#1568 Updates NBFM decoder configuration so user can enable/disable high-pass filter option in the audio module to effect audio playback and audio recording of the demodulated audio. Disabling the filter allows recording of DC and sub-audible signalling that may be present in the demodulated audio (e.g. LTR or squelching signalling). (#1569)

Co-authored-by: sheirerd <sheirerd@ainfosec.com>

src/main/java/io/github/dsheirer/audio/AudioModule.java

@@ -43,6 +43,7 @@ public class AudioModule extends AbstractAudioModule implements ISquelchStateLis
 {
     private static final Logger mLog = LoggerFactory.getLogger(AudioModule.class);
     private static float[] sHighPassFilterCoefficients;
+    private final boolean mAudioFilterEnable;
 
     static
     {
@@ -70,27 +71,33 @@ public class AudioModule extends AbstractAudioModule implements ISquelchStateLis
         }
     }
 
-    private IRealFilter mHighPassFilter = FilterFactory.getRealFilter(sHighPassFilterCoefficients);
+    private final IRealFilter mHighPassFilter = FilterFactory.getRealFilter(sHighPassFilterCoefficients);
-    private SquelchStateListener mSquelchStateListener = new SquelchStateListener();
+    private final SquelchStateListener mSquelchStateListener = new SquelchStateListener();
     private SquelchState mSquelchState = SquelchState.SQUELCH;
 
     /**
      * Creates an Audio Module.
      *
      * @param aliasList for aliasing identifiers
+     * @param timeslot for this audio module
      * @param maxAudioSegmentLength in milliseconds
+     * @param audioFilterEnable to enable or disable high-pass audio filter
      */
-    public AudioModule(AliasList aliasList, int timeslot, long maxAudioSegmentLength)
+    public AudioModule(AliasList aliasList, int timeslot, long maxAudioSegmentLength, boolean audioFilterEnable)
     {
         super(aliasList, timeslot, maxAudioSegmentLength);
+        mAudioFilterEnable = audioFilterEnable;
     }
 
     /**
      * Creates an Audio Module.
+     * @param aliasList for aliasing identifiers
+     * @param audioFilterEnable to enable or disable high-pass audio filter
      */
-    public AudioModule(AliasList aliasList)
+    public AudioModule(AliasList aliasList, boolean audioFilterEnable)
     {
         super(aliasList);
+        mAudioFilterEnable = audioFilterEnable;
     }
 
     @Override
@@ -121,7 +128,11 @@ public class AudioModule extends AbstractAudioModule implements ISquelchStateLis
     {
         if(mSquelchState == SquelchState.UNSQUELCH)
         {
-            audioBuffer = mHighPassFilter.filter(audioBuffer);
+            if(mAudioFilterEnable)
+            {
+                audioBuffer = mHighPassFilter.filter(audioBuffer);
+            }
+
             addAudio(audioBuffer);
         }
     }

src/main/java/io/github/dsheirer/gui/playlist/channel/NBFMConfigurationEditor.java

@@ -27,6 +27,7 @@ import io.github.dsheirer.gui.playlist.eventlog.EventLogConfigurationEditor;
 import io.github.dsheirer.gui.playlist.source.FrequencyEditor;
 import io.github.dsheirer.gui.playlist.source.SourceConfigurationEditor;
 import io.github.dsheirer.module.decode.DecoderType;
+import io.github.dsheirer.module.decode.analog.DecodeConfigAnalog;
 import io.github.dsheirer.module.decode.config.AuxDecodeConfiguration;
 import io.github.dsheirer.module.decode.config.DecodeConfiguration;
 import io.github.dsheirer.module.decode.nbfm.DecodeConfigNBFM;
@@ -40,8 +41,6 @@ import io.github.dsheirer.record.RecorderType;
 import io.github.dsheirer.record.config.RecordConfiguration;
 import io.github.dsheirer.source.config.SourceConfiguration;
 import io.github.dsheirer.source.tuner.manager.TunerManager;
-import java.util.ArrayList;
-import java.util.List;
 import javafx.beans.value.ChangeListener;
 import javafx.beans.value.ObservableValue;
 import javafx.collections.ListChangeListener;
@@ -58,15 +57,15 @@ import javafx.scene.layout.GridPane;
 import javafx.scene.text.TextAlignment;
 import org.controlsfx.control.SegmentedButton;
 import org.controlsfx.control.ToggleSwitch;
-import org.slf4j.Logger;
+
-import org.slf4j.LoggerFactory;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * Narrow-Band FM channel configuration editor
  */
 public class NBFMConfigurationEditor extends ChannelConfigurationEditor
 {
-    private final static Logger mLog = LoggerFactory.getLogger(NBFMConfigurationEditor.class);
     private TitledPane mAuxDecoderPane;
     private TitledPane mDecoderPane;
     private TitledPane mEventLogPane;
@@ -75,8 +74,9 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
     private TextField mTalkgroupField;
     private TextField mSquelchThresholdField;
     private ToggleSwitch mSquelchAutoTrackSwitch;
+    private ToggleSwitch mAudioFilterEnable;
     private TextFormatter<Integer> mTalkgroupTextFormatter;
-    private IntegerFormatter mSquelchTextFormatter = new IntegerFormatter((int)DbPowerMeter.DEFAULT_MINIMUM_POWER,
+    private final IntegerFormatter mSquelchTextFormatter = new IntegerFormatter((int)DbPowerMeter.DEFAULT_MINIMUM_POWER,
             (int)DbPowerMeter.DEFAULT_MAXIMUM_POWER);
     private ToggleSwitch mBasebandRecordSwitch;
     private SegmentedButton mBandwidthButton;
@@ -84,9 +84,9 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
     private SourceConfigurationEditor mSourceConfigurationEditor;
     private AuxDecoderConfigurationEditor mAuxDecoderConfigurationEditor;
     private EventLogConfigurationEditor mEventLogConfigurationEditor;
-    private TalkgroupValueChangeListener mTalkgroupValueChangeListener = new TalkgroupValueChangeListener();
+    private final TalkgroupValueChangeListener mTalkgroupValueChangeListener = new TalkgroupValueChangeListener();
-    private IntegerFormatter mDecimalFormatter = new IntegerFormatter(1, 65535);
+    private final IntegerFormatter mDecimalFormatter = new IntegerFormatter(1, 65535);
-    private HexFormatter mHexFormatter = new HexFormatter(1, 65535);
+    private final HexFormatter mHexFormatter = new HexFormatter(1, 65535);
 
     /**
      * Constructs an instance
@@ -162,12 +162,15 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
 
             Label talkgroupLabel = new Label("Talkgroup To Assign");
             GridPane.setHalignment(talkgroupLabel, HPos.RIGHT);
-            GridPane.setConstraints(talkgroupLabel, 6, 0);
+            GridPane.setConstraints(talkgroupLabel, 0, 1);
             gridPane.getChildren().add(talkgroupLabel);
 
-            GridPane.setConstraints(getTalkgroupField(), 7, 0);
+            GridPane.setConstraints(getTalkgroupField(), 1, 1);
             gridPane.getChildren().add(getTalkgroupField());
 
+            GridPane.setConstraints(getAudioFilterEnable(), 2, 1);
+            gridPane.getChildren().add(getAudioFilterEnable());
+
             mDecoderPane.setContent(gridPane);
 
             //Special handling - the pill button doesn't like to set a selected state if the pane is not expanded,
@@ -275,6 +278,22 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
         return mAuxDecoderConfigurationEditor;
     }
 
+    /**
+     * Toggle switch for enable/disable the audio filtering in the audio module.
+     * @return toggle switch.
+     */
+    private ToggleSwitch getAudioFilterEnable()
+    {
+        if(mAudioFilterEnable == null)
+        {
+            mAudioFilterEnable = new ToggleSwitch("High-Pass Audio Filter");
+            mAudioFilterEnable.setTooltip(new Tooltip("High-pass filter to remove DC offset and sub-audible signalling"));
+            mAudioFilterEnable.selectedProperty().addListener((observable, oldValue, newValue) -> modifiedProperty().set(true));
+        }
+
+        return mAudioFilterEnable;
+    }
+
     private SegmentedButton getBandwidthButton()
     {
         if(mBandwidthButton == null)
@@ -298,31 +317,27 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
             //decode configuration and we're unable to correctly set the bandwidth setting.  As a work
             //around, we'll listen for the toggles to be added and update them here.  This normally only
             //happens when we first instantiate the editor and load an item for editing the first time.
-            mBandwidthButton.getToggleGroup().getToggles().addListener(new ListChangeListener<Toggle>()
+            mBandwidthButton.getToggleGroup().getToggles().addListener((ListChangeListener<Toggle>)c ->
             {
-                @Override
+                //This change event happens when the toggles are added -- we don't need to inspect the change event
-                public void onChanged(Change<? extends Toggle> c)
+                if(getItem() != null && getItem().getDecodeConfiguration() instanceof DecodeConfigNBFM)
                 {
-                    //This change event happens when the toggles are added -- we don't need to inspect the change event
+                    //Capture current modified state so that we can reapply after adjusting control states
-                    if(getItem() != null && getItem().getDecodeConfiguration() instanceof DecodeConfigNBFM)
+                    boolean modified = modifiedProperty().get();
+
+                    DecodeConfigNBFM config = (DecodeConfigNBFM)getItem().getDecodeConfiguration();
+                    DecodeConfigNBFM.Bandwidth bandwidth = config.getBandwidth();
+                    if(bandwidth == null)
                     {
-                        //Capture current modified state so that we can reapply after adjusting control states
+                        bandwidth = DecodeConfigNBFM.Bandwidth.BW_12_5;
-                        boolean modified = modifiedProperty().get();
-
-                        DecodeConfigNBFM config = (DecodeConfigNBFM)getItem().getDecodeConfiguration();
-                        DecodeConfigNBFM.Bandwidth bandwidth = config.getBandwidth();
-                        if(bandwidth == null)
-                        {
-                            bandwidth = DecodeConfigNBFM.Bandwidth.BW_12_5;
-                        }
-
-                        for(Toggle toggle: getBandwidthButton().getToggleGroup().getToggles())
-                        {
-                            toggle.setSelected(toggle.getUserData() == bandwidth);
-                        }
-
-                        modifiedProperty().set(modified);
                     }
+
+                    for(Toggle toggle: getBandwidthButton().getToggleGroup().getToggles())
+                    {
+                        toggle.setSelected(toggle.getUserData() == bandwidth);
+                    }
+
+                    modifiedProperty().set(modified);
                 }
             });
         }
@@ -449,6 +464,8 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
             mSquelchTextFormatter.setValue(decodeConfigNBFM.getSquelchThreshold());
             getSquelchAutoTrackSwitch().setDisable(false);
             getSquelchAutoTrackSwitch().setSelected(decodeConfigNBFM.isSquelchAutoTrack());
+            getAudioFilterEnable().setDisable(false);
+            getAudioFilterEnable().setSelected(decodeConfigNBFM.isAudioFilter());
         }
         else
         {
@@ -464,6 +481,8 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
             getSquelchThresholdField().setDisable(true);
             getSquelchAutoTrackSwitch().setDisable(true);
             getSquelchAutoTrackSwitch().setSelected(false);
+            getAudioFilterEnable().setDisable(true);
+            getAudioFilterEnable().setSelected(false);
         }
     }
 
@@ -500,6 +519,7 @@ public class NBFMConfigurationEditor extends ChannelConfigurationEditor
         config.setTalkgroup(talkgroup);
         config.setSquelchThreshold(mSquelchTextFormatter.getValue());
         config.setSquelchAutoTrack(getSquelchAutoTrackSwitch().isSelected());
+        config.setAudioFilter(getAudioFilterEnable().isSelected());
         getItem().setDecodeConfiguration(config);
     }
 

src/main/java/io/github/dsheirer/module/decode/DecoderFactory.java

@@ -105,6 +105,7 @@ public class DecoderFactory
 {
     private final static Logger mLog = LoggerFactory.getLogger(DecoderFactory.class);
     private static final double FM_CHANNEL_BANDWIDTH = 12500.0;
+    private static final boolean AUDIO_FILTER_ENABLE = true;
 
     /**
      * Returns a list of one primary decoder and any auxiliary decoders, as
@@ -246,14 +247,14 @@ public class DecoderFactory
     /**
      * Creates decoder modules for Passport decoder
      * @param channel configuration
-     * @param userPreferences reference
      * @param modules collection to add to
      * @param aliasList for the channel
+     * @param decodeConfig for the channel
      */
     private static void processPassport(Channel channel, List<Module> modules, AliasList aliasList, DecodeConfiguration decodeConfig) {
         modules.add(new PassportDecoder(decodeConfig));
         modules.add(new PassportDecoderState());
-        modules.add(new AudioModule(aliasList));
+        modules.add(new AudioModule(aliasList, AUDIO_FILTER_ENABLE));
         if(channel.getSourceConfiguration().getSourceType() == SourceType.TUNER)
         {
             modules.add(new FMDemodulatorModule(FM_CHANNEL_BANDWIDTH));
@@ -262,10 +263,12 @@ public class DecoderFactory
 
     /**
      * Creates decoder modules for MPT-1327 decoder
+     * @param channelMapModel to use in calculating traffic channel frequencies
      * @param channel configuration
-     * @param userPreferences reference
      * @param modules collection to add to
      * @param aliasList for the channel
+     * @param channelType for control or traffic
+     * @param decodeConfig configuration
      */
     private static void processMPT1327(ChannelMapModel channelMapModel, Channel channel, List<Module> modules, AliasList aliasList, ChannelType channelType, DecodeConfigMPT1327 decodeConfig) {
         DecodeConfigMPT1327 mptConfig = decodeConfig;
@@ -279,7 +282,7 @@ public class DecoderFactory
         // not create a new segment if the processing chain finishes a bit after
         // actual call timeout.
         long maxAudioSegmentLengthMillis = (callTimeoutMilliseconds + 5000);
-        modules.add(new AudioModule(aliasList, AbstractAudioModule.DEFAULT_TIMESLOT, maxAudioSegmentLengthMillis));
+        modules.add(new AudioModule(aliasList, AbstractAudioModule.DEFAULT_TIMESLOT, maxAudioSegmentLengthMillis, AUDIO_FILTER_ENABLE));
 
         SourceType sourceType = channel.getSourceConfiguration().getSourceType();
         if(sourceType == SourceType.TUNER || sourceType == SourceType.TUNER_MULTIPLE_FREQUENCIES)
@@ -312,14 +315,14 @@ public class DecoderFactory
     /**
      * Creates decoder modules for LTR-Net decoder
      * @param channel configuration
-     * @param userPreferences reference
      * @param modules collection to add to
      * @param aliasList for the channel
+     * @param decodeConfig for the channel
      */
     private static void processLTRNet(Channel channel, List<Module> modules, AliasList aliasList, DecodeConfigLTRNet decodeConfig) {
         modules.add(new LTRNetDecoder(decodeConfig));
         modules.add(new LTRNetDecoderState());
-        modules.add(new AudioModule(aliasList));
+        modules.add(new AudioModule(aliasList, AUDIO_FILTER_ENABLE));
         if(channel.getSourceConfiguration().getSourceType() == SourceType.TUNER)
         {
             modules.add(new FMDemodulatorModule(FM_CHANNEL_BANDWIDTH));
@@ -329,15 +332,15 @@ public class DecoderFactory
     /**
      * Creates decoder modules for LTR decoder
      * @param channel configuration
-     * @param userPreferences reference
      * @param modules collection to add to
      * @param aliasList for the channel
+     * @param decodeConfig for the channel
      */
     private static void processLTRStandard(Channel channel, List<Module> modules, AliasList aliasList, DecodeConfigLTRStandard decodeConfig) {
         MessageDirection direction = decodeConfig.getMessageDirection();
         modules.add(new LTRStandardDecoder(direction));
         modules.add(new LTRStandardDecoderState());
-        modules.add(new AudioModule(aliasList));
+        modules.add(new AudioModule(aliasList, AUDIO_FILTER_ENABLE));
         if(channel.getSourceConfiguration().getSourceType() == SourceType.TUNER)
         {
             modules.add(new FMDemodulatorModule(FM_CHANNEL_BANDWIDTH));
@@ -347,9 +350,9 @@ public class DecoderFactory
     /**
      * Creates decoder modules for Narrow Band FM decoder
      * @param channel configuration
-     * @param userPreferences reference
      * @param modules collection to add to
      * @param aliasList for the channel
+     * @param decodeConfig for the channel
      */
     private static void processNBFM(Channel channel, List<Module> modules, AliasList aliasList, DecodeConfiguration decodeConfig)
     {
@@ -362,15 +365,15 @@ public class DecoderFactory
         DecodeConfigNBFM decodeConfigNBFM = (DecodeConfigNBFM)decodeConfig;
         modules.add(new NBFMDecoder(decodeConfigNBFM));
         modules.add(new NBFMDecoderState(channel.getName(), decodeConfigNBFM));
-        modules.add(new AudioModule(aliasList, 0, 60000));
+        modules.add(new AudioModule(aliasList, 0, 60000, decodeConfigNBFM.isAudioFilter()));
     }
 
     /**
      * Creates decoder modules for AM decoder
      * @param channel configuration
-     * @param userPreferences reference
      * @param modules collection to add to
      * @param aliasList for the channel
+     * @param decodeConfig for the channel
      */
     private static void processAM(Channel channel, List<Module> modules, AliasList aliasList, DecodeConfiguration decodeConfig) {
 
@@ -383,7 +386,7 @@ public class DecoderFactory
         DecodeConfigAM decodeConfigAM = (DecodeConfigAM) decodeConfig;
         modules.add(new AMDecoder(decodeConfigAM));
         modules.add(new AMDecoderState(channel.getName(), decodeConfigAM));
-        modules.add(new AudioModule(aliasList, 0, 60000));
+        modules.add(new AudioModule(aliasList, 0, 60000, AUDIO_FILTER_ENABLE));
     }
 
     /**
@@ -575,7 +578,7 @@ public class DecoderFactory
             case P25_PHASE2:
                 return new DecodeConfigP25Phase2();
             default:
-                throw new IllegalArgumentException("DecodeConfigFactory - unknown decoder type [" + decoder.toString() + "]");
+                throw new IllegalArgumentException("DecodeConfigFactory - unknown decoder type [" + decoder + "]");
         }
     }
 

src/main/java/io/github/dsheirer/module/decode/nbfm/DecodeConfigNBFM.java

@@ -29,6 +29,11 @@ import io.github.dsheirer.source.tuner.channel.ChannelSpecification;
  */
 public class DecodeConfigNBFM extends DecodeConfigAnalog
 {
+    private boolean mAudioFilter = true;
+
+    /**
+     * Constructs an instance
+     */
     public DecodeConfigNBFM()
     {
     }
@@ -62,4 +67,23 @@ public class DecodeConfigNBFM extends DecodeConfigAnalog
                 throw new IllegalArgumentException("Unrecognized FM bandwidth value: " + getBandwidth());
         }
     }
+
+    /**
+     * Indicates if the user wants the demodulated audio to be high-pass filtered.
+     * @return enable status, defaults to true.
+     */
+    @JacksonXmlProperty(isAttribute = true, localName = "audioFilter")
+    public boolean isAudioFilter()
+    {
+        return mAudioFilter;
+    }
+
+    /**
+     * Sets the enabled state of high-pass filtering of the demodulated audio.
+     * @param audioFilter to true to enable high-pass filtering.
+     */
+    public void setAudioFilter(boolean audioFilter)
+    {
+        mAudioFilter = audioFilter;
+    }
 }