WSJT-X/Modulator.cpp

#include "Modulator.hpp"
#include <limits>
#include <qmath.h>
#include <QDateTime>
#include <QDebug>
#include "mainwindow.h"

extern float gran();		   // Noise generator (for tests only)
#define RAMP_INCREMENT 64  // MUST be an integral factor of 2^16

#if defined (WSJT_SOFT_KEYING)
# define SOFT_KEYING true
#else
# define SOFT_KEYING false
#endif

double const Modulator::m_twoPi = 2.0 * 3.141592653589793238462;

//    float wpm=20.0;
//    unsigned m_nspd=1.2*48000.0/wpm;
//    m_nspd=3072;                           //18.75 WPM
unsigned const Modulator::m_nspd = 2048 + 512; // 22.5 WPM

Modulator::Modulator (unsigned frameRate, unsigned periodLengthInSeconds, \
                      QObject * parent)
  : AudioDevice (parent)
  , m_phi (0.0)
  , m_framesSent (0)
  , m_frameRate (frameRate)
  , m_period (periodLengthInSeconds)
  , m_state (Idle)
  , m_tuning (false)
  , m_muted (false)
{
  qsrand (QDateTime::currentMSecsSinceEpoch()); // Initialize random seed
}

void Modulator::open (unsigned symbolsLength, double framesPerSymbol, \
         unsigned frequency, Channel channel, bool synchronize, double dBSNR)
{
  // Time according to this computer which becomes our base time
  qint64 ms0 = QDateTime::currentMSecsSinceEpoch() % 86400000;

//  qDebug () << "Modulator: Using soft keying for CW is " << SOFT_KEYING;;

  m_symbolsLength = symbolsLength;
  m_framesSent = 0;
  m_isym0 = std::numeric_limits<unsigned>::max (); // Arbitrary big number
  m_addNoise = dBSNR < 0.;
  m_nsps = framesPerSymbol;
  m_frequency = frequency;
  m_amp = std::numeric_limits<qint16>::max ();

  // noise generator parameters
  if (m_addNoise) {
    m_snr = qPow (10.0, 0.05 * (dBSNR - 6.0));
    m_fac = 3000.0;
    if (m_snr > 1.0) m_fac = 3000.0 / m_snr;
  }

  unsigned mstr = ms0 % (1000 * m_period); // ms in period
  m_ic = (mstr / 1000) * m_frameRate; // we start exactly N seconds
              // into period where N is the next whole second

  m_silentFrames = 0;
  // calculate number of silent frames to send
  if (synchronize && !m_tuning)	{
    m_silentFrames = m_ic + m_frameRate - (mstr * m_frameRate / 1000);
  }

//  qDebug () << "Modulator: starting at " << m_ic / m_frameRate << " sec, sending " << m_silentFrames << " silent frames";

  AudioDevice::open (QIODevice::ReadOnly, channel);
  Q_EMIT stateChanged ((m_state = (synchronize && m_silentFrames) ?
        Synchronizing : Active));
}

qint64 Modulator::readData (char * data, qint64 maxSize)
{
  static int j0=-1;
  static double toneFrequency0;
  double toneFrequency;

  if(maxSize==0) return 0;
  Q_ASSERT (!(maxSize % static_cast<qint64> (bytesPerFrame ()))); // no torn frames
  Q_ASSERT (isOpen ());

  qint64 numFrames (maxSize / bytesPerFrame ());
  qint16 * samples (reinterpret_cast<qint16 *> (data));
  qint16 * end (samples + numFrames * (bytesPerFrame () / sizeof (qint16)));

//  qDebug () << "Modulator: " << numFrames << " requested, m_ic = " << m_ic << ", tune mode is " << m_tuning;
//  qDebug() << "C" << maxSize << numFrames << bytesPerFrame();
  switch (m_state)
  {
  case Synchronizing:
  {
    if (m_silentFrames)	{  // send silence up to first second
      numFrames = qMin (m_silentFrames, numFrames);
      for ( ; samples != end; samples = load (0, samples)) { // silence
	      }
      m_silentFrames -= numFrames;
      return numFrames * bytesPerFrame ();
    }

    Q_EMIT stateChanged ((m_state = Active));
    m_ramp = 0;		// prepare for CW wave shaping
  }
      // fall through

  case Active:
  {
    unsigned isym (m_tuning ? 0 : m_ic / (4.0 * m_nsps)); // Actual fsample=48000
    if (isym >= m_symbolsLength && icw[0] > 0) { // start CW condition
      // Output the CW ID
      m_dphi = m_twoPi * m_frequency / m_frameRate;
      unsigned const ic0 = m_symbolsLength * 4 * m_nsps;
      unsigned j (0);
      qint64 framesGenerated (0);

      while (samples != end) {
        m_phi += m_dphi;
        if (m_phi > m_twoPi) m_phi -= m_twoPi;

        qint16 sample ((SOFT_KEYING ? qAbs (m_ramp - 1) :
                                      (m_ramp ? 32767 : 0)) * qSin (m_phi));

        j = (m_ic - ic0 - 1) / m_nspd + 1;
        bool l0 (icw[j] && icw[j] <= 1); // first element treated specially as it's a count
        j = (m_ic - ic0) / m_nspd + 1;

        if ((m_ramp != 0 && m_ramp != std::numeric_limits<qint16>::min ()) ||
            !!icw[j] != l0) {
          if (!!icw[j] != l0) {
            Q_ASSERT (m_ramp == 0 || m_ramp == std::numeric_limits<qint16>::min ());
          }
          m_ramp += RAMP_INCREMENT; // ramp
        }

        if (j < NUM_CW_SYMBOLS) { // stop condition
          // if (!m_ramp && !icw[j])
          //   {
          // 	sample = 0;
          //   }

          samples = load (postProcessSample (sample), samples);
          ++framesGenerated;
          ++m_ic;
        }
      }

      if (j > static_cast<unsigned> (icw[0])) {
        Q_EMIT stateChanged ((m_state = Idle));
      }

      m_framesSent += framesGenerated;
      return framesGenerated * bytesPerFrame ();
    }

    double const baud (12000.0 / m_nsps);
	// fade out parameters (no fade out for tuning)
    unsigned const i0 = m_tuning ? 999 * m_nsps :
                                   (m_symbolsLength - 0.017) * 4.0 * m_nsps;
    unsigned const i1 = m_tuning ? 999 * m_nsps :
                                   m_symbolsLength * 4.0 * m_nsps;

    for (unsigned i = 0; i < numFrames; ++i) {
      isym = m_tuning ? 0 : m_ic / (4.0 * m_nsps); //Actual fsample=48000
      if (isym != m_isym0) {
        if(m_toneSpacing==0.0) {
          toneFrequency0=m_frequency + itone[isym]*baud;
        } else {
          toneFrequency0=m_frequency + itone[isym]*m_toneSpacing;
        }
        m_dphi = m_twoPi * toneFrequency0 / m_frameRate;
        m_isym0 = isym;
      }

      int j=m_ic/480;
      if(m_fSpread>0.0 and j!=j0) {
        float x1=(float)rand()/RAND_MAX;
        float x2=(float)rand()/RAND_MAX;
        toneFrequency = toneFrequency0 + 0.5*m_fSpread*(x1+x2-1.0);
        m_dphi = m_twoPi * toneFrequency / m_frameRate;
        j0=j;
      }

      m_phi += m_dphi;
      if (m_phi > m_twoPi) m_phi -= m_twoPi;
      if (m_ic > i0) m_amp = 0.98 * m_amp;
      if (m_ic > i1) m_amp = 0.0;

      samples = load (postProcessSample (m_amp * qSin (m_phi)), samples);
	    ++m_ic;
	  }

    if (m_amp == 0.0) { // TODO G4WJS: compare double with zero might not be wise
	    if (icw[0] == 0) {
        // no CW ID to send
        Q_EMIT stateChanged ((m_state = Idle));
        m_framesSent += numFrames;
        return numFrames * bytesPerFrame ();
      }

      m_phi = 0.0;
    }

	// done for this chunk - continue on next call
    m_framesSent += numFrames;
    return numFrames * bytesPerFrame ();
  }
    Q_EMIT stateChanged ((m_state = Idle));
    // fall through

  case Idle:
    break;
  }

  Q_ASSERT (Idle == m_state);
  return 0;
}

qint16 Modulator::postProcessSample (qint16 sample) const
{
  if (m_muted) {  // silent frame
      sample = 0;
  } else if (m_addNoise) {  // Test frame, we'll add noise
    qint32 s = m_fac * (gran () + sample * m_snr / 32768.0);
    if (s > std::numeric_limits<qint16>::max ()) {
      s = std::numeric_limits<qint16>::max ();
    }
    if (s < std::numeric_limits<qint16>::min ()) {
      s = std::numeric_limits<qint16>::min ();
    }
    sample = s;
  }
  return sample;
}