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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_viterbi_decoder.h>
#include <assert.h>
#include <stdio.h>
#include <cmath>
#include "atsci_viterbi_mux.cc"
#include <string.h>
/* How many separate Trellis encoders / Viterbi decoders run in parallel */
static const int NCODERS = 12;
static const float DSEG_SYNC_SYM1 = 5;
static const float DSEG_SYNC_SYM2 = -5;
static const float DSEG_SYNC_SYM3 = -5;
static const float DSEG_SYNC_SYM4 = 5;
atsci_viterbi_decoder::atsci_viterbi_decoder ()
{
debug = true;
/*
* These fifo's handle the alignment problem caused by the
* inherent decoding delay of the individual viterbi decoders.
* The net result is that this entire block has a pipeline latency
* of 12 complete segments.
*
* If anybody cares, it is possible to do it with less delay, but
* this approach is at least somewhat understandable...
*/
// the -4 is for the 4 sync symbols
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);
reset ();
}
atsci_viterbi_decoder::~atsci_viterbi_decoder ()
{
for (int i = 0; i < NCODERS; i++)
delete fifo[i];
}
void
atsci_viterbi_decoder::reset ()
{
for (int i = 0; i < NCODERS; i++){
viterbi[i].reset ();
fifo[i]->reset ();
}
}
void
atsci_viterbi_decoder::decode (atsc_mpeg_packet_rs_encoded out[NCODERS],
const atsc_soft_data_segment in[NCODERS])
{
unsigned char out_copy[OUTPUT_SIZE];
float in_copy[INPUT_SIZE];
// copy input into continguous temporary buffer
for (int i = 0; i < NCODERS; i++){
assert (in[i].pli.regular_seg_p ());
memcpy (&in_copy[i * INPUT_SIZE/NCODERS],
&in[i].data[0],
ATSC_DATA_SEGMENT_LENGTH * sizeof (in_copy[0]));
}
memset (out_copy, 0, sizeof (out_copy)); // sanity check
// do the deed...
decode_helper (out_copy, in_copy);
// copy output from contiguous temp buffer into final output
for (int i = 0; i < NCODERS; i++){
memcpy (&out[i].data[0],
&out_copy[i * OUTPUT_SIZE/NCODERS],
ATSC_MPEG_RS_ENCODED_LENGTH * sizeof (out_copy[0]));
// adjust pipeline info to reflect 12 segment delay
plinfo::delay (out[i].pli, in[i].pli, NCODERS);
}
}
void
atsci_viterbi_decoder::decode_helper (unsigned char out[OUTPUT_SIZE],
const float symbols_in[INPUT_SIZE])
{
int encoder;
unsigned int i;
int dbi;
int dbwhere;
int dbindex;
int shift;
unsigned char dibit;
float symbol;
/* Memset is not necessary if it's all working... */
memset (out, 0, OUTPUT_SIZE);
#define VERBOSE 0
#if 1
/* Check for sync symbols in the incoming data stream */
/* For now, all we do is complain to stdout. FIXME, pass it back to
caller as an error/quality signal. */
for (i = 0; i < sync_symbol_indices_max; i++) {
int j = sync_symbol_indices[i];
if (fabsf (symbols_in[j] - DSEG_SYNC_SYM1) > 1.0)
if (VERBOSE) fprintf (stderr, "** Missing dataseg sync 1 at %d, expect %g, got %g.\n",
j, DSEG_SYNC_SYM1, symbols_in[j]);
j++;
if (fabsf (symbols_in[j] - DSEG_SYNC_SYM2) > 1.0)
if (VERBOSE) fprintf (stderr, "** Missing dataseg sync 2 at %d, expect %g, got %g.\n",
j, DSEG_SYNC_SYM2, symbols_in[j]);
j++;
if (fabsf (symbols_in[j] - DSEG_SYNC_SYM3) > 1.0)
if (VERBOSE) fprintf (stderr, "** Missing dataseg sync 3 at %d, expect %g, got %g.\n",
j, DSEG_SYNC_SYM3, symbols_in[j]);
j++;
if (fabsf (symbols_in[j] - DSEG_SYNC_SYM4) > 1.0)
if (VERBOSE) fprintf (stderr, "** Missing dataseg sync 4 at %d, expect %g, got %g.\n",
j, DSEG_SYNC_SYM4, symbols_in[j]);
}
#endif
#undef VERBOSE
// printf ("@@@ DIBITS @@@\n");
/* Now run each of the 12 Trellis encoders over their subset of
the input symbols */
for (encoder = 0; encoder < NCODERS; encoder++) {
dbi = 0; /* Reinitialize dibit index for new encoder */
fifo_t *dibit_fifo = fifo[encoder];
/* Feed all the incoming symbols into one encoder;
pump them into the relevant dibits. */
for (i = 0; i < enco_which_max; i++) {
symbol = symbols_in[enco_which_syms[encoder][i]];
dibit = dibit_fifo->stuff (viterbi[encoder].decode (symbol));
// printf ("%d\n", dibit);
/* Store the dibit into the output data segment */
dbwhere = enco_which_dibits[encoder][dbi++];
dbindex = dbwhere >> 3;
shift = dbwhere & 0x7;
out[dbindex] =
(out[dbindex] & ~(0x03 << shift)) | (dibit << shift);
} /* Symbols fed into one encoder */
} /* Encoders */
// fflush (stdout);
}
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