X-Git-Url: https://git.gag.com/?p=debian%2Fgnuradio;a=blobdiff_plain;f=gr-atsc%2Fsrc%2Flib%2Fatsci_fs_checker_naive.cc;fp=gr-atsc%2Fsrc%2Flib%2Fatsci_fs_checker_naive.cc;h=ab50aff8bd5bdfb85ba65f733f250b5032d38c18;hp=0000000000000000000000000000000000000000;hb=35e43e8d8c271e6842191cac3fc3f2f88a861183;hpb=ea29b08aeb54227e6628f655ccfdb96fe4d8c378

diff --git a/gr-atsc/src/lib/atsci_fs_checker_naive.cc b/gr-atsc/src/lib/atsci_fs_checker_naive.cc
new file mode 100644
index 00000000..ab50aff8
--- /dev/null
+++ b/gr-atsc/src/lib/atsci_fs_checker_naive.cc
@@ -0,0 +1,140 @@
+/* -*- 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_checker_naive.h>
+#include <atsci_syminfo.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_checker_naive::s_511[LENGTH_511];
+unsigned char atsci_fs_checker_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_checker_naive::atsci_fs_checker_naive ()
+{
+  init_s_511 (s_511);
+  init_s_63 (s_63);
+  reset ();
+}
+
+atsci_fs_checker_naive::~atsci_fs_checker_naive ()
+{
+}
+
+void
+atsci_fs_checker_naive::reset ()
+{
+  d_index = 0;
+  memset (d_sample_sr, 0, sizeof (d_sample_sr));
+  memset (d_tag_sr, 0, sizeof (d_tag_sr));
+  memset (d_bit_sr, 0, sizeof (d_bit_sr));
+  d_field_num = 0;
+  d_segment_num = 0;
+}
+
+void
+atsci_fs_checker_naive::filter (float input_sample, atsc::syminfo input_tag,
+			       float *output_sample, atsc::syminfo *output_tag)
+{
+  atsc::syminfo	proto_tag = d_tag_sr[d_index];	// oldest tag in the queue
+
+  if (proto_tag.symbol_num == 0){		// check for field sync pattern
+    
+    d_segment_num = (d_segment_num + 1) & atsc::SI_SEGMENT_NUM_MASK;  // increment
+
+    // 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){	// 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){
+	d_segment_num = atsc::SI_FIELD_SYNC_SEGMENT_NUM;	// this is FIELD_SYNC_1
+	d_field_num = 0;
+      }
+      else if (errors >= (LENGTH_2ND_63 - PN63_ERROR_LIMIT)){
+	d_segment_num = atsc::SI_FIELD_SYNC_SEGMENT_NUM;	// this is FIELD_SYNC_2
+	d_field_num = 1;
+      }
+      else {
+	// should be extremely rare.
+	cerr << "!!! atsci_fs_checker_naive: PN63 error count = " << errors << endl;
+      }
+    }
+  }
+
+  proto_tag.segment_num = d_segment_num;	// fill in segment number and field number	
+  proto_tag.field_num = d_field_num;
+
+  // return oldest sample
+  *output_sample = d_sample_sr[d_index];
+  *output_tag    = proto_tag;
+
+  // overwrite with newest sample;
+  d_sample_sr[d_index] = input_sample;
+  d_bit_sr[d_index] = input_sample < 0 ? 0 : 1;
+  d_tag_sr[d_index] = input_tag;
+  d_index = incr (d_index);
+}
+
+int
+atsci_fs_checker_naive::delay () const
+{
+  return SRSIZE;
+}