Method startTxStream

src/core/AudioEngine.cpp:5738–6092

// ─── TX stream ────────────────────────────────────────────────────────────────

bool AudioEngine::startTxStream(const QHostAddress& radioAddress, quint16 radioPort)
{
    if (m_audioSource) return true;  // already running

    // WASAPI silent-open recovery (#2929). If the previous open was driven
    // by the silence watchdog, m_txForceMonoOnNextOpen is true; consume it
    // here. A fresh (non-watchdog) start re-enables the one-shot retry budget.
    const bool isWatchdogRetry = m_txForceMonoOnNextOpen;
    m_txForceMonoOnNextOpen = false;
    if (!isWatchdogRetry) {
        m_txSilenceRetryDone = false;
    }
    m_txReceivedAnyBytes = false;

    m_txAddress = radioAddress;
    m_txPort    = radioPort;
    m_txPacketCount = 0;
    m_txAccumulator.clear();
    m_txMicChannelState.reset();
    m_lastTxMicChannelLog.invalidate();

    // TX mic capture uses Int16 — we convert to float32 after capture.
    // (makeFormat() returns Float for the RX sink, but mic hardware is Int16.)
    QAudioFormat fmt;
    fmt.setSampleRate(DEFAULT_SAMPLE_RATE);
    fmt.setChannelCount(2);
    fmt.setSampleFormat(QAudioFormat::Int16);
    QAudioDevice dev = QMediaDevices::defaultAudioInput();
    bool txFallbackOccurred = false;
    QStringList txFallbackReasons;
    QStringList txFormatAttempts;
    const auto noteTxFallback = [&txFallbackOccurred, &txFallbackReasons](const QString& reason) {
        txFallbackOccurred = true;
        if (!reason.isEmpty() && !txFallbackReasons.contains(reason)) {
            txFallbackReasons << reason;
        }
    };
    const auto noteTxAttempt = [&txFormatAttempts](const QAudioFormat& format) {
        const QString attempt = formatAudioAttempt(format.sampleRate(),
                                                  format.channelCount(),
                                                  format.sampleFormat());
        if (!txFormatAttempts.contains(attempt)) {
            txFormatAttempts << attempt;
        }
    };
    if (!m_inputDevice.isNull()) {
        const auto inputs = QMediaDevices::audioInputs();
        if (devicePresent(inputs, m_inputDevice)) {
            dev = m_inputDevice;
        } else {
            qCWarning(lcAudio) << "AudioEngine: saved input device is unavailable, using the system default input instead";
            noteTxFallback(QStringLiteral("saved input unavailable -> system default"));
            m_inputDevice = QAudioDevice{};
        }
    }

    if (dev.isNull()) {
        qCWarning(lcAudio) << "AudioEngine: no audio input device available";