ccf ()
 }
 
 void
-gr_pfb_arb_resampler_ccf::set_taps (const std::vector<float> &taps)
+gr_pfb_arb_resampler_ccf::set_taps (const std::vector<float> &newtaps,
+				    std::vector< std::vector<float> > &ourtaps,
+				    std::vector<gr_fir_ccf*> &ourfilter)
 {
-  unsigned int i,j;
+  int i,j;
 
-  unsigned int ntaps = taps.size();
+  unsigned int ntaps = newtaps.size();
   d_taps_per_filter = (unsigned int)ceil((double)ntaps/(double)d_int_rate);
 
   // Create d_numchan vectors to store each channel's taps
-  d_taps.resize(d_int_rate);
-
+  ourtaps.resize(d_int_rate);
+  
   // Make a vector of the taps plus fill it out with 0's to fill
   // each polyphase filter with exactly d_taps_per_filter
   std::vector<float> tmp_taps;
-  tmp_taps = taps;
+  tmp_taps = newtaps;
   while((float)(tmp_taps.size()) < d_int_rate*d_taps_per_filter) {
     tmp_taps.push_back(0.0);
   }
@@ -108,22 +112,45 @@ gr_pfb_arb_resampler_ccf::set_taps (const std::vector<float> &taps)
   // Partition the filter
   for(i = 0; i < d_int_rate; i++) {
     // Each channel uses all d_taps_per_filter with 0's if not enough taps to fill out
-    d_taps[i] = std::vector<float>(d_taps_per_filter, 0);
+    ourtaps[d_int_rate-1-i] = std::vector<float>(d_taps_per_filter, 0);
     for(j = 0; j < d_taps_per_filter; j++) {
-      d_taps[i][j] = tmp_taps[i + j*d_int_rate];  // add taps to channels in reverse order
+      ourtaps[d_int_rate - 1 - i][j] = tmp_taps[i + j*d_int_rate];
     }
     
     // Build a filter for each channel and add it's taps to it
-    d_filters[i]->set_taps(d_taps[i]);
+    ourfilter[i]->set_taps(ourtaps[d_int_rate-1-i]);
   }
 
   // Set the history to ensure enough input items for each filter
-  set_history (d_taps_per_filter);
+  set_history (d_taps_per_filter + 1);
 
   d_updated = true;
 }
 
 void
+gr_pfb_arb_resampler_ccf::create_diff_taps(const std::vector<float> &newtaps,
+					   std::vector<float> &difftaps)
+{
+  float maxtap = 1e-20;
+  difftaps.clear();
+  difftaps.push_back(0); //newtaps[0]);
+  for(unsigned int i = 1; i < newtaps.size()-1; i++) {
+    float tap = newtaps[i+1] - newtaps[i-1];
+    difftaps.push_back(tap);
+    if(tap > maxtap) {
+      maxtap = tap;
+    }
+  }
+  difftaps.push_back(0);//-newtaps[newtaps.size()-1]);
+
+  // Scale the differential taps; helps scale error term to better update state
+  // FIXME: should this be scaled this way or use the same gain as the taps?
+  for(unsigned int i = 0; i < difftaps.size(); i++) {
+    difftaps[i] /= maxtap;
+  }
+}
+
+void
 gr_pfb_arb_resampler_ccf::print_taps()
 {
   unsigned int i, j;
@@ -163,27 +190,12 @@ gr_pfb_arb_resampler_ccf::general_work (int noutput_items,
     while((j < d_int_rate) && (i < noutput_items)) {
       // Take the current filter output
       o0 = d_filters[j]->filter(&in[count]);
+      o1 = d_diff_filters[j]->filter(&in[count]);
 
-      // Take the next filter output; wrap around to 0 if necessary
-      if(j+1 == d_int_rate)
-	// Use the sample of the next input item through the first filter
-	o1 = d_filters[0]->filter(&in[count+1]);
-      else {
-	// Use the sample from the current input item through the nex filter
-	o1 = d_filters[j+1]->filter(&in[count]);
-      }
-
-      //out[i] = o0;                     // nearest-neighbor approach
-      out[i] = o0 + (o1 - o0)*d_acc;     // linearly interpolate between samples
+      out[i] = o0 + o1*d_flt_rate;     // linearly interpolate between samples
       i++;
       
-      // Accumulate the position in the stream for the interpolated point.
-      // If it goes above 1, roll around to zero and increment the stride
-      // length this time by the decimation rate plus 1 for the increment
-      // due to the acculated position.
-      d_acc += d_flt_rate;
-      j += d_dec_rate + (int)floor(d_acc);
-      d_acc = fmodf(d_acc, 1.0);
+      j += d_dec_rate;
     }
     if(i < noutput_items) {              // keep state for next entry
       float ss = (int)(j / d_int_rate);  // number of items to skip ahead by
diff --git a/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.h b/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.h
index bc5b91a5e..531e9726f 100644
--- a/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.h
+++ b/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.h
@@ -112,11 +112,12 @@ class gr_pfb_arb_resampler_ccf : public gr_block
 								      unsigned int filter_size);
 
   std::vector<gr_fir_ccf*> d_filters;
+  std::vector<gr_fir_ccf*> d_diff_filters;
   std::vector< std::vector<float> > d_taps;
+  std::vector< std::vector<float> > d_dtaps;
   unsigned int             d_int_rate;          // the number of filters (interpolation rate)
   unsigned int             d_dec_rate;          // the stride through the filters (decimation rate)
   float                    d_flt_rate;          // residual rate for the linear interpolation
-  float                    d_acc;
   unsigned int             d_last_filter;
   int                      d_start_index;
   unsigned int             d_taps_per_filter;
@@ -134,16 +135,21 @@ class gr_pfb_arb_resampler_ccf : public gr_block
   gr_pfb_arb_resampler_ccf (float rate, 
 			    const std::vector<float> &taps,
 			    unsigned int filter_size);
+
+  void create_diff_taps(const std::vector<float> &newtaps,
+			std::vector<float> &difftaps);
   
 public:
   ~gr_pfb_arb_resampler_ccf ();
-  
+ 
   /*!
    * Resets the filterbank's filter taps with the new prototype filter
    * \param taps    (vector/list of floats) The prototype filter to populate the filterbank. The taps
    *                                        should be generated at the interpolated sampling rate.
    */
-  void set_taps (const std::vector<float> &taps);
+  void set_taps (const std::vector<float> &newtaps,
+		 std::vector< std::vector<float> > &ourtaps,
+		 std::vector<gr_fir_ccf*> &ourfilter);
 
   /*!
    * Print all of the filterbank taps to screen.
diff --git a/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.i b/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.i
index e365e0314..4f07af861 100644
--- a/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.i
+++ b/gnuradio-core/src/lib/filter/gr_pfb_arb_resampler_ccf.i
@@ -36,6 +36,6 @@ class gr_pfb_arb_resampler_ccf : public gr_block
  public:
   ~gr_pfb_arb_resampler_ccf ();
 
-  void set_taps (const std::vector<float> &taps);
+  //void set_taps (const std::vector<float> &taps);
   void print_taps();
 };