Compute tail time from Biquad coefficients

third_party/WebKit/Source/modules/webaudio/BiquadDSPKernel.h

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 22 matching lines @@
 namespace blink {
 
 class BiquadProcessor;
 
 // BiquadDSPKernel is an AudioDSPKernel and is responsible for filtering one
 // channel of a BiquadProcessor using a Biquad object.
 
 class BiquadDSPKernel final : public AudioDSPKernel {
  public:
   explicit BiquadDSPKernel(BiquadProcessor* processor)
-      : AudioDSPKernel(processor) {}
+      : AudioDSPKernel(processor),
+        tail_time_(std::numeric_limits<double>::infinity()) {}
 
   // AudioDSPKernel
   void Process(const float* source,
                float* dest,
                size_t frames_to_process) override;
   void Reset() override { biquad_.Reset(); }
 
   // Get the magnitude and phase response of the filter at the given
   // set of frequencies (in Hz). The phase response is in radians.
   void GetFrequencyResponse(int n_frequencies,
@@ skipping 14 matching lines @@
   // dezippering is used to slowly change the parameters.
   void UpdateCoefficientsIfNecessary(int);
   // Update the biquad cofficients with the given parameters
   void UpdateCoefficients(int,
                           const float* frequency,
                           const float* q,
                           const float* gain,
                           const float* detune);
 
  private:
+  // Compute the tail time using the BiquadFilter coefficients at
+  // index |coef_index|.
+  void UpdateTailTime(int coef_index);
+
   // Synchronize process() with getting and setting the filter coefficients.
   mutable Mutex process_lock_;
+
+  // The current tail time for biquad filter.
+  double tail_time_;
 };
 
 }  // namespace blink
 
 #endif  // BiquadDSPKernel_h