Added function to get duration ratio between the original input and processed output tracks.

include/SoundTouch.h

@@ -259,6 +259,24 @@ public:
     /// Sets sample rate.
     void setSampleRate(uint srate);
 
+    /// Get ratio between input and output audio durations, useful for calculating
+    /// processed output duration: if you'll process a stream of N samples, then 
+    /// you can expect to get out N * getInputOutputSampleRatio() samples.
+    ///
+    /// This ratio will give accurate target duration ratio for a full audio track, 
+    /// given that the the whole track is processed with same processing parameters.
+    /// 
+    /// If this ratio is applied to calculate intermediate offsets inside a processing
+    /// stream, then this ratio is approximate and can deviate +- some tens of milliseconds 
+    /// from ideal offset, yet by end of the audio stream the duration ratio will become
+    /// exact.
+    ///
+    /// Example: if processing with parameters "-tempo=15 -pitch=-3", the function
+    /// will return value 0.8695652... Now, if processing an audio stream whose duration
+    /// is exactly one million audio samples, then you can expect the processed 
+    /// output duration  be 0.869565 * 1000000 = 869565 samples.
+    double getInputOutputSampleRatio();
+
     /// Flushes the last samples from the processing pipeline to the output.
     /// Clears also the internal processing buffers.
     //

source/SoundTouch/RateTransposer.cpp

@@ -211,7 +211,7 @@ int RateTransposer::isEmpty() const
 /// Return approximate initial input-output latency
 int RateTransposer::getLatency() const
 {
-	return (bUseAAFilter) ? pAAFilter->getLength() : 0;
+    return (bUseAAFilter) ? pAAFilter->getLength() : 0;
 }
 
 

source/SoundTouch/RateTransposer.h

@@ -172,6 +172,9 @@ public:
 
     /// Returns nonzero if there aren't any samples available for outputting.
     int isEmpty() const;
+
+    /// Return approximate initial input-output latency
+    int getLatency() const;
 };
 
 }

source/SoundTouch/SoundTouch.cpp

@@ -475,7 +475,6 @@ int SoundTouch::getSetting(int settingId) const
             return size;
         }
 
-
         case SETTING_NOMINAL_OUTPUT_SEQUENCE :
         {
             int size = pTDStretch->getOutputBatchSize();
@@ -514,6 +513,7 @@ int SoundTouch::getSetting(int settingId) const
 }
 
 
+
 // Clears all the samples in the object's output and internal processing
 // buffers.
 void SoundTouch::clear()
@@ -567,3 +567,12 @@ uint SoundTouch::receiveSamples(uint maxSamples)
     samplesOutput += (long)ret;
     return ret;
 }
+
+
+/// Get ratio between input and output audio durations, useful for calculating
+/// processed output duration: if you'll process a stream of N samples, then 
+/// you can expect to get out N * getInputOutputSampleRatio() samples.
+double SoundTouch::getInputOutputSampleRatio()
+{
+    return 1.0 / (tempo * rate);
+}