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/* -*- 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;
}
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