NFM demod: added high pass audio filter control

plugins/channelrx/demodnfm/nfmdemod.cpp

@@ -90,7 +90,7 @@ NFMDemod::NFMDemod(DeviceAPI *devieAPI) :
 	m_ctcssDetector.setCoefficients(m_audioSampleRate/16, m_audioSampleRate/8.0f); // 0.5s / 2 Hz resolution
 	m_afSquelch.setCoefficients(m_audioSampleRate/2000, 600, m_audioSampleRate, 200, 0, afSqTones); // 0.5ms test period, 300ms average span, audio SR, 100ms attack, no decay
 
-    m_lowpass.create(301, m_audioSampleRate, 250.0);
+    m_ctcssLowpass.create(301, m_audioSampleRate, 250.0);
 
     applyChannelSettings(m_inputSampleRate, m_inputFrequencyOffset, true);
 	applySettings(m_settings, true);
@@ -247,7 +247,7 @@ void NFMDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
                 {
                     if (m_settings.m_ctcssOn)
                     {
-                        Real ctcss_sample = m_lowpass.filter(demod * m_discriCompensation);
+                        Real ctcss_sample = m_ctcssLowpass.filter(demod * m_discriCompensation);
 
                         if ((m_sampleCount & 7) == 7) // decimate 48k -> 6k
                         {
@@ -287,7 +287,11 @@ void NFMDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
                     }
                     else
                     {
-                        sample = m_bandpass.filter(m_squelchDelayLine.readBack(m_squelchGate)) * m_settings.m_volume;
+                        if (m_settings.m_highPass) {
+                            sample = m_bandpass.filter(m_squelchDelayLine.readBack(m_squelchGate)) * m_settings.m_volume;
+                        } else {
+                            sample = m_lowpass.filter(m_squelchDelayLine.readBack(m_squelchGate)) * m_settings.m_volume;
+                        }
                     }
                 }
                 else
@@ -436,8 +440,9 @@ void NFMDemod::applyAudioSampleRate(int sampleRate)
     m_interpolator.create(16, m_inputSampleRate, m_settings.m_rfBandwidth / 2.2f);
     m_interpolatorDistanceRemain = 0;
     m_interpolatorDistance = (Real) m_inputSampleRate / (Real) sampleRate;
-    m_lowpass.create(301, sampleRate, 250.0);
+    m_ctcssLowpass.create(301, sampleRate, 250.0);
     m_bandpass.create(301, sampleRate, 300.0, m_settings.m_afBandwidth);
+    m_lowpass.create(301, sampleRate, m_settings.m_afBandwidth);
     m_squelchGate = (sampleRate / 100) * m_settings.m_squelchGate; // gate is given in 10s of ms at 48000 Hz audio sample rate
     m_squelchCount = 0; // reset squelch open counter
     m_ctcssDetector.setCoefficients(sampleRate/16, sampleRate/8.0f); // 0.5s / 2 Hz resolution
@@ -499,6 +504,7 @@ void NFMDemod::applySettings(const NFMDemodSettings& settings, bool force)
             << " m_squelch: " << settings.m_squelch
             << " m_ctcssIndex: " << settings.m_ctcssIndex
             << " m_ctcssOn: " << settings.m_ctcssOn
+            << " m_highPass: " << m_settings.m_highPass
             << " m_audioMute: " << settings.m_audioMute
             << " m_audioDeviceName: " << settings.m_audioDeviceName
             << " m_useReverseAPI: " << settings.m_useReverseAPI
@@ -550,6 +556,7 @@ void NFMDemod::applySettings(const NFMDemodSettings& settings, bool force)
         reverseAPIKeys.append("afBandwidth");
         m_settingsMutex.lock();
         m_bandpass.create(301, m_audioSampleRate, 300.0, settings.m_afBandwidth);
+        m_lowpass.create(301, m_audioSampleRate, settings.m_afBandwidth);
         m_settingsMutex.unlock();
     }
 
@@ -591,6 +598,10 @@ void NFMDemod::applySettings(const NFMDemodSettings& settings, bool force)
         setSelectedCtcssIndex(settings.m_ctcssIndex);
     }
 
+    if ((settings.m_highPass != m_settings.m_highPass) || force) {
+        reverseAPIKeys.append("highPass");
+    }
+
     if ((settings.m_audioDeviceName != m_settings.m_audioDeviceName) || force)
     {
         reverseAPIKeys.append("audioDeviceName");

plugins/channelrx/demodnfm/nfmdemod.h

@@ -220,8 +220,9 @@ private:
 	Interpolator m_interpolator;
 	Real m_interpolatorDistance;
 	Real m_interpolatorDistanceRemain;
-	Lowpass<Real> m_lowpass;
+	Lowpass<Real> m_ctcssLowpass;
 	Bandpass<Real> m_bandpass;
+    Lowpass<Real> m_lowpass;
 	CTCSSDetector m_ctcssDetector;
 	int m_ctcssIndex; // 0 for nothing detected
 	int m_ctcssIndexSelected;

plugins/channelrx/demodnfm/nfmdemodgui.cpp

@@ -201,6 +201,12 @@ void NFMDemodGUI::on_ctcssOn_toggled(bool checked)
 	applySettings();
 }
 
+void NFMDemodGUI::on_highPassFilter_toggled(bool checked)
+{
+    m_settings.m_highPass = checked;
+    applySettings();
+}
+
 void NFMDemodGUI::on_audioMute_toggled(bool checked)
 {
 	m_settings.m_audioMute = checked;
@@ -398,6 +404,7 @@ void NFMDemodGUI::displaySettings()
     }
 
     ui->ctcssOn->setChecked(m_settings.m_ctcssOn);
+    ui->highPassFilter->setChecked(m_settings.m_highPass);
     ui->audioMute->setChecked(m_settings.m_audioMute);
 
     ui->ctcss->setCurrentIndex(m_settings.m_ctcssIndex);

plugins/channelrx/demodnfm/nfmdemodgui.h

@@ -76,6 +76,7 @@ private slots:
 	void on_squelch_valueChanged(int value);
 	void on_ctcss_currentIndexChanged(int index);
 	void on_ctcssOn_toggled(bool checked);
+    void on_highPassFilter_toggled(bool checked);
 	void on_audioMute_toggled(bool checked);
 	void onWidgetRolled(QWidget* widget, bool rollDown);
 	void onMenuDialogCalled(const QPoint& p);

plugins/channelrx/demodnfm/nfmdemodgui.ui

@@ -574,6 +574,20 @@
         </property>
        </spacer>
       </item>
+      <item>
+       <widget class="ButtonSwitch" name="highPassFilter">
+        <property name="toolTip">
+         <string>High pass audio filter</string>
+        </property>
+        <property name="text">
+         <string/>
+        </property>
+        <property name="icon">
+         <iconset resource="../../../sdrgui/resources/res.qrc">
+          <normaloff>:/filter_highpass.png</normaloff>:/filter_highpass.png</iconset>
+        </property>
+       </widget>
+      </item>
       <item>
        <widget class="QToolButton" name="audioMute">
         <property name="toolTip">

plugins/channelrx/demodnfm/nfmdemodsettings.cpp

@@ -53,6 +53,7 @@ void NFMDemodSettings::resetToDefaults()
     m_rgbColor = QColor(255, 0, 0).rgb();
     m_title = "NFM Demodulator";
     m_audioDeviceName = AudioDeviceManager::m_defaultDeviceName;
+    m_highPass = true;
     m_useReverseAPI = false;
     m_reverseAPIAddress = "127.0.0.1";
     m_reverseAPIPort = 8888;
@@ -68,6 +69,7 @@ QByteArray NFMDemodSettings::serialize() const
     s.writeS32(3, m_afBandwidth/1000.0);
     s.writeS32(4, m_volume*10.0);
     s.writeS32(5, static_cast<int>(m_squelch));
+    s.writeBool(6, m_highPass);
     s.writeU32(7, m_rgbColor);
     s.writeS32(8, m_ctcssIndex);
     s.writeBool(9, m_ctcssOn);
@@ -123,6 +125,7 @@ bool NFMDemodSettings::deserialize(const QByteArray& data)
         m_volume = tmp / 10.0;
         d.readS32(5, &tmp, -30);
         m_squelch = (tmp < -100 ? tmp/10 : tmp) * 1.0;
+        d.readBool(6, &m_highPass, true);
         d.readU32(7, &m_rgbColor, QColor(255, 0, 0).rgb());
         d.readS32(8, &m_ctcssIndex, 0);
         d.readBool(9, &m_ctcssOn, false);

plugins/channelrx/demodnfm/nfmdemodsettings.h

@@ -42,6 +42,7 @@ struct NFMDemodSettings
     quint32 m_rgbColor;
     QString m_title;
     QString m_audioDeviceName;
+    bool m_highPass;
     bool m_useReverseAPI;
     QString m_reverseAPIAddress;
     uint16_t m_reverseAPIPort;