js8call/JS8_Mode/Modulator.cpp

#include "Modulator.h"
#include "JS8Submode.h"
#include "JS8_Audio/soundout.h"
#include "JS8_Include/commons.h"
#include "JS8_Main/DriftingDateTime.h"
#include "JS8_UI/mainwindow.h"
#include <QDateTime>
#include <QLoggingCategory>
#include <QtMath>
#include <limits>
#include <numbers>

#include "moc_Modulator.cpp"

Q_DECLARE_LOGGING_CATEGORY(modulator_js8)

namespace {
constexpr double TAU = 2 * std::numbers::pi;
constexpr auto FRAME_RATE = 48000;
constexpr auto MS_PER_SEC = 1000;
} // namespace

void Modulator::start(double const frequency, int const submode,
                      double const txDelay, SoundOutput *const stream,
                      Channel const channel) {
    Q_ASSERT(stream);

    const State current_state = m_state.load();
    if (current_state != State::Idle) {
        qCDebug(modulator_js8)
            << "Modulator does not find itself in state idle, but"
            << (current_state == State::Active          ? "Active"
                : current_state == State::Synchronizing ? "Synchronizing"
                : current_state == State::Idle          ? "Idle"
                                                        : "??What??")
            << "so calling stop()";
        stop();
    }

    m_quickClose = false;
    m_audioFrequency = frequency;
    m_nsps = JS8::Submode::samplesForOneSymbol(submode);
    m_toneSpacing = JS8::Submode::toneSpacing(submode);
    m_isym0 = std::numeric_limits<unsigned>::max();
    m_amp = std::numeric_limits<qint16>::max();
    m_audioFrequency0 = 0.0;
    m_phi = 0.0;
    m_silentFrames = 0;
    m_ic = 0;

    // If we're not tuning, then we'll need to figure out exactly when we
    // should start transmitting; this will depend on the submode in play.

    if (!m_tuning) {
        // Get the nominal transmit start time for this submode, and determine
        // which millisecond of the current transmit period we're currently at.

        qint64 const nowMS = DriftingDateTime::currentMSecsSinceEpoch();
        unsigned const periodMS = JS8::Submode::period(submode) * MS_PER_SEC;
        auto const startDelayMS = JS8::Submode::startDelayMS(submode);
        unsigned const periodOffsetMS = nowMS % periodMS;

        // If we haven't yet hit the nominal start time for the period, then we
        // will need to inject some silence into the transmission; determine the
        // number of silent audio samples required to start audio at the correct
        // amount of delay into the period.
        //
        // If we have hit the nominal start time for the period, adjust for late
        // start if we're not exactly at the nominal start time.

        bool const inTxDelayBeforePeriodStart =
            periodMS <= periodOffsetMS + txDelay * MS_PER_SEC;
        if (inTxDelayBeforePeriodStart) {
            unsigned const additionalMSNeededForTxDelay =
                periodMS - periodOffsetMS;
            qCDebug(modulator_js8) << "Sending" << additionalMSNeededForTxDelay
                                   << "ms silence for TX delay.";
            m_silentFrames = (startDelayMS + additionalMSNeededForTxDelay) *
                             FRAME_RATE / MS_PER_SEC;
        } else if (startDelayMS > periodOffsetMS) {
            qCDebug(modulator_js8)
                << "Starting" << periodOffsetMS
                << "ms late into transmission, skipping some of the"
                << startDelayMS << "ms start delay";
            m_silentFrames =
                (startDelayMS - periodOffsetMS) * FRAME_RATE / MS_PER_SEC;
        } else {
            qCWarning(modulator_js8)
                << "Starting" << periodOffsetMS
                << "ms late into transmission, cutting away initial symbol(s).";
            m_ic = (periodOffsetMS - startDelayMS) * FRAME_RATE / MS_PER_SEC;
        }
    } else {
        qCDebug(modulator_js8) << "Modulator finds it is tuning.";
    }

    initialize(QIODevice::ReadOnly, channel);

    if (0 < m_silentFrames) {
        m_state.store(State::Synchronizing);
        qCDebug(modulator_js8)
            << "Symbol transmission to start after"
            << ((float)m_silentFrames) / FRAME_RATE * MS_PER_SEC
            << "ms of silence.";
    } else {
        m_state.store(State::Active);
        qCDebug(modulator_js8) << "Symbol transmission to start immediately.";
    }

    m_stream = stream;
    if (m_stream) {
        m_stream->restart(this);
    } else {
        qCDebug(modulator_js8)
            << "Modulator::start: no audio output stream assigned";
    }
}

void Modulator::tune(bool const tuning) {
    m_tuning = tuning;
    if (!m_tuning)
        stop(true);
}

void Modulator::stop(bool const quickClose) {
    m_quickClose = quickClose;
    close();
}

void Modulator::close() {
    if (m_stream) {
        if (m_quickClose)
            m_stream->reset();
        else
            m_stream->stop();
    }

    m_state.store(State::Idle);
    AudioDevice::close();
}

qint64 Modulator::readData(char *const data, qint64 const maxSize) {
    if (maxSize == 0)
        return 0;

    Q_ASSERT(!(maxSize % qint64(bytesPerFrame()))); // no torn frames
    Q_ASSERT(isOpen());

    qint64 framesGenerated = 0;
    qint64 const maxFrames = maxSize / bytesPerFrame();
    qint16 *samples = reinterpret_cast<qint16 *>(data);
    qint16 const *const samplesEnd =
        samples + maxFrames * (bytesPerFrame() / sizeof(qint16));

    switch (m_state.load()) {
    case State::Synchronizing: {
        if (m_silentFrames) {
            // Send silence up to end of start delay.

            framesGenerated = qMin(m_silentFrames, maxFrames);

            do {
                samples = load(0, samples);
            } while (--m_silentFrames && samples != samplesEnd);

            if (!m_silentFrames) {
                m_state.store(State::Active);
            }
        }
    }
        [[fallthrough]];

    case State::Active: {
        // Fade out parameters; no fade out during tuning.

        unsigned int const i0 =
            (m_tuning ? 9999 : (JS8_NUM_SYMBOLS - 0.017) * 4.0) * m_nsps;
        unsigned int const i1 =
            (m_tuning ? 9999 : JS8_NUM_SYMBOLS * 4.0) * m_nsps;

        while (samples != samplesEnd && m_ic < i1) {
            unsigned int const isym = m_tuning ? 0 : m_ic / (4.0 * m_nsps);

            if (isym != m_isym0 || m_audioFrequency != m_audioFrequency0) {
                double const toneFrequency =
                    m_audioFrequency + itone[isym] * m_toneSpacing;

                m_dphi = TAU * toneFrequency / FRAME_RATE;
                m_isym0 = isym;
                m_audioFrequency0 = m_audioFrequency;
            }

            m_phi += m_dphi;

            if (m_phi > TAU)
                m_phi -= TAU;
            if (m_ic > i0)
                m_amp = 0.98 * m_amp;
            if (m_ic > i1)
                m_amp = 0.0;

            samples = load(qRound(m_amp * qSin(m_phi)), samples);

            ++framesGenerated;
            ++m_ic;
        }

        if (m_amp == 0.0) {
            m_state.store(State::Idle);
            return framesGenerated * bytesPerFrame();
            m_phi = 0.0;
        }

        m_audioFrequency0 = m_audioFrequency;

        // Done for this chunk; continue on the next call. Pad the
        // block with silence.

        while (samples != samplesEnd) {
            samples = load(0, samples);
            ++framesGenerated;
        }

        return framesGenerated * bytesPerFrame();
    }
        [[fallthrough]];

    case State::Idle:
        break;
    }

    Q_ASSERT(isIdle());
    return 0;
}

Q_LOGGING_CATEGORY(modulator_js8, "modulator.js8", QtWarningMsg)