third_party/WebKit/Source/platform/audio/HRTFPanner.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
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * DAMAGE.
 */

#ifndef HRTFPanner_h
#define HRTFPanner_h

#include "platform/audio/AudioDelayDSPKernel.h"
#include "platform/audio/FFTConvolver.h"
#include "platform/audio/HRTFDatabaseLoader.h"
#include "platform/audio/Panner.h"

namespace blink {

class PLATFORM_EXPORT HRTFPanner final : public Panner {
 public:
  HRTFPanner(float sampleRate, HRTFDatabaseLoader*);
  ~HRTFPanner() override;

  // Panner
  void pan(double azimuth,
           double elevation,
           const AudioBus* inputBus,
           AudioBus* outputBus,
           size_t framesToProcess,
           AudioBus::ChannelInterpretation) override;
  void panWithSampleAccurateValues(double* azimuth,
                                   double* elevation,
                                   const AudioBus* inputBus,
                                   AudioBus* outputBus,
                                   size_t framesToProcess,
                                   AudioBus::ChannelInterpretation) override;

  void reset() override;

  size_t fftSize() const { return fftSizeForSampleRate(m_sampleRate); }
  static size_t fftSizeForSampleRate(float sampleRate);

  float sampleRate() const { return m_sampleRate; }

  double tailTime() const override;
  double latencyTime() const override;

 private:
  // Given an azimuth angle in the range -180 -> +180, returns the corresponding
  // azimuth index for the database, and azimuthBlend which is an interpolation
  // value from 0 -> 1.
  int calculateDesiredAzimuthIndexAndBlend(double azimuth,
                                           double& azimuthBlend);

  RefPtr<HRTFDatabaseLoader> m_databaseLoader;

  float m_sampleRate;

  // We maintain two sets of convolvers for smooth cross-faded interpolations
  // when then azimuth and elevation are dynamically changing.  When the
  // azimuth and elevation are not changing, we simply process with one
  // of the two sets.  Initially we use CrossfadeSelection1 corresponding to
  // m_convolverL1 and m_convolverR1.  Whenever the azimuth or elevation
  // changes, a crossfade is initiated to transition to the new position. So if
  // we're currently processing with CrossfadeSelection1, then we transition to
  // CrossfadeSelection2 (and vice versa).  If we're in the middle of a
  // transition, then we wait until it is complete before initiating a new
  // transition.

  // Selects either the convolver set (m_convolverL1, m_convolverR1) or
  // (m_convolverL2, m_convolverR2).
  enum CrossfadeSelection { CrossfadeSelection1, CrossfadeSelection2 };

  CrossfadeSelection m_crossfadeSelection;

  // azimuth/elevation for CrossfadeSelection1.
  int m_azimuthIndex1;
  double m_elevation1;

  // azimuth/elevation for CrossfadeSelection2.
  int m_azimuthIndex2;
  double m_elevation2;

  // A crossfade value 0 <= m_crossfadeX <= 1.
  float m_crossfadeX;

  // Per-sample-frame crossfade value increment.
  float m_crossfadeIncr;

  FFTConvolver m_convolverL1;
  FFTConvolver m_convolverR1;
  FFTConvolver m_convolverL2;
  FFTConvolver m_convolverR2;

  AudioDelayDSPKernel m_delayLineL;
  AudioDelayDSPKernel m_delayLineR;

  AudioFloatArray m_tempL1;
  AudioFloatArray m_tempR1;
  AudioFloatArray m_tempL2;
  AudioFloatArray m_tempR2;
};

}  // namespace blink

#endif  // HRTFPanner_h