/usr/include/gnuradio/atsc/sssr_impl.h is in gnuradio-dev 3.7.9.1-2ubuntu1.
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/*
* 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.
*/
/*
* --- ATSC Segment and Symbol Sync Recovery ---
*/
#ifndef _ATSC_SSSR_H_
#define _ATSC_SSSR_H_
#include <gnuradio/atsc/api.h>
#include <gnuradio/atsc/consts.h>
#include <gnuradio/filter/mmse_fir_interpolator_ff.h>
#include <gnuradio/filter/single_pole_iir.h>
#include <cstdio>
/*
* --- support classes for atsci_sssr ---
*/
namespace sssr {
typedef float sample_t;
// ----------------------------------------------------------------
//! digital correlator for 1001 and 0110 patterns
class ATSC_API digital_correlator {
int d_sr; // 4 bit shift register
public:
// Constructor
digital_correlator () { reset (); }
// Manipulators
//! called on channel change
void reset () { d_sr = 0; }
//! clock bit in and return true if we've seen 1001
bool update (int bit) {
d_sr = ((bit & 1) << 3) | (d_sr >> 1);
return (d_sr == 0x9); // 1001
}
};
// ----------------------------------------------------------------
//! segment sync integrator
class ATSC_API seg_sync_integrator {
signed char d_integrator[ATSC_DATA_SEGMENT_LENGTH];
public:
// Constructor
seg_sync_integrator () { reset (); }
// Manipulators
//! called on channel change
void reset ();
//! update current tap with weight and return integrated correlation value
int update (int weight, int index);
//! return index of maximum correlation value
int find_max (int *value);
};
// ----------------------------------------------------------------
//! quad filter (used to compute timing error)
class ATSC_API quad_filter {
sample_t d_delay[4];
public:
// Constructor
quad_filter () { reset (); }
// Manipulators
//! called on channel change
void reset () { d_delay[0] = d_delay[1] = d_delay[2] = d_delay[3] = 0; }
double update (sample_t sample){
d_delay[3] = d_delay[2];
d_delay[2] = d_delay[1];
d_delay[1] = d_delay[0];
d_delay[0] = sample;
// the coefficients are -1,-1,+1,+1
return d_delay[3] + d_delay[2] - d_delay[1] - d_delay[0];
}
};
}
// ----------------------------------------------------------------
/*!
* \brief ATSC Segment and Symbol Sync Recovery
*
* This class implements data segment sync tracking and symbol timing
* using the method described in "ATSC/VSB Tutorial - Receiver Technology"
* by Wayne E. Bretl of Zenith, pgs 41-45.
*/
class ATSC_API atsci_sssr {
sssr::digital_correlator d_correlator;
sssr::seg_sync_integrator d_integrator;
sssr::quad_filter d_quad_filter;
double d_quad_output[ATSC_DATA_SEGMENT_LENGTH];
double d_timing_adjust;
int d_counter; // free running mod 832 counter
int d_symbol_index;
bool d_seg_locked;
FILE *d_debug_fp;
bool incr_counter () {
d_counter++;
if (d_counter >= ATSC_DATA_SEGMENT_LENGTH){
d_counter = 0;
return true;
}
return false;
}
void incr_symbol_index () {
d_symbol_index++;
if (d_symbol_index >= ATSC_DATA_SEGMENT_LENGTH)
d_symbol_index = 0;
}
public:
// Constructor
atsci_sssr ();
~atsci_sssr ();
// Manipulators
//! call on channel change
void reset ();
/*!
* \brief process a single sample at the ATSC symbol rate (~10.76 MSPS)
*
* This block computes an indication of our timing error and keeps
* track of where the segment sync's occur. \p timing_adjust is
* returned to indicate how the interpolator timing needs to be
* adjusted to track the transmitter's symbol timing. If \p seg_locked
* is true, then \p symbol_index is the index of this sample in
* the current segment. The symbols are numbered from 0 to 831, where
* symbols 0, 1, 2 and 3 correspond to the data segment sync pattern,
* nominally +5, -5, -5, +5.
*/
void update (sssr::sample_t sample_in, // input
bool *seg_locked, // are we seeing segment syncs?
int *symbol_index, // 0..831
double *timing_adjust); // how much to adjust timing
};
// ----------------------------------------------------------------
/*!
* \brief interpolator control for segment and symbol sync recovery
*/
class ATSC_API atsci_interpolator {
gr::filter::mmse_fir_interpolator_ff d_interp;
gr::filter::single_pole_iir<float,float,float> d_loop; // ``VCO'' loop filter
double d_nominal_ratio_of_rx_clock_to_symbol_freq; // FREQ
double d_w; // ratio of PERIOD of Tx to Rx clocks
double d_mu; // fractional delay [0,1]
int d_incr; // diagnostic only
FILE *d_debug_fp; // diagnostic only
public:
//! \p nominal_ratio_of_rx_clock_to_symbol_freq must be >= 1.8
atsci_interpolator (double nominal_ratio_of_rx_clock_to_symbol_freq);
~atsci_interpolator ();
// Manipulators
//! call on channel change
void reset ();
/*!
* \brief produce next sample referenced to Tx clock
*
* If there aren't enough input_samples left to produce
* an output, return false, else true.
*/
bool update (const sssr::sample_t input_samples[], // I: vector of samples
int nsamples, // I: total number of samples
int *index, // I/O: current input index
double timing_adjustment, // I: how much to bump timing
sssr::sample_t *output_sample); // O: the output sample
// Accessors
// how much history we require on our input
unsigned ntaps () const { return d_interp.ntaps (); }
// diagnostic accessors
double mu () const { return d_mu; }
double w () const { return d_w; }
int incr () const { return d_incr; }
};
#endif /* _ATSC_SSSR_H_ */
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