[Commit-gnuradio] [gnuradio] 04/09: Fixed an algorithmic problem with the Viterbi decoder

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commit dbbc0687b7323c86eb2b1c2d7524ff212bbd64d8
Author: Andrew F. Davis <address@hidden>
Date:   Sat Jun 28 19:03:21 2014 -0400

    Fixed an algorithmic problem with the Viterbi decoder
---
 gr-dtv/lib/atsc_rs_decoder_impl.cc      | 30 ++++++++++------------
 gr-dtv/lib/atsc_rs_decoder_impl.h       |  1 -
 gr-dtv/lib/atsc_single_viterbi.cc       | 44 +++++++++++++++------------------
 gr-dtv/lib/atsc_single_viterbi.h        | 11 +++++----
 gr-dtv/lib/atsc_viterbi_decoder_impl.cc | 32 ++++++++++++------------
 gr-dtv/lib/atsc_viterbi_decoder_impl.h  |  3 +--
 gr-dtv/python/dtv/atsc_rx.py            |  2 +-
 7 files changed, 57 insertions(+), 66 deletions(-)

diff --git a/gr-dtv/lib/atsc_rs_decoder_impl.cc 
b/gr-dtv/lib/atsc_rs_decoder_impl.cc
index cd9588d..7fb6541 100644
--- a/gr-dtv/lib/atsc_rs_decoder_impl.cc
+++ b/gr-dtv/lib/atsc_rs_decoder_impl.cc
@@ -59,7 +59,6 @@ namespace gr {
       nerrors_corrrected_count = 0;
       bad_packet_count = 0;
       total_packets = 0;
-      reset_counter = 0;
     }
 
     int atsc_rs_decoder_impl::decode (atsc_mpeg_packet_no_sync &out, const 
atsc_mpeg_packet_rs_encoded &in)
@@ -107,23 +106,20 @@ namespace gr {
           bad_packet_count++;
         else
           nerrors_corrrected_count += nerrors_corrrected;
-      }
 
-      total_packets += noutput_items;
-      reset_counter++;
-
-      if (reset_counter > 100) {
-        // FIXME: convert to logger
-        std::cout << "Error rate: "
-                  << (float)nerrors_corrrected_count/total_packets
-                  << "\tPacket error rate: "
-                  << (float)bad_packet_count/total_packets
-                  << std::endl;
-
-        nerrors_corrrected_count = 0;
-        bad_packet_count = 0;
-        total_packets = 0;
-        reset_counter = 0;
+       total_packets++;
+        if (total_packets > 1000) {
+          // FIXME: convert to logger
+          std::cout << "Error rate: "
+                    << (float)nerrors_corrrected_count/total_packets
+                    << "\tPacket error rate: "
+                    << (float)bad_packet_count/total_packets
+                    << std::endl;
+
+          nerrors_corrrected_count = 0;
+          bad_packet_count = 0;
+          total_packets = 0;
+        }
       }
 
       return noutput_items;
diff --git a/gr-dtv/lib/atsc_rs_decoder_impl.h 
b/gr-dtv/lib/atsc_rs_decoder_impl.h
index 691d619..5746012 100644
--- a/gr-dtv/lib/atsc_rs_decoder_impl.h
+++ b/gr-dtv/lib/atsc_rs_decoder_impl.h
@@ -39,7 +39,6 @@ namespace gr {
       int nerrors_corrrected_count;
       int bad_packet_count;
       int total_packets;
-      int reset_counter;
       void *d_rs;
 
     public:
diff --git a/gr-dtv/lib/atsc_single_viterbi.cc 
b/gr-dtv/lib/atsc_single_viterbi.cc
index d8374ca..385940e 100644
--- a/gr-dtv/lib/atsc_single_viterbi.cc
+++ b/gr-dtv/lib/atsc_single_viterbi.cc
@@ -28,39 +28,31 @@ namespace gr {
 
     /* was_sent is a table of what symbol we get given what bit pair
        was sent and what state we where in [state][pair] */
-    const int atsc_single_viterbi::was_sent[8][4] = {
-      {0,2,0,2},
-      {0,2,0,2},
-      {1,3,1,3},
-      {1,3,1,3},
-      {4,6,4,6},
-      {4,6,4,6},
-      {5,7,5,7},
-      {5,7,5,7}
+    const int atsc_single_viterbi::was_sent[4][4] = {
+      {0,2,4,6},
+      {0,2,4,6},
+      {1,3,5,7},
+      {1,3,5,7},
     };
 
     /* transition_table is a table of what state we were in
        given current state and bit pair sent [state][pair] */
-    const int atsc_single_viterbi::transition_table[8][4] = {
-      {0,2,4,6},
-      {2,0,6,4},
-      {1,3,5,7},
-      {3,1,7,5},
-      {4,6,0,2},
-      {6,4,2,0},
-      {5,7,1,3},
-      {7,5,3,1}
+    const int atsc_single_viterbi::transition_table[4][4] = {
+      {0,2,0,2},
+      {2,0,2,0},
+      {1,3,1,3},
+      {3,1,3,1},
     };
 
     void
     atsc_single_viterbi::reset()
     {
       for (unsigned int i = 0; i<2; i++)
-        for (unsigned int j = 0; j<8; j++) {
+        for (unsigned int j = 0; j<4; j++) {
           path_metrics[i][j] = 0;
           traceback[i][j] = 0;
         }
-
+      post_coder_state = 0;
       phase = 0;
     }
 
@@ -81,8 +73,8 @@ namespace gr {
                              (float)fabs( input - 1 ), (float)fabs( input - 3 
),
                              (float)fabs( input - 5 ), (float)fabs( input - 7 
) };
 
-     /* We start by iterating over all possible states */
-      for (unsigned int state = 0; state < 8; state++) {
+      /* We start by iterating over all possible states */
+      for (unsigned int state = 0; state < 4; state++) {
         /* Next we find the most probable path from the previous
            states to the state we are testing, we only need to look at
            the 4 paths that can be taken given the 2-bit input */
@@ -113,12 +105,16 @@ namespace gr {
       }
 
       if(best_state_metric > 10000) {
-        for(unsigned int state = 0; state < 8; state++)
+        for(unsigned int state = 0; state < 4; state++)
           path_metrics[phase^1][state] -= best_state_metric;
       }
       phase ^= 1;
 
-      return (0x3 & traceback[phase][best_state]);
+      int y2 = (0x2 & traceback[phase][best_state]) >> 1;
+      int x2 = y2 ^ post_coder_state;
+      post_coder_state = y2;
+
+      return ( x2 << 1 ) | (0x1 & traceback[phase][best_state]);
     }
 
   } /* namespace dtv */
diff --git a/gr-dtv/lib/atsc_single_viterbi.h b/gr-dtv/lib/atsc_single_viterbi.h
index 4f71369..3c756c7 100644
--- a/gr-dtv/lib/atsc_single_viterbi.h
+++ b/gr-dtv/lib/atsc_single_viterbi.h
@@ -42,15 +42,16 @@ namespace gr {
       void reset ();
 
       //! internal delay of decoder
-      int delay () { return TB_LEN - 1; }
+      static int delay () { return TB_LEN - 1; }
 
     protected:
-      static const int transition_table[8][4];
-      static const int was_sent[8][4];
+      static const int transition_table[4][4];
+      static const int was_sent[4][4];
 
-      float path_metrics [2][8];
-      unsigned long long traceback [2][8];
+      float path_metrics [2][4];
+      unsigned long long traceback [2][4];
       unsigned char phase;
+      int post_coder_state;
     };
 
   } /* namespace dtv */
diff --git a/gr-dtv/lib/atsc_viterbi_decoder_impl.cc 
b/gr-dtv/lib/atsc_viterbi_decoder_impl.cc
index 6c093e2..8e9cbc0 100644
--- a/gr-dtv/lib/atsc_viterbi_decoder_impl.cc
+++ b/gr-dtv/lib/atsc_viterbi_decoder_impl.cc
@@ -28,6 +28,7 @@
 #include "atsc_viterbi_decoder_impl.h"
 #include "atsc_types.h"
 #include <atsc_viterbi_mux.cc> // machine generated
+#include <emmintrin.h>
 
 namespace gr {
   namespace dtv {
@@ -45,7 +46,6 @@ namespace gr {
                    io_signature::make(1, 1, 
sizeof(atsc_mpeg_packet_rs_encoded)))
     {
       set_output_multiple(NCODERS);
-      debug = true;
 
       /*
        * These fifo's handle the alignment problem caused by the
@@ -58,7 +58,7 @@ namespace gr {
        */
 
       // the -4 is for the 4 sync symbols
-      int fifo_size = ATSC_DATA_SEGMENT_LENGTH - 4 - viterbi[0].delay ();
+      int fifo_size = ATSC_DATA_SEGMENT_LENGTH - 4 - viterbi[0].delay();
       for (int i = 0; i < NCODERS; i++)
         fifo[i] = new fifo_t(fifo_size);
 
@@ -74,10 +74,8 @@ namespace gr {
     void
     atsc_viterbi_decoder_impl::reset()
     {
-      for (int i = 0; i < NCODERS; i++)        {
-        viterbi[i].reset();
+      for (int i = 0; i < NCODERS; i++)
         fifo[i]->reset();
-      }
     }
 
     int
@@ -93,32 +91,34 @@ namespace gr {
       // 12, so we should always get a mod 12 numbered first packet
       assert(noutput_items % NCODERS == 0);
 
-      int encoder;
       int dbwhere;
       int dbindex;
       int shift;
-      unsigned char dibit;
-      float symbol;
+      float symbols[NCODERS][enco_which_max];
+      unsigned char dibits[NCODERS][enco_which_max];
 
       unsigned char out_copy[OUTPUT_SIZE];
 
       for (int i = 0; i < noutput_items; i += NCODERS) {
+        /* Build a continuous symbol buffer for each encoder */
+        for (unsigned int encoder = 0; encoder < NCODERS; encoder++)
+          for (unsigned int k = 0; k < enco_which_max; k++)
+            symbols[encoder][k] = in[i + 
(enco_which_syms[encoder][k]/832)].data[enco_which_syms[encoder][k] % 832];
+
         /* Now run each of the 12 Viterbi decoders over their subset of
            the input symbols */
-        for (encoder = 0; encoder < NCODERS; encoder++)        {
-          fifo_t       *dibit_fifo = fifo[encoder];
+        for (unsigned int encoder = 0; encoder < NCODERS; encoder++)
+          for (unsigned int k = 0; k < enco_which_max; k++)
+            dibits[encoder][k] = viterbi[encoder].decode(symbols[encoder][k]);
 
-          /* Feed all the incoming symbols into one decoder;
-             pump them into the relevant dibits. */
+        /* Move dibits into their location in the output buffer */
+        for (unsigned int encoder = 0; encoder < NCODERS; encoder++) {
           for (unsigned int k = 0; k < enco_which_max; k++) {
-            symbol = in[i + 
(enco_which_syms[encoder][k]/832)].data[enco_which_syms[encoder][k] % 832];
-            dibit = dibit_fifo->stuff(viterbi[encoder].decode(symbol));
-
             /* Store the dibit into the output data segment */
             dbwhere = enco_which_dibits[encoder][k];
             dbindex = dbwhere >> 3;
             shift = dbwhere & 0x7;
-            out_copy[dbindex] = (out_copy[dbindex] & ~(0x03 << shift)) | 
(dibit << shift);
+            out_copy[dbindex] = (out_copy[dbindex] & ~(0x03 << shift)) | 
(fifo[encoder]->stuff(dibits[encoder][k]) << shift);
           } /* Symbols fed into one encoder */
         } /* Encoders */
 
diff --git a/gr-dtv/lib/atsc_viterbi_decoder_impl.h 
b/gr-dtv/lib/atsc_viterbi_decoder_impl.h
index 37b988f..b4fbbd1 100644
--- a/gr-dtv/lib/atsc_viterbi_decoder_impl.h
+++ b/gr-dtv/lib/atsc_viterbi_decoder_impl.h
@@ -57,8 +57,7 @@ namespace gr {
       static const int INPUT_SIZE = (ATSC_DATA_SEGMENT_LENGTH * 12);
 
       single_viterbi_t viterbi[NCODERS];
-      fifo_t           *fifo[NCODERS];
-      bool             debug;
+      fifo_t *fifo[NCODERS];
 
     public:
       atsc_viterbi_decoder_impl();
diff --git a/gr-dtv/python/dtv/atsc_rx.py b/gr-dtv/python/dtv/atsc_rx.py
index 9ca93fb..590e5f0 100644
--- a/gr-dtv/python/dtv/atsc_rx.py
+++ b/gr-dtv/python/dtv/atsc_rx.py
@@ -36,7 +36,7 @@ class atsc_rx(gr.hier_block2):
         pll = dtv.atsc_fpll(output_rate)
 
         # Remove pilot tone now at DC
-        dcr = filter.dc_blocker_ff(1024)
+        dcr = filter.dc_blocker_ff(4096)
 
         # Normalize signal to proper constellation amplitude
         agc = analog.agc_ff(1e-5, 4.0)