Resolves #364.

The C4FM and LSM decoders were issuing a PLL reset with each new
channel that was allocated, causing any existing decoding channels to
be disrupted.  Decoding re-sync delays or inability to recapture the
 signal for decoding would likely result as the tuner's overall PPM
 caused misadjustment in the channel.

Resolved a NPE that was occurring in the FrequencyController for
sample rate changes.

src/main/java/io/github/dsheirer/dsp/filter/channelizer/PolyphaseChannelManager.java

@@ -416,7 +416,9 @@ public class PolyphaseChannelManager implements ISourceEventProcessor
             long centerFrequency = mChannelCalculator.getCenterFrequencyForIndexes(indexes);
 
             //If the indexes size is the same then update the current processor, otherwise create a new one
-            if(channelSource.getPolyphaseChannelOutputProcessor().getInputChannelCount() == indexes.size())
+            IPolyphaseChannelOutputProcessor outputProcessor = channelSource.getPolyphaseChannelOutputProcessor();
+
+            if(outputProcessor != null && outputProcessor.getInputChannelCount() == indexes.size())
             {
                 channelSource.getPolyphaseChannelOutputProcessor().setPolyphaseChannelIndices(indexes);
                 channelSource.setFrequency(centerFrequency);

src/main/java/io/github/dsheirer/dsp/psk/pll/CostasLoop.java

@@ -16,6 +16,8 @@
 package io.github.dsheirer.dsp.psk.pll;
 
 import io.github.dsheirer.sample.complex.Complex;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Costas Loop - phase locked loop designed to automatically synchronize to the incoming carrier frequency in order to
@@ -28,6 +30,8 @@ import io.github.dsheirer.sample.complex.Complex;
  */
 public class CostasLoop implements IPhaseLockedLoop
 {
+    private final static Logger mLog = LoggerFactory.getLogger(CostasLoop.class);
+
     public static final double TWO_PI = 2.0 * Math.PI;
 
     private Complex mCurrentVector = new Complex(0, 0);
@@ -37,7 +41,10 @@ public class CostasLoop implements IPhaseLockedLoop
     private double mDamping = Math.sqrt(2.0) / 2.0;
     private double mAlphaGain;
     private double mBetaGain;
-    private Tracking mTracking = Tracking.NORMAL;
+    private Tracking mTracking = Tracking.FASTEST;
+    private double mSymbolRate;
+    private double mSampleRate;
+    private int mCounter;
 
     /**
      * Costas Loop for tracking and correcting frequency error in a received carrier signal.
@@ -47,6 +54,8 @@ public class CostasLoop implements IPhaseLockedLoop
      */
     public CostasLoop(double sampleRate, double symbolRate)
     {
+        mSymbolRate = symbolRate;
+        mSampleRate = sampleRate;
         mMaximumLoopFrequency = TWO_PI * (symbolRate / 2.0) / sampleRate;
         updateLoopBandwidth();
     }
@@ -171,6 +180,16 @@ public class CostasLoop implements IPhaseLockedLoop
         {
             mLoopFrequency = -mMaximumLoopFrequency;
         }
+
+        //TODO: broadcast channel offset to the tuner to use in auto-adjusting tuner PPM
+//        mCounter++;
+//
+//        if(mCounter > (5 * mSymbolRate))
+//        {
+//            mCounter = 0;
+//            mLog.info("Current Costas Loop Frequency: " + mLoopFrequency + " [" +
+//                (int)(mSampleRate / TWO_PI * mLoopFrequency) + " Hz Offset] sample rate [" + mSampleRate + "]");
+//        }
     }
 
     @Override

src/main/java/io/github/dsheirer/module/decode/p25/P25DecoderC4FM.java

@@ -64,7 +64,7 @@ public class P25DecoderC4FM extends P25Decoder
         mBasebandFilter = new ComplexFIRFilter2(getBasebandFilter());
 
         mCostasLoop = new CostasLoop(getSampleRate(), getSymbolRate());
-        mCostasLoop.setTracking(Tracking.FAST);
+        mCostasLoop.setTracking(Tracking.FASTEST);
         mInterpolatingSampleBuffer = new InterpolatingSampleBuffer(getSamplesPerSymbol(), SAMPLE_COUNTER_GAIN);
 
         mQPSKDemodulator = new DQPSKDecisionDirectedDemodulator(mCostasLoop, mInterpolatingSampleBuffer);
@@ -161,11 +161,6 @@ public class P25DecoderC4FM extends P25Decoder
     {
         switch(sourceEvent.getEvent())
         {
-            case NOTIFICATION_FREQUENCY_CHANGE:
-            case NOTIFICATION_FREQUENCY_CORRECTION_CHANGE:
-            case NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE:
-                mCostasLoop.reset();
-                break;
             case NOTIFICATION_SAMPLE_RATE_CHANGE:
                 mCostasLoop.reset();
                 setSampleRate(sourceEvent.getValue().doubleValue());

src/main/java/io/github/dsheirer/module/decode/p25/P25DecoderLSM.java

@@ -115,14 +115,9 @@ public class P25DecoderLSM extends P25Decoder
     {
         switch(sourceEvent.getEvent())
         {
-            case NOTIFICATION_FREQUENCY_CHANGE:
-            case NOTIFICATION_FREQUENCY_CORRECTION_CHANGE:
-            case NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE:
-                mCostasLoop.reset();
-                break;
             case NOTIFICATION_SAMPLE_RATE_CHANGE:
-                mCostasLoop.reset();
                 setSampleRate(sourceEvent.getValue().doubleValue());
+                mCostasLoop.reset();
                 break;
         }
     }

src/main/java/io/github/dsheirer/source/tuner/frequency/FrequencyController.java

@@ -95,15 +95,18 @@ public class FrequencyController
      */
     public void setSampleRate(int sampleRate) throws SourceException
     {
-        if(!mLocked)
+        if(sampleRate != mSampleRate)
         {
-            mSampleRate = sampleRate;
+            if(!mLocked)
+            {
+                mSampleRate = sampleRate;
 
-            broadcastSampleRateChange();
-        }
-        else
-        {
-            mLog.warn("Cannot change sample rate while tuner is is LOCKED state.");
+                broadcastSampleRateChange();
+            }
+            else
+            {
+                mLog.warn("Cannot change sample rate while tuner is is LOCKED state.");
+            }
         }
     }