gr-satnogs/lib/cw_to_symbol_impl.cc

/* -*- c++ -*- */
/*
 * gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
 *
 *  Copyright (C) 2016-2018
 *  Libre Space Foundation <http://librespacefoundation.org/>
 *
 *  This program 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 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "cw_to_symbol_impl.h"

#include <limits>
#include <gnuradio/io_signature.h>
#include <satnogs/log.h>
#include <satnogs/utils.h>
#include <boost/version.hpp>
#if BOOST_VERSION >= 106500
#include <boost/integer/common_factor.hpp>
#else
#include <boost/math/common_factor.hpp>
#endif
#include <volk/volk.h>

namespace gr {
namespace satnogs {

cw_to_symbol::sptr
cw_to_symbol::make(double sampling_rate, float threshold, float conf_level,
                   size_t wpm, size_t hysteresis)
{
  return gnuradio::get_initial_sptr(
           new cw_to_symbol_impl(sampling_rate, threshold, conf_level, wpm,
                                 hysteresis));
}

/*
 * The private constructor
 */
cw_to_symbol_impl::cw_to_symbol_impl(double sampling_rate, float threshold,
                                     float conf_level, size_t wpm,
                                     size_t hysteresis) :
  gr::sync_block("cw_to_symbol",
                 gr::io_signature::make(1, 1, sizeof(float)),
                 gr::io_signature::make(0, 0, 0)),
  d_sampling_rate(sampling_rate),
  d_act_thrshld(threshold),
  d_confidence_level(conf_level),
  d_dot_samples((1.2 / wpm) * sampling_rate),
  d_window_size(0),
  d_window_cnt(0),
  d_idle_cnt(0),
  d_dot_windows_num(0),
  d_dec_state(NO_SYNC),
  d_prev_space_symbol(true)
{
  if (wpm < MIN_WPM) {
    throw std::invalid_argument("Decoder can not handle such low WPM setting");
  }

  if (wpm > MAX_WPM) {
    throw std::invalid_argument(
      "Decoder can not handle such high WPM setting");
  }

  if (conf_level > 1.0 || conf_level < 0.5) {
    throw std::invalid_argument(
      "Confidence level should be in the range [0.5, 1.0]");
  }

  if (hysteresis > d_dot_samples / 4) {
    throw std::invalid_argument("Too large hysteresis value");
  }

  message_port_register_in(pmt::mp("act_threshold"));
  message_port_register_out(pmt::mp("out"));

  /* Register the message handlers */
  set_msg_handler(
    pmt::mp("act_threshold"),
    boost::bind(&cw_to_symbol_impl::set_act_threshold_msg_handler, this,
                _1));

  /*
   * Reconsider the dot oulse duration based on the confidence level
   * and hysteresis
   */
  d_dot_samples = d_dot_samples - 2 * (hysteresis * conf_level);


  /*
   * Try to split the CW pulses in smaller windows for detecting faster
   * a false alarm. As we use the window size for setting the history
   * it should have a reasonably size.
   */
  size_t i = 1;
  d_window_size = d_dot_samples / i;
  while (d_window_size > 64) {
    i++;
    d_window_size = d_dot_samples / i;
  }

  /* NOTE: The dot duration should be a perfect multiple of the window */
  while (d_dot_samples % d_window_size != 0) {
    d_window_size++;
  }

  LOG_DEBUG("Dot symbol samples: %lu", d_dot_samples);
  LOG_DEBUG("Window size: %lu", d_window_size);

  /* Set the duration of each symbol in multiples of the window size */
  d_dot_windows_num = d_dot_samples / d_window_size;
  d_dash_windows_num = 3 * d_dot_windows_num;
  d_short_pause_windows_num = d_dash_windows_num;
  d_long_pause_windows_num = 7 * d_dot_windows_num;

  const int alignment_multiple = volk_get_alignment()
                                 / (d_window_size * sizeof(float));
  set_alignment(std::max(1, alignment_multiple));

  d_const_val = (float *) volk_malloc(d_window_size * sizeof(float),
                                      volk_get_alignment());
  d_tmp = (float *) volk_malloc(d_window_size * sizeof(float),
                                volk_get_alignment());
  d_out = (int32_t *) volk_malloc(d_window_size * sizeof(int32_t),
                                  volk_get_alignment());

  if (!d_const_val || !d_tmp || !d_out) {
    throw std::runtime_error("cw_to_symbol: Could not allocate memory");
  }

  for (i = 0; i < d_window_size; i++) {
    d_const_val[i] = threshold;
  }
  set_history(d_window_size);
}

inline void
cw_to_symbol_impl::send_symbol_msg(morse_symbol_t s)
{
  if (s == MORSE_S_SPACE || s == MORSE_L_SPACE) {
    d_prev_space_symbol = true;
  }
  else {
    d_prev_space_symbol = false;
  }
  message_port_pub(pmt::mp("out"), pmt::from_long(s));
}

inline bool
cw_to_symbol_impl::check_conf_level(size_t cnt, size_t target)
{
  return ((float) cnt > target * d_confidence_level);
}

/*
 * Our virtual destructor.
 */
cw_to_symbol_impl::~cw_to_symbol_impl()
{
  volk_free(d_const_val);
  volk_free(d_tmp);
  volk_free(d_out);
}

inline void
cw_to_symbol_impl::set_idle()
{
  d_dec_state = NO_SYNC;
  d_window_cnt = 0;
  d_idle_cnt = 0;
}

inline void
cw_to_symbol_impl::set_short_on()
{
  d_dec_state = SEARCH_DOT;
  d_window_cnt = 1;
}

inline void
cw_to_symbol_impl::set_long_on()
{
  d_dec_state = SEARCH_DASH;
}

inline void
cw_to_symbol_impl::set_search_space()
{
  d_dec_state = SEARCH_SPACE;
  d_window_cnt = 1;
}

void
cw_to_symbol_impl::set_act_threshold_msg_handler(pmt::pmt_t msg)
{
  if (pmt::is_pair(msg)) {
    set_act_threshold(pmt::to_double(pmt::cdr(msg)));
  }
}

int
cw_to_symbol_impl::work(int noutput_items,
                        gr_vector_const_void_star &input_items,
                        gr_vector_void_star &output_items)
{
  bool triggered;
  size_t i;
  const float *in_old = (const float *) input_items[0];
  const float *in = in_old + history() - 1;

  if (noutput_items < 0) {
    return noutput_items;
  }

  /* During idle state search for a possible trigger */
  if (d_dec_state == NO_SYNC) {
    for (i = 0; i < (size_t) noutput_items; i++) {
      /*
       * Clamp the input so the window mean is not affected by strong spikes
       * Good luck understanding this black magic shit!
       */
      triggered = is_triggered(in_old + i, d_window_size);
      if (triggered) {
        LOG_DEBUG("Triggered!");
        set_short_on();
        return i + 1;
      }
    }
    d_idle_cnt += noutput_items / d_window_size;
    if (d_idle_cnt > 10 * d_long_pause_windows_num) {
      send_symbol_msg(MORSE_END_MSG_SPACE);
      d_idle_cnt = 0;
    }
    return noutput_items;
  }

  /* From now one, we handle the input in multiples of a window */
  for (i = 0; i < (size_t) noutput_items / d_window_size; i++) {
    triggered = is_triggered(in + i * d_window_size, d_window_size);
    switch (d_dec_state) {
    case SEARCH_DOT:
      if (triggered) {
        d_window_cnt++;
        if (d_window_cnt > d_dot_windows_num) {
          set_long_on();
          LOG_DEBUG("Going to search for long sequence");
        }
      }
      else {
        if (check_conf_level(d_window_cnt, d_dot_windows_num)) {
          LOG_DEBUG("DOT");
          send_symbol_msg(MORSE_DOT);
        }
        LOG_DEBUG("Going to search for space: win cnt %lu", d_window_cnt);
        set_search_space();
      }
      break;
    case SEARCH_DASH:
      if (triggered) {
        d_window_cnt++;
      }
      else {
        if (check_conf_level(d_window_cnt, d_dash_windows_num)) {
          LOG_DEBUG("DASH");
          send_symbol_msg(MORSE_DASH);
        }
        else {
          LOG_DEBUG("DOT");
          send_symbol_msg(MORSE_DOT);
        }
        set_search_space();
        LOG_DEBUG("Going to search for space");
      }
      break;
    case SEARCH_SPACE:
      if (triggered) {
        if (check_conf_level(d_window_cnt, d_long_pause_windows_num)) {
          LOG_DEBUG("LONG SPACE");
          send_symbol_msg(MORSE_L_SPACE);
        }
        else if (check_conf_level(d_window_cnt, d_short_pause_windows_num)) {
          LOG_DEBUG("SHORT SPACE");
          send_symbol_msg(MORSE_S_SPACE);
        }
        set_short_on();
        LOG_DEBUG("Going to search for dot");
      }
      else {
        d_window_cnt++;
        if (d_window_cnt > d_long_pause_windows_num) {
          LOG_DEBUG("LONG SPACE");
          send_symbol_msg(MORSE_L_SPACE);
          set_idle();
          LOG_DEBUG("Going to idle");
          return (i + 1) * d_window_size;
        }
      }
      break;
    default:
      LOG_ERROR("Invalid decoder state");
    }
  }
  return i * d_window_size;
}

/**
 * Sets a new activation threshold.
 * @param thrhld the new threshold.
 */
void
cw_to_symbol_impl::set_act_threshold(float thrhld)
{
  d_act_thrshld = thrhld;
}

/**
 * Clamps the input and performs at the same time binary slicing.
 * With this way, a decision based on moving average is not affected
 * by strong peaks.
 * @param out the output buffer with the binary sliced output
 * @param in the input signal
 * @param len number of samples to process
 */
inline void
cw_to_symbol_impl::clamp_input(int32_t *out, const float *in, size_t len)
{
  volk_32f_x2_subtract_32f(d_tmp, in, d_const_val, len);
  volk_32f_binary_slicer_32i(d_out, d_tmp, len);
}

static inline int32_t
hadd(const int32_t *in, size_t len)
{
  size_t i;
  int32_t cnt = 0;
  for (i = 0; i < len; i++) {
    cnt += in[i];
  }
  return cnt;
}

inline bool
cw_to_symbol_impl::is_triggered(const float *in, size_t len)
{
  int32_t cnt;
  clamp_input(d_out, in, len);
  cnt = hadd(d_out, len);
  return (cnt >= (int32_t)(d_window_size * d_confidence_level)) ? true : false;
}

} /* namespace satnogs */
} /* namespace gr */