third_party/WebKit/Source/platform/audio/FFTConvolver.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.
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 *     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
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#ifndef FFTConvolver_h
#define FFTConvolver_h

#include "platform/audio/AudioArray.h"
#include "platform/audio/FFTFrame.h"
#include "platform/wtf/Allocator.h"
#include "platform/wtf/Noncopyable.h"

namespace blink {

class PLATFORM_EXPORT FFTConvolver {
  USING_FAST_MALLOC(FFTConvolver);
  WTF_MAKE_NONCOPYABLE(FFTConvolver);

 public:
  // fftSize must be a power of two
  FFTConvolver(size_t fft_size);

  // For now, with multiple calls to Process(), framesToProcess MUST add up
  // EXACTLY to fftSize / 2
  //
  // FIXME: Later, we can do more sophisticated buffering to relax this
  // requirement...
  //
  // The input to output latency is equal to fftSize / 2
  //
  // Processing in-place is allowed...
  void Process(FFTFrame* fft_kernel,
               const float* source_p,
               float* dest_p,
               size_t frames_to_process);

  void Reset();

  size_t FftSize() const { return frame_.FftSize(); }

 private:
  FFTFrame frame_;

  // Buffer input until we get fftSize / 2 samples then do an FFT
  size_t read_write_index_;
  AudioFloatArray input_buffer_;

  // Stores output which we read a little at a time
  AudioFloatArray output_buffer_;

  // Saves the 2nd half of the FFT buffer, so we can do an overlap-add with the
  // 1st half of the next one
  AudioFloatArray last_overlap_buffer_;
};

}  // namespace blink

#endif  // FFTConvolver_h