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Audio Input: quarter sample rate heterodyne for mono signals
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@ -287,6 +287,7 @@ void AudioInput::applySettings(const AudioInputSettings& settings, bool force, b
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if ((m_settings.m_iqMapping != settings.m_iqMapping) || force)
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{
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reverseAPIKeys.append("iqMapping");
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forwardChange = true;
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if (m_worker) {
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m_worker->setIQMapping(settings.m_iqMapping);
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@ -306,7 +307,11 @@ void AudioInput::applySettings(const AudioInputSettings& settings, bool force, b
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if (forwardChange)
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{
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DSPSignalNotification *notif = new DSPSignalNotification(m_settings.m_sampleRate/(1<<m_settings.m_log2Decim), 0);
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qint64 dF =
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((m_settings.m_iqMapping == AudioInputSettings::IQMapping::L) ||
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(m_settings.m_iqMapping == AudioInputSettings::IQMapping::R)) ?
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m_settings.m_sampleRate / 4 : 0;
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DSPSignalNotification *notif = new DSPSignalNotification(m_settings.m_sampleRate/(1<<m_settings.m_log2Decim), dF);
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m_deviceAPI->getDeviceEngineInputMessageQueue()->push(notif);
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}
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}
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@ -37,7 +37,8 @@ AudioInputGui::AudioInputGui(DeviceUISet *deviceUISet, QWidget* parent) :
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m_deviceUISet(deviceUISet),
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m_forceSettings(true),
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m_settings(),
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m_sampleSource(NULL)
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m_sampleSource(nullptr),
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m_centerFrequency(0)
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{
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m_sampleSource = (AudioInput*) m_deviceUISet->m_deviceAPI->getSampleSource();
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@ -130,6 +131,7 @@ void AudioInputGui::handleInputMessages()
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{
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DSPSignalNotification* notif = (DSPSignalNotification*) message;
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m_sampleRate = notif->getSampleRate();
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m_centerFrequency = notif->getCenterFrequency();
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qDebug("AudioInputGui::handleInputMessages: DSPSignalNotification: SampleRate: %d", notif->getSampleRate());
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updateSampleRateAndFrequency();
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@ -160,7 +162,7 @@ void AudioInputGui::updateSampleRateAndFrequency()
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*/
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{
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m_deviceUISet->getSpectrum()->setSampleRate(m_sampleRate);
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m_deviceUISet->getSpectrum()->setCenterFrequency(0);
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m_deviceUISet->getSpectrum()->setCenterFrequency(m_centerFrequency);
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m_deviceUISet->getSpectrum()->setSsbSpectrum(false);
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m_deviceUISet->getSpectrum()->setLsbDisplay(false);
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}
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@ -57,6 +57,7 @@ private:
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QTimer m_updateTimer;
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DeviceSampleSource* m_sampleSource;
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int m_sampleRate;
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qint64 m_centerFrequency;
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MessageQueue m_inputMessageQueue;
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@ -210,6 +210,13 @@
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</property>
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</spacer>
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</item>
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<item>
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<widget class="QLabel" name="decimLabel">
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<property name="text">
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<string>Dec</string>
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</property>
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</widget>
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</item>
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<item>
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<widget class="QComboBox" name="decim">
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<property name="maximumSize">
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@ -243,13 +250,6 @@
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</item>
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</widget>
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</item>
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<item>
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<widget class="QLabel" name="decimLabel">
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<property name="text">
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<string>Dec</string>
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</property>
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</widget>
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</item>
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</layout>
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</item>
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<item>
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@ -336,12 +336,12 @@
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</property>
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<item>
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<property name="text">
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<string>I=L, Q=0</string>
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<string>Mono L</string>
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</property>
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</item>
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<item>
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<property name="text">
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<string>I=R, Q=0</string>
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<string>Mono R</string>
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</property>
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</item>
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<item>
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@ -33,7 +33,8 @@ AudioInputWorker::AudioInputWorker(SampleSinkFifo* sampleFifo, AudioFifo *fifo,
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m_log2Decim(0),
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m_iqMapping(AudioInputSettings::IQMapping::L),
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m_convertBuffer(m_convBufSamples),
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m_sampleFifo(sampleFifo)
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m_sampleFifo(sampleFifo),
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m_quNCOPhase(0)
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{
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}
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@ -56,20 +57,40 @@ void AudioInputWorker::stopWork()
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void AudioInputWorker::workIQ(unsigned int nbRead)
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{
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// Map between left and right audio channels and IQ channels
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if (m_iqMapping == AudioInputSettings::IQMapping::L)
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{
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for (uint32_t i = 0; i < nbRead; i++)
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m_buf[i*2+1] = 0;
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}
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else if (m_iqMapping == AudioInputSettings::IQMapping::R)
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if ((m_iqMapping == AudioInputSettings::IQMapping::L) || // mono
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(m_iqMapping == AudioInputSettings::IQMapping::R))
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{
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for (uint32_t i = 0; i < nbRead; i++)
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{
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m_buf[i*2] = m_buf[i*2+1];
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m_buf[i*2+1] = 0;
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qint16 r = m_buf[i*2 + (m_iqMapping == AudioInputSettings::IQMapping::R ? 1 : 0)]; // real sample
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if (m_quNCOPhase == 0) // 0
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{
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m_buf[i*2] = r; // 1
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m_buf[i*2+1] = 0; // 0
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m_quNCOPhase = 1; // next phase
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}
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else if (m_quNCOPhase == 1) // -pi/2
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{
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m_buf[i*2] = 0; // 0
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m_buf[i*2+1] = -r; // -1
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m_quNCOPhase = 2; // next phase
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}
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else if (m_quNCOPhase == 2) // pi or -pi
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{
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m_buf[i*2] = -r; // -1
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m_buf[i*2+1] = 0; // 0
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m_quNCOPhase = 3; // next phase
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}
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else if (m_quNCOPhase == 3) // pi/2
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{
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m_buf[i*2] = 0; // 0
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m_buf[i*2+1] = r; // 1
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m_quNCOPhase = 0; // next phase
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}
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}
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}
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else if (m_iqMapping == AudioInputSettings::IQMapping::LR)
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else if (m_iqMapping == AudioInputSettings::IQMapping::LR) // stereo - reverse
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{
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for (uint32_t i = 0; i < nbRead; i++)
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{
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@ -79,30 +100,35 @@ void AudioInputWorker::workIQ(unsigned int nbRead)
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}
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}
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decimate(m_buf, nbRead);
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}
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void AudioInputWorker::decimate(qint16 *buf, unsigned int nbRead)
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{
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SampleVector::iterator it = m_convertBuffer.begin();
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switch (m_log2Decim)
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{
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case 0:
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m_decimatorsIQ.decimate1(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate1(&it, buf, 2*nbRead);
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break;
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case 1:
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m_decimatorsIQ.decimate2_cen(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate2_cen(&it, buf, 2*nbRead);
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break;
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case 2:
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m_decimatorsIQ.decimate4_cen(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate4_cen(&it, buf, 2*nbRead);
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break;
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case 3:
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m_decimatorsIQ.decimate8_cen(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate8_cen(&it, buf, 2*nbRead);
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break;
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case 4:
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m_decimatorsIQ.decimate16_cen(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate16_cen(&it, buf, 2*nbRead);
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break;
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case 5:
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m_decimatorsIQ.decimate32_cen(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate32_cen(&it, buf, 2*nbRead);
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break;
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case 6:
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m_decimatorsIQ.decimate64_cen(&it, m_buf, 2*nbRead);
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m_decimatorsIQ.decimate64_cen(&it, buf, 2*nbRead);
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break;
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default:
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break;
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@ -51,8 +51,10 @@ private:
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SampleVector m_convertBuffer;
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SampleSinkFifo* m_sampleFifo;
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Decimators<qint32, qint16, SDR_RX_SAMP_SZ, 16, true> m_decimatorsIQ;
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int m_quNCOPhase; //!< Quarter sample rate pseudo NCO phase index (0, 90, 180, 270)
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void workIQ(unsigned int nbRead);
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void decimate(qint16 *buf, unsigned int nbRead);
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private slots:
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void handleAudio();
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@ -38,9 +38,9 @@ A control to set the input volume. This is not supported by all input audio devi
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<h3>7: Channel Map</h3>
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This controls how the left and right stereo audio channels map on to the IQ channels.
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This controls how the left and right audio channels map on to the IQ channels.
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* I=L, Q=0 - The left audio channel is driven to the I channel. The Q channel is set to 0.
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* I=R, Q=0 - The right audio channel is driven to the I channel. The Q channel is set to 0.
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* I=L, Q=R - The left audio channel is driven to the I channel. The right audio channel is driven to the Q channel.
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* I=R, Q=L - The right audio channel is driven to the I channel. The left audio channel is driven to the Q channel.
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* Mono L - Real samples are taken from the left audio channel and are heterodyned by the fourth of the sample rate (fs/4) to obtain complex samples. Therefore the spectrum of the complex baseband is centered at the fourth of the sample rate (fs/4). As per Nyquist rule only a bandwidth of half of the sample rate (fs/2) is available for real signals. Frequencies outside the [0, fs/2] interval are artefacts and can be eliminated by decimating by a factor of 2.
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* Mono R - Same as above but takes the right audio channel for the real signal.
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* I=L, Q=R - The left audio channel is driven to the I channel. The right audio channel is driven to the Q channel for a complex (analytic signal)input.
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* I=R, Q=L - The right audio channel is driven to the I channel. The left audio channel is driven to the Q channel for a complex (analytic signal)input.
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