Merge branch 'dfsg-orig'

[debian/gnuradio] / gr-atsc / src / lib / atsci_fs_correlator_naive.cc

diff --git a/gr-atsc/src/lib/atsci_fs_correlator_naive.cc b/gr-atsc/src/lib/atsci_fs_correlator_naive.cc
new file mode 100644 (file)
index 0000000..695641c
--- /dev/null
+++ b/gr-atsc/src/lib/atsci_fs_correlator_naive.cc
@@ -0,0 +1,125 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2002 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <atsci_fs_correlator_naive.h>
+#include <atsci_sync_tag.h>
+#include <atsci_pnXXX.h>
+#include <iostream>
+#include <cstring>
+
+using std::cerr;
+using std::endl;
+
+static const int PN511_ERROR_LIMIT = 20;       // max number of bits wrong
+static const int PN63_ERROR_LIMIT =   5;
+
+unsigned char atsci_fs_correlator_naive::s_511[LENGTH_511];
+unsigned char atsci_fs_correlator_naive::s_63[LENGTH_2ND_63];
+
+static void
+init_s_511 (unsigned char *p)
+{
+  *p++ = 1;    // data segment sync pattern
+  *p++ = 0;
+  *p++ = 0;
+  *p++ = 1;
+
+  for (int i = 0; i < 511; i++){
+    p[i] = atsc_pn511[i];
+  }
+}
+
+static void
+init_s_63 (unsigned char *p)
+{
+  for (int i = 0; i < 63; i++){
+    p[i] = atsc_pn63[i];
+  }
+}
+
+atsci_fs_correlator_naive::atsci_fs_correlator_naive ()
+{
+  init_s_511 (s_511);
+  init_s_63 (s_63);
+  reset ();
+}
+
+atsci_fs_correlator_naive::~atsci_fs_correlator_naive ()
+{
+}
+
+void
+atsci_fs_correlator_naive::reset ()
+{
+  d_index = 0;
+  memset (d_sample_sr, 0, sizeof (d_sample_sr));
+  memset (d_bit_sr, 0, sizeof (d_bit_sr));
+}
+
+void
+atsci_fs_correlator_naive::filter (float input_sample,
+                                 float *output_sample, float *output_tag)
+{
+  // check for a hit on the PN 511 pattern
+  int  errors = 0;
+  int  start = wrap (d_index + OFFSET_511);
+
+  for (int i = 0; i < LENGTH_511 && errors < PN511_ERROR_LIMIT; i++)
+    errors += d_bit_sr[wrap (start + i)] ^ s_511[i];
+
+  if (errors >= PN511_ERROR_LIMIT)
+    *output_tag = atsc_sync_tag::NORMAL;
+
+  else {       // 511 pattern is good.  determine if this is field 1 or field 2
+    errors = 0;
+    start = wrap (d_index + OFFSET_2ND_63);
+    for (int i = 0; i < LENGTH_2ND_63; i++)
+      errors += d_bit_sr[wrap (start + i)] ^ s_63[i];
+
+    // we should have either field 1 (== PN63) or field 2 (== ~PN63)
+    if (errors <= PN63_ERROR_LIMIT)
+      *output_tag = atsc_sync_tag::START_FIELD_SYNC_1;
+
+    else if (errors >= (LENGTH_2ND_63 - PN63_ERROR_LIMIT))
+      *output_tag = atsc_sync_tag::START_FIELD_SYNC_2;
+
+    else {
+      // should be extremely rare.
+      cerr << "!!! atsci_fs_correlator_naive: PN63 error count = " << errors << endl;
+      *output_tag = atsc_sync_tag::NORMAL;
+    }
+  }
+
+  // return oldest sample
+  *output_sample = d_sample_sr[d_index];
+
+  // overwrite with newest sample;
+  d_sample_sr[d_index] = input_sample;
+  d_bit_sr[d_index] = input_sample < 0 ? 0 : 1;
+  d_index = incr (d_index);
+}
+
+int
+atsci_fs_correlator_naive::delay () const
+{
+  return SRSIZE;
+}