Refactoring to use COMPLEX and REAL sample terms throughout

src/dsp/agc/ComplexAutomaticGainControl.java

@@ -0,0 +1,198 @@
+package dsp.agc;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import sample.Listener;
+import sample.Provider;
+import sample.complex.ComplexSample;
+import buffer.ComplexCircularBuffer;
+import buffer.DoubleCircularBuffer;
+
+/**
+ * Automatic Gain Control (AGC) for complex samples at 48000 sample rate.
+ */
+public class ComplexAutomaticGainControl implements Listener<ComplexSample>,
+												    Provider<ComplexSample>
+{
+	private static final double SAMPLE_RATE = 48000;
+	
+	/* Signal delay line - time delay in seconds */
+	private static final double DELAY_TIME_CONSTANT = 0.015;
+
+	/* Peak detector window - time delay in seconds */
+	private static final double WINDOW_TIME_CONSTANT = 0.018;
+
+	/* Attack time constants in seconds */
+	private static final double ATTACK_RISE_TIME_CONSTANT = 0.002;
+	private static final double ATTACK_FALL_TIME_CONSTANT = 0.005;
+
+	private static final double ATTACK_RISE_ALPHA = 1.0 - 
+		Math.exp( -1.0 / SAMPLE_RATE * ATTACK_RISE_TIME_CONSTANT );
+
+	private static final double ATTACK_FALL_ALPHA = 1.0 - 
+		Math.exp( -1.0 / SAMPLE_RATE * ATTACK_FALL_TIME_CONSTANT );
+
+	/* AGC decay value in milliseconds (20 to 5000) */
+	private static final double DECAY = 200;
+	
+	/* Ratio between rise and fall times of decay time constants - adjust for
+	 * best action with SSB */
+	private static final double DECAY_RISEFALL_RATIO = 0.3;
+
+	private static final double DECAY_RISE_ALPHA = 1.0 - 
+		Math.exp( -1.0 / ( SAMPLE_RATE * DECAY * .001 * DECAY_RISEFALL_RATIO ) );
+
+	private static final double DECAY_FALL_ALPHA = 1.0 - 
+		Math.exp( -1.0 / ( SAMPLE_RATE * DECAY * .001 ) );
+
+	/* Hang timer release decay time constant in seconds */
+	private static final double RELEASE_TIME_CONSTANT = 0.05;
+
+	/* Specifies the AGC Knee in dB if AGC is active (nominal range -160 to 0 dB) */
+	private static final double THRESHOLD = -100;
+
+	/* Limit output to about 3db of maximum */
+	private static final double AGC_OUT_SCALE = 0.7;
+
+	/* Keep max input and output the same */
+	private static final double MAX_AMPLITUDE = 32767.0; //1.0;
+	private static final double MAX_MANUAL_AMPLITUDE = 32767.0; //1.0;
+	
+	/* Specifies AGC manual gain in dB if AGC is not active ( 0 to 100 dB) */
+	private static final double MANUAL_GAIN = 0.0;
+
+	private static final double MANUAL_AGC_GAIN = MAX_MANUAL_AMPLITUDE * 
+			Math.pow( 10.0, MANUAL_GAIN / 20.0 );
+
+	/* Specifies dB reduction in output at knee from max output level (0 - 10dB) */
+	private static final double SLOPE_FACTOR = 2.0;
+
+	private static final double KNEE = THRESHOLD / 20.0;
+
+	private static final double GAIN_SLOPE = SLOPE_FACTOR / 100.0;
+
+	private static final double FIXED_GAIN = AGC_OUT_SCALE * 
+			Math.pow( 10.0, KNEE * ( GAIN_SLOPE - 1.0 ) );
+	
+	/* Constant for calc log() so that a value of 0 magnitude = -8 */
+	private static final double MIN_CONSTANT = 3.2767E-4;
+	
+	private AtomicBoolean mAGCEnabled = new AtomicBoolean( true );
+	
+	private double mPeakMagnitude = 0.0;
+	private double mAttackAverage = 0.0;
+	private double mDecayAverage = 0.0;
+	
+	private ComplexCircularBuffer mDelayBuffer = 
+		new ComplexCircularBuffer( (int)( SAMPLE_RATE * DELAY_TIME_CONSTANT ) );
+	private DoubleCircularBuffer mMagnitudeBuffer = 
+		new DoubleCircularBuffer( (int)( SAMPLE_RATE * WINDOW_TIME_CONSTANT ) );
+	
+	private Listener<ComplexSample> mListener;
+	
+	public ComplexAutomaticGainControl()
+	{
+	}
+
+	@Override
+    public void receive( ComplexSample currentSample )
+    {
+		ComplexSample delayedSample = mDelayBuffer.get( currentSample );
+
+		double gain = MANUAL_AGC_GAIN;
+		
+		if( mAGCEnabled.get() )
+		{
+			float max = currentSample.maximumAbsolute();
+
+			double currentMagnitude = Math.log10( max + MIN_CONSTANT ) - 
+							   Math.log10( MAX_AMPLITUDE );
+
+			double delayedMagnitude = mMagnitudeBuffer.get( currentMagnitude );
+			
+			if( currentMagnitude > mPeakMagnitude )
+			{
+				/* Use current magnitude as peak if it's larger */
+				mPeakMagnitude = currentMagnitude;
+			}
+			else if( delayedMagnitude == mPeakMagnitude )
+			{
+				/* If delayed magnitude is the current peak, then find a new peak */
+				mPeakMagnitude = mMagnitudeBuffer.max();
+			}
+
+			/* Exponential decay mode */
+			if( mPeakMagnitude > mAttackAverage )
+			{
+				mAttackAverage = ( ( 1.0 - ATTACK_RISE_ALPHA ) * mAttackAverage ) +
+						         ( ATTACK_RISE_ALPHA * mPeakMagnitude );
+			}
+			else
+			{
+				mAttackAverage = ( ( 1.0 - ATTACK_FALL_ALPHA ) * mAttackAverage ) +
+				         ( ATTACK_FALL_ALPHA * mPeakMagnitude );
+			}
+			
+			if( mPeakMagnitude > mDecayAverage )
+			{
+				mDecayAverage = ( ( 1.0 - DECAY_RISE_ALPHA ) * mDecayAverage ) + 
+						        ( DECAY_RISE_ALPHA * mPeakMagnitude );
+			}
+			else
+			{
+				mDecayAverage = ( ( 1.0 - DECAY_FALL_ALPHA ) * mDecayAverage ) + 
+				        ( DECAY_RISE_ALPHA * mPeakMagnitude );
+			}
+
+			double magnitude = ( mAttackAverage > mDecayAverage ) ? 
+								 mAttackAverage : mDecayAverage;
+
+			if( magnitude < KNEE )
+			{
+				gain = FIXED_GAIN;
+			}
+			else
+			{
+				gain = AGC_OUT_SCALE * Math.pow( 10.0, 
+						magnitude * ( GAIN_SLOPE - 1.0 ) );
+			}
+			
+		}
+
+		delayedSample.multiply( (float)gain );
+		
+		if( mListener != null )
+		{
+			mListener.receive( delayedSample );
+		}
+    }
+	
+	/**
+	 * Enables or disables Automatic Gain Control (AGC).
+	 */
+	public void setAGCEnabled( boolean enabled )
+	{
+		mAGCEnabled.set( enabled );
+	}
+
+	/**
+	 * Indicates if AGC is enabled
+	 * @return true=AGC, false=MANUAL GAIN
+	 */
+	public boolean isAGCEnabled()
+	{
+		return mAGCEnabled.get();
+	}
+
+	@Override
+    public void setListener( Listener<ComplexSample> listener )
+    {
+		mListener = listener;
+    }
+
+	@Override
+    public void removeListener( Listener<ComplexSample> listener )
+    {
+		mListener = null;
+    }
+}