Compute the tail time for an IIRFilter from its coefficients

third_party/WebKit/Source/platform/audio/IIRFilter.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IIRFilter_h
 #define IIRFilter_h
 
 #include "platform/PlatformExport.h"
 #include "platform/audio/AudioArray.h"
 #include "platform/wtf/Vector.h"
@@ skipping 12 matching lines @@
 
   void Process(const float* source_p, float* dest_p, size_t frames_to_process);
 
   void Reset();
 
   void GetFrequencyResponse(int n_frequencies,
                             const float* frequency,
                             float* mag_response,
                             float* phase_response);
 
+  // Compute the tail time of the IIR filter
+  double TailTime(double sample_rate);
+
+  // Reset the internal state of the IIR filter to the initial state.
+  void ResetState();
+
  private:
   // Filter memory
   //
   // For simplicity, we assume |m_xBuffer| and |m_yBuffer| have the same length,
   // and the length is a power of two.  Since the number of coefficients has a
   // fixed upper length, the size of xBuffer and yBuffer is fixed. |m_xBuffer|
   // holds the old input values and |m_yBuffer| holds the old output values
   // needed to compute the new output value.
   //
   // m_yBuffer[m_bufferIndex] holds the most recent output value, say, y[n].
@@ skipping 11 matching lines @@
 
   // Coefficients of the IIR filter.  To minimize storage, these point to the
   // arrays given in the constructor.
   const AudioDoubleArray* feedback_;
   const AudioDoubleArray* feedforward_;
 };
 
 }  // namespace blink
 
 #endif  // IIRFilter_h