text: /*
   * 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.
   * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
   *     its contributors may be used to endorse or promote products derived
   *     from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE 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 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 OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_REVERB_CONVOLVER_H_
  #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_REVERB_CONVOLVER_H_
  
  #include <memory>
  
  #include "third_party/blink/renderer/platform/audio/audio_array.h"
  #include "third_party/blink/renderer/platform/audio/direct_convolver.h"
  #include "third_party/blink/renderer/platform/audio/fft_convolver.h"
  #include "third_party/blink/renderer/platform/audio/reverb_accumulation_buffer.h"
  #include "third_party/blink/renderer/platform/audio/reverb_convolver_stage.h"
  #include "third_party/blink/renderer/platform/audio/reverb_input_buffer.h"
  #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
  #include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
  #include "third_party/blink/renderer/platform/wtf/vector.h"
  
  namespace blink {
  
  class AudioChannel;
  
  class PLATFORM_EXPORT ReverbConvolver {
    USING_FAST_MALLOC(ReverbConvolver);
  
   public:
    // maxFFTSize can be adjusted (from say 2048 to 32768) depending on how much
    // precision is necessary.  For certain tweaky de-convolving applications the
    // phase errors add up quickly and lead to non-sensical results with larger
    // FFT sizes and single-precision floats.  In these cases 2048 is a good
    // size.  If not doing multi-threaded convolution, then should not go > 8192.
    ReverbConvolver(AudioChannel* impulse_response,
                    unsigned render_slice_size,
                    unsigned max_fft_size,
                    size_t convolver_render_phase,
                    bool use_background_threads,
                    float scale);
    ReverbConvolver(const ReverbConvolver&) = delete;
    ReverbConvolver& operator=(const ReverbConvolver&) = delete;
    ~ReverbConvolver();
  
    void Process(const AudioChannel* source_channel,
                 AudioChannel* destination_channel,
                 uint32_t frames_to_process);
    void Reset();
  
    ReverbInputBuffer* InputBuffer() { return &input_buffer_; }
  
    size_t LatencyFrames() const;
  
   private:
    void ProcessInBackground();
  
    Vector<std::unique_ptr<ReverbConvolverStage>> stages_;
    Vector<std::unique_ptr<ReverbConvolverStage>> background_stages_;
    size_t impulse_response_length_;
  
    ReverbAccumulationBuffer accumulation_buffer_;
  
    // One or more background threads read from this input buffer which is fed
    // from the realtime thread.
    ReverbInputBuffer input_buffer_;
  
    // First stage will be of size m_minFFTSize.  Each next stage will be twice as
    // big until we hit m_maxFFTSize.
    unsigned min_fft_size_;
    unsigned max_fft_size_;
  
    // But don't exceed this size in the real-time thread (if we're doing
    // background processing).
    unsigned max_realtime_fft_size_;
  
    // Background thread and synchronization
    std::unique_ptr<Thread> background_thread_;
  };
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_REVERB_CONVOLVER_H_
  