Add check for clipping and noise in loopback test.

qa/loopback/src/audio_analyzer.h

@@ -114,6 +114,12 @@ double PaQa_ComputePhaseDifference( double phase1, double phase2 );
  */
 double PaQa_MeasureArea( float *buffer, int numFrames, int stride  );
 
+/**
+ * Measure slope of the positive zero crossings.
+ */
+double PaQa_MeasureCrossingSlope( float *buffer, int numFrames );
+
+
 /**
  * Prepare an oscillator that can generate a sine tone for testing.
  */
@@ -156,6 +162,16 @@ double PaQa_CorrelateSine( PaQaRecording *recording, double frequency, double fr
 
 double PaQa_FindFirstMatch( PaQaRecording *recording, float *buffer, int numSamples, double tolerance  );
 
+/** 
+ * Estimate the original amplitude of a clipped sine wave by measuring
+ * its average slope at the zero crossings.
+ */
+double PaQa_MeasureSineAmplitudeBySlope( PaQaRecording *recording,
+										double frequency, double frameRate,
+										int startFrame, int numFrames );
+
+double PaQa_MeasureRootMeanSquare( float *buffer, int numFrames );
+
 /**
  * Compare the amplitudes of these two signals.
  * Return ratio of recorded signal over buffer signal.