#1761 DMR decoder supports Hytera Tier 3 UTF-16 Talker Alias & new Traffic Channel Talker Status CSBKO 47. Implements a tracking feature to detect when vendors are playing games using non-standard CSBK CRC mask values by tracking when a non-standard mask value is consistently detected and applying that mask when the initial CRC check fails.

src/main/java/io/github/dsheirer/bits/BinaryMessage.java

@@ -20,6 +20,7 @@ package io.github.dsheirer.bits;
 
 import io.github.dsheirer.edac.CRC;
 import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
 import java.util.BitSet;
 import org.apache.commons.lang3.Validate;
 import org.apache.commons.math3.util.FastMath;
@@ -1278,7 +1279,7 @@ public class BinaryMessage extends BitSet
             bytes[x] = getByte(CHARACTER_8_BIT, x * 8 + offset);
         }
 
-        return new String(bytes);
+        return new String(bytes, Charset.forName("UTF-16"));
     }
 
     /**

src/main/java/io/github/dsheirer/edac/CRCDMR.java

@@ -1,18 +1,21 @@
-/*******************************************************************************
+/*
- * sdr-trunk
+ * *****************************************************************************
- * Copyright (C) 2014-2018 Dennis Sheirer
+ * Copyright (C) 2014-2023 Dennis Sheirer
  *
- * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * This program is free software: you can redistribute it and/or modify
- * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * it under the terms of the GNU General Public License as published by
- * later version.
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
  *
- * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * This program is distributed in the hope that it will be useful,
- * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License  along with this program.
+ * You should have received a copy of the GNU General Public License
- * If not, see <http://www.gnu.org/licenses/>
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
- *
+ * ****************************************************************************
- ******************************************************************************/
+ */
 package io.github.dsheirer.edac;
 
 import io.github.dsheirer.bits.BinaryMessage;
@@ -177,6 +180,28 @@ public class CRCDMR
         return 2;
     }
 
+    /**
+     * Calculates the residual CRC value using a mask of zero which should identify the mask value when an alternate
+     * mask value is employed.
+     * @param message to be checked
+     * @param messageStart location
+     * @param crcStart location
+     * @return residual CRC check value.
+     */
+    public static int calculateResidual(CorrectedBinaryMessage message, int messageStart, int crcStart)
+    {
+        int calculated = 0; //Starting value
+
+        /* Iterate the set bits and XOR running checksum with lookup value */
+        for(int i = message.nextSetBit(messageStart); i >= messageStart && i < crcStart; i = message.nextSetBit(i + 1))
+        {
+            calculated ^= CCITT_80_CHECKSUMS[i - messageStart];
+        }
+
+        int checksum = getIntChecksum(message, crcStart, 16);
+        return calculated ^ checksum;
+    }
+
     /**
      * Error detection for CRC-9 protected Confirmed Packet Data blocks.  These
      * data blocks have a slightly complicated structure because the checksum

src/main/java/io/github/dsheirer/module/decode/dmr/DMRDecoder.java

@@ -42,8 +42,11 @@ import io.github.dsheirer.sample.complex.IComplexSamplesListener;
 import io.github.dsheirer.source.ISourceEventListener;
 import io.github.dsheirer.source.ISourceEventProvider;
 import io.github.dsheirer.source.SourceEvent;
+import io.github.dsheirer.source.wave.ComplexWaveSource;
+import java.io.File;
 import java.nio.ByteBuffer;
 import java.util.HashMap;
+import java.util.Iterator;
 import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -332,4 +335,38 @@ public class DMRDecoder extends FeedbackDecoder implements ISourceEventListener,
     {
         return DMRDecoder.this;
     }
+
+    public static void main(String[] args)
+    {
+        File file = new File("/home/denny/Downloads/TIII,HYT414.585000,.wav");
+
+        try
+        {
+            ComplexWaveSource source = new ComplexWaveSource(file);
+            source.open();
+            System.out.println("Source Sample Rate: " + source.getSampleRate());
+            DMRDecoder decoder = new DMRDecoder(new DecodeConfigDMR());
+            decoder.setMessageListener(message -> System.out.println("TS:" + message.getTimeslot() + " " + message));
+            source.setListener(iNativeBuffer -> {
+                Iterator<ComplexSamples> it = iNativeBuffer.iterator();
+                while(it.hasNext())
+                {
+                    ComplexSamples samples = it.next();
+                    decoder.receive(samples);
+                }
+            });
+            decoder.setSampleRate(source.getSampleRate());
+            decoder.start();
+            source.start();
+
+            while(true)
+            {
+                source.next(65535);
+            }
+        }
+        catch(Exception e)
+        {
+            e.printStackTrace();
+        }
+    }
 }

src/main/java/io/github/dsheirer/module/decode/dmr/DMRDecoderState.java

@@ -42,6 +42,7 @@ import io.github.dsheirer.module.decode.dmr.identifier.DMRTalkgroup;
 import io.github.dsheirer.module.decode.dmr.message.DMRMessage;
 import io.github.dsheirer.module.decode.dmr.message.data.DataMessage;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.CSBKMessage;
+import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraTrafficChannelTalkerStatus;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.motorola.CapacityMaxAloha;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.motorola.CapacityPlusNeighbors;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.motorola.CapacityPlusSiteStatus;
@@ -708,7 +709,22 @@ public class DMRDecoderState extends TimeslotDecoderState
             case HYTERA_08_ANNOUNCEMENT:
             case HYTERA_68_ANNOUNCEMENT:
             case HYTERA_68_XPT_SITE_STATE:
-
+                break;
+            case HYTERA_08_TRAFFIC_CHANNEL_TALKER_STATUS:
+                if(csbk instanceof HyteraTrafficChannelTalkerStatus status)
+                {
+                    if(status.isChannelActive())
+                    {
+                        getIdentifierCollection().update(status.getIdentifiers());
+                        updateCurrentCall(DecodeEventType.CALL_GROUP, "HYTERA TIER 3 CALL", status.getTimestamp());
+                    }
+                    else
+                    {
+                        getIdentifierCollection().remove(Role.FROM);
+                        getIdentifierCollection().update(status.getDestinationRadio());
+                    }
+                }
+                break;
             case MOTOROLA_CAPPLUS_NEIGHBOR_REPORT:
                 if(csbk instanceof CapacityPlusNeighbors)
                 {

src/main/java/io/github/dsheirer/module/decode/dmr/DMRMessageProcessor.java

@@ -27,6 +27,7 @@ import io.github.dsheirer.module.decode.dmr.message.CACH;
 import io.github.dsheirer.module.decode.dmr.message.DMRBurst;
 import io.github.dsheirer.module.decode.dmr.message.data.IDLEMessage;
 import io.github.dsheirer.module.decode.dmr.message.data.block.DataBlock;
+import io.github.dsheirer.module.decode.dmr.message.data.csbk.CSBKMessage;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.standard.Aloha;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.standard.Preamble;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.standard.announcement.Announcement;
@@ -71,6 +72,7 @@ public class DMRMessageProcessor implements Listener<IMessage>
     private TalkerAliasAssembler mTalkerAliasAssembler = new TalkerAliasAssembler();
     private Listener<IMessage> mMessageListener;
     private Map<Integer,TimeslotFrequency> mTimeslotFrequencyMap = new TreeMap<>();
+    private DmrCrcMaskManager mCrcMaskManager = new DmrCrcMaskManager();
 
     /**
      * Constructs an instance
@@ -93,6 +95,17 @@ public class DMRMessageProcessor implements Listener<IMessage>
     @Override
     public void receive(IMessage message)
     {
+        if(message == null)
+        {
+            return;
+        }
+
+        //Detect and correct messages employing an alternate CRC mask pattern.
+        if(!message.isValid() && message instanceof CSBKMessage csbk)
+        {
+            mCrcMaskManager.check(csbk);
+        }
+
         if(message instanceof FullLCMessage flc)
         {
             if(flc.getTimeslot() == 1)

src/main/java/io/github/dsheirer/module/decode/dmr/DmrCrcMaskManager.java

@@ -0,0 +1,232 @@
+/*
+ * *****************************************************************************
+ * Copyright (C) 2014-2023 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * ****************************************************************************
+ */
+
+package io.github.dsheirer.module.decode.dmr;
+
+import io.github.dsheirer.edac.CRCDMR;
+import io.github.dsheirer.module.decode.dmr.message.data.csbk.CSBKMessage;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Date;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Manages alternate CRC masks that may be employed in a system.
+ */
+public class DmrCrcMaskManager
+{
+    private Logger LOGGER = LoggerFactory.getLogger(DmrCrcMaskManager.class);
+    private Map<Integer, ResidualCrcMaskTracker> mCsbkResidualTrackerMap = new TreeMap<>();
+    private int mDominantMask = 0;
+
+    /**
+     * Constructs an instance
+     */
+    public DmrCrcMaskManager()
+    {
+    }
+
+    /**
+     * Creates a deep copy (ie clone) of all tracked values
+     * @return list of tracker clones.
+     */
+    public List<ResidualCrcMaskTracker> cloneTrackers()
+    {
+        List<ResidualCrcMaskTracker>trackers = new ArrayList<>();
+        for(ResidualCrcMaskTracker tracker: mCsbkResidualTrackerMap.values())
+        {
+            trackers.add(tracker.clone());
+        }
+
+        return trackers;
+    }
+
+    /**
+     * Logs the current tracked CRC values and counts.
+     */
+    public void log()
+    {
+        List<ResidualCrcMaskTracker> trackers = new ArrayList<>(mCsbkResidualTrackerMap.values());
+        Collections.sort(trackers);
+
+        StringBuilder sb = new StringBuilder();
+        sb.append("DMR CRC Mask Manager - Current Tracked Values\n");
+        for(ResidualCrcMaskTracker tracker: trackers)
+        {
+            sb.append("\tTracked Value: ").append(String.format("0x%04X", tracker.getTrackedValue()));
+            sb.append(" Count:").append(tracker.getCount());
+            sb.append(" Last Observed: " + new Date(tracker.getLastUpdated())).append("\n");
+        }
+
+        LOGGER.info(sb.toString());
+    }
+
+    /**
+     * Checks the CSBK message that has a failed CRC checksum to detect if an alternate CRC mask value is employed and
+     * if so, attempts to correct the message by using the alternate mask value once the alternate mask value is
+     * detected to be used consistently enough.
+     * @param csbk to re-check.
+     */
+    public void check(CSBKMessage csbk)
+    {
+        if(!csbk.isValid())
+        {
+            int residual = CRCDMR.calculateResidual(csbk.getMessage(), 0, 80);
+
+            if(mCsbkResidualTrackerMap.containsKey(residual))
+            {
+                mCsbkResidualTrackerMap.get(residual).increment();
+            }
+            else
+            {
+                mCsbkResidualTrackerMap.put(residual, new ResidualCrcMaskTracker(residual));
+            }
+
+            List<ResidualCrcMaskTracker> trackers = new ArrayList<>(mCsbkResidualTrackerMap.values());
+            Collections.sort(trackers);
+
+            if(trackers.size() > 5)
+            {
+                mCsbkResidualTrackerMap.remove(trackers.get(0).getTrackedValue());
+            }
+
+            if(trackers.size() > 0)
+            {
+                ResidualCrcMaskTracker dominant = trackers.get(trackers.size() - 1);
+
+                if(dominant.isValid())
+                {
+                    mDominantMask = dominant.getTrackedValue();
+                }
+            }
+
+            if(mDominantMask != 0)
+            {
+                csbk.checkCRC(mDominantMask);
+//
+//                if(csbk.isValid())
+//                {
+//                    LOGGER.info("CSBK fixed using alternate mask: " + Integer.toHexString(mDominantMask).toUpperCase());
+//                }
+            }
+        }
+    }
+
+    /**
+     * Residual CRC mask value tracker.  Tracks the number of observances of a residual CRC calculated value to detect
+     * when an alternate CRC mask pattern is employed and automatically correct CRC values for messages.
+     */
+    public class ResidualCrcMaskTracker implements Comparable<ResidualCrcMaskTracker>
+    {
+        private int mTrackedValue;
+        private int mCount;
+        private long mLastUpdated;
+
+        /**
+         * Constructs an instance for the specified residual, sets the count to one and sets the last update to now.
+         * @param residual value to track.
+         */
+        public ResidualCrcMaskTracker(int residual)
+        {
+            mTrackedValue = residual;
+            mCount = 1;
+            mLastUpdated = System.currentTimeMillis();
+        }
+
+        /**
+         * Create a deep copy of this instance.
+         * @return cloned instance.
+         */
+        public ResidualCrcMaskTracker clone()
+        {
+            ResidualCrcMaskTracker clone = new ResidualCrcMaskTracker(getTrackedValue());
+            clone.mCount = mCount;
+            clone.mLastUpdated = mLastUpdated;
+            return clone;
+        }
+
+        /**
+         * Count of number of times this residual has been observed.
+         * @return count
+         */
+        public int getCount()
+        {
+            return mCount;
+        }
+
+        /**
+         * Indicates that the residual value has been observed at least 3x times indicating that it is possibly valid.
+         * @return
+         */
+        public boolean isValid()
+        {
+            return mCount >= 3;
+        }
+
+        /**
+         * Timestamp when this value was last observed.
+         */
+        public long getLastUpdated()
+        {
+            return mLastUpdated;
+        }
+
+        /**
+         * Residual tracked value.
+         * @return residual
+         */
+        public int getTrackedValue()
+        {
+            return mTrackedValue;
+        }
+
+        public void increment()
+        {
+            mCount++;
+            //Prevent rollover by keeping value at max integer value.
+            if(mCount < 0)
+            {
+                mCount = Integer.MAX_VALUE;
+            }
+            mLastUpdated = System.currentTimeMillis();
+        }
+
+        /**
+         * Custom sort order by count and then by last updated timestamp.
+         * @param o the object to be compared.
+         * @return
+         */
+        @Override
+        public int compareTo(ResidualCrcMaskTracker o)
+        {
+            int comparison = Integer.compare(getCount(), o.getCount());
+
+            if(comparison == 0)
+            {
+                comparison = Long.compare(getLastUpdated(), o.getLastUpdated());
+            }
+
+            return comparison;
+        }
+    }
+}

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/csbk/CSBKMessage.java

@@ -1,7 +1,6 @@
 /*
- * ******************************************************************************
+ * *****************************************************************************
- * sdrtrunk
+ * Copyright (C) 2014-2023 Dennis Sheirer
- * Copyright (C) 2014-2020 Dennis Sheirer, Zhenyu Mao
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -15,7 +14,7 @@
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>
- * *****************************************************************************
+ * ****************************************************************************
  */
 package io.github.dsheirer.module.decode.dmr.message.data.csbk;
 
@@ -72,6 +71,17 @@ public abstract class CSBKMessage extends DataMessage
         setValid(correctedBitCount < 2);
     }
 
+    /**
+     * Checks CRC using an alternate mask value and sets the message valid flag according to the results.
+     */
+    public void checkCRC(int mask)
+    {
+        int correctedBitCount = CRCDMR.correctCCITT80(getMessage(), 0, 80, mask);
+
+        //Set message valid flag according to the corrected bit count for the CRC protected message
+        setValid(correctedBitCount < 2);
+    }
+
     /**
      * Checks crc for multi-block CSBK where the continuation block is an absolute channel parameters block
      *

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/csbk/CSBKMessageFactory.java

@@ -29,8 +29,8 @@ import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraAdjac
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraAloha;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraAnnouncement;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraCsbko44;
-import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraCsbko47;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraSmsAvailableNotification;
+import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraTrafficChannelTalkerStatus;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraXPTPreamble;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.hytera.HyteraXPTSiteState;
 import io.github.dsheirer.module.decode.dmr.message.data.csbk.motorola.CapacityMaxAloha;
@@ -250,8 +250,8 @@ public class CSBKMessageFactory
                 case HYTERA_08_CSBKO_44:
                     csbk = new HyteraCsbko44(pattern, message, cach, slotType, timestamp, timeslot);
                     break;
-                case HYTERA_08_CSBKO_47:
+                case HYTERA_08_TRAFFIC_CHANNEL_TALKER_STATUS:
-                    csbk = new HyteraCsbko47(pattern, message, cach, slotType, timestamp, timeslot);
+                    csbk = new HyteraTrafficChannelTalkerStatus(pattern, message, cach, slotType, timestamp, timeslot);
                     break;
                 case HYTERA_68_ACKNOWLEDGE:
                     csbk = new Hytera68Acknowledge(pattern, message, cach, slotType, timestamp, timeslot);

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/csbk/Opcode.java

@@ -93,7 +93,7 @@ public enum Opcode
     //CSBKO 44 & 47 observed on Tier3 interleaved in voice group call terminator sequence.  44 was continuously transmitted
     //and 47 was only transmitted 3x times in succession in the middle of the terminators and CSBKO 44 messages.
     HYTERA_08_CSBKO_44(Vendor.HYTERA_8, 44, "HYTERA 08 CSBKO 44"),
-    HYTERA_08_CSBKO_47(Vendor.HYTERA_8, 47, "HYTERA 08 CSBKO 47"),
+    HYTERA_08_TRAFFIC_CHANNEL_TALKER_STATUS(Vendor.HYTERA_8, 47, "HYTERA 08 CSBKO 47"),
 
     HYTERA_68_XPT_SITE_STATE(Vendor.HYTERA_68, 10, "HYTERA 68 XPT SITE STATE"),
     HYTERA_68_ALOHA(Vendor.HYTERA_68, 25, "HYTERA 68 ALOHA"),
@@ -201,7 +201,7 @@ public enum Opcode
      * Hytera opcodes
      */
     public static final EnumSet<Opcode> HYTERA = EnumSet.of(HYTERA_08_ACKNOWLEDGE, HYTERA_08_ANNOUNCEMENT,
-            HYTERA_08_CSBKO_44, HYTERA_08_CSBKO_47, HYTERA_68_XPT_SITE_STATE, HYTERA_68_ALOHA,
+            HYTERA_08_CSBKO_44, HYTERA_08_TRAFFIC_CHANNEL_TALKER_STATUS, HYTERA_68_XPT_SITE_STATE, HYTERA_68_ALOHA,
             HYTERA_68_ACKNOWLEDGE, HYTERA_68_ANNOUNCEMENT, HYTERA_68_XPT_PREAMBLE, HYTERA_68_CSBKO_62);
 
     /**

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/csbk/hytera/HyteraCsbko44.java

@@ -34,6 +34,9 @@ import java.util.List;
  * Analysis: ... this was transmitted on the Tier III traffic channel during call termination.  This CSBK was
  * interleaved with every other Terminator message, starting after the first 2x terminator messages.  This continued
  * through the final teardown which was 3x Clear messages.
+ *
+ * On a second example, there were 8 distinct configurations of this message that were repeated in-order, multiple times
+ * during the traffic channel shutdown ... a total of 51x of these messages were transmitted.
  */
 public class HyteraCsbko44 extends CSBKMessage
 {

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/csbk/hytera/HyteraTrafficChannelTalkerStatus.java

@@ -33,13 +33,14 @@ import java.util.List;
 /**
  * Hytera DMR Tier III - CSBKO 47 -
  *
- * Analysis: ... this was transmitted on the traffic channel while the mobile was at the end of a call, in the terminator
+ * Analysis: this message is transmitted three times at the beginning or end of a voice transmission and appears to
- * sequence.  Since this comes from the SMS gateway 16776906, I wonder if this is a traffic channel message waiting notification?
+ * indicate that the traffic channel continues active and signals the start/end of an active speaker.
  */
-public class HyteraCsbko47 extends CSBKMessage
+public class HyteraTrafficChannelTalkerStatus extends CSBKMessage
 {
     private static final int[] UNKNOWN_1 = new int[]{16, 17, 18, 19, 20, 21, 22, 23};
     private static final int[] UNKNOWN_2 = new int[]{24, 25, 26, 27, 28, 29, 30, 31};
+    private static final int TALKER_INACTIVE = 30;
     private static final int[] DESTINATION_RADIO = new int[]{32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
             49, 50, 51, 52, 53, 54, 55};
     private static final int[] SOURCE_RADIO = new int[]{56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72,
@@ -59,7 +60,7 @@ public class HyteraCsbko47 extends CSBKMessage
      * @param timestamp
      * @param timeslot
      */
-    public HyteraCsbko47(DMRSyncPattern syncPattern, CorrectedBinaryMessage message, CACH cach, SlotType slotType, long timestamp, int timeslot)
+    public HyteraTrafficChannelTalkerStatus(DMRSyncPattern syncPattern, CorrectedBinaryMessage message, CACH cach, SlotType slotType, long timestamp, int timeslot)
     {
         super(syncPattern, message, cach, slotType, timestamp, timeslot);
     }
@@ -79,17 +80,39 @@ public class HyteraCsbko47 extends CSBKMessage
         {
             sb.append(" RAS:").append(getBPTCReservedBits());
         }
-        sb.append(" HYTERA CSBKO=47  #########  UNKNOWN");
+        sb.append(" HYTERA TRAFFIC CHANNEL");
+        if(isChannelInactive())
+        {
+            sb.append(" NOW AVAILABLE - PREVIOUS TALKER:").append(getDestinationRadio());
+        }
+        else
+        {
+            sb.append(" IN USE - CURRENT TALKER:").append(getDestinationRadio());
+        }
         sb.append(" FM:").append(getSourceRadio());
-        sb.append(" TO:").append(getDestinationRadio());
         sb.append(" UNK1:").append(getUnknown1());
         sb.append(" UNK2:").append(getUnknown2());
-
         sb.append(" MSG:").append(getMessage().toHexString());
 
         return sb.toString();
     }
 
+    /**
+     * Indicates if the channel is inactive and available for use.
+     */
+    public boolean isChannelInactive()
+    {
+        return getMessage().get(TALKER_INACTIVE);
+    }
+
+    /**
+     * Indicates if the channel is active and in-use by the radio identifiers
+     */
+    public boolean isChannelActive()
+    {
+        return !isChannelInactive();
+    }
+
     /**
      * Addressed (ie TO) radio identifier
      * @return radio identifier
@@ -108,7 +131,6 @@ public class HyteraCsbko47 extends CSBKMessage
     {
         return getMessage().getHex(UNKNOWN_1, 2);
     }
-
     public String getUnknown2()
     {
         return getMessage().getHex(UNKNOWN_2, 2);

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/csbk/standard/Clear.java

@@ -118,7 +118,7 @@ public class Clear extends CSBKMessage implements ITimeslotFrequencyReceiver
             sb.append(" ENCRYPTED");
         }
 
-        sb.append(" CLEAR - RETURN TO ").append(getMoveToChannel());
+        sb.append(" CLEAR - RETURN TO").append(getMoveToChannel());
         sb.append(" FM:").append(getSourceRadio());
         sb.append(" TO:").append(getDestinationId());
         sb.append(" MSG:").append(getMessage().toHexString());

src/main/java/io/github/dsheirer/module/decode/dmr/message/data/lc/LCMessageFactory.java

@@ -109,6 +109,15 @@ public class LCMessageFactory
 
         LCOpcode opcode = FullLCMessage.getOpcode(message);
 
+        //Some Hytera Tier-3 systems use a zero-valued mask when the FLC is carried in the voice header or terminator
+        //and in the same transmission it uses the standard mask when carried across the voice frames. It doesn't make
+        //sense, but maybe it's a bug in their software implementation?
+        if(!valid && opcode == LCOpcode.FULL_STANDARD_GROUP_VOICE_CHANNEL_USER)
+        {
+            //Retry the RS(12,9,4) with a mask value of zero
+            valid = REED_SOLOMON_12_9_4_DMR.correctFullLinkControl(message, 0);
+        }
+
         FullLCMessage flc = null;
 
         switch(opcode)