chromium/src/third_party/blink/renderer/platform/audio/fft_frame.h

/*
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 *     from this software without specific prior written permission.
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#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_FFT_FRAME_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_FFT_FRAME_H_

#include <memory>

#include "build/build_config.h"
#include "third_party/blink/renderer/platform/audio/audio_array.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/forward.h"
#include "third_party/blink/renderer/platform/wtf/threading.h"

#if defined(WTF_USE_WEBAUDIO_FFMPEG)
struct RDFTContext;
#elif defined(WTF_USE_WEBAUDIO_PFFFT)
#include "third_party/blink/renderer/platform/wtf/hash_map.h"
#include "third_party/pffft/src/pffft.h"
#elif defined(OS_MAC)
#include <Accelerate/Accelerate.h>
#endif

namespace blink {

// Defines the interface for an "FFT frame", an object which is able to perform
// a forward and reverse FFT, internally storing the resultant frequency-domain
// data.

class PLATFORM_EXPORT FFTFrame {
  USING_FAST_MALLOC(FFTFrame);

 public:
  // The constructors, destructor, and methods up to the CROSS-PLATFORM section
  // have platform-dependent implementations.

  FFTFrame(unsigned fft_size);
  // creates a blank/empty frame for later use with createInterpolatedFrame()
  FFTFrame();
  FFTFrame(const FFTFrame& frame);
  ~FFTFrame();

  // Returns the smallest and largest supported FFT lengths.
  static int MinFFTSize();
  static int MaxFFTSize();

  // Perform any initialization needed.  Must be called from the main thread.
  static void Initialize(float sample_rate);
  static void Cleanup();

  // Compute the FFT of |data|, storing the resulting FFT in |real_data_| and
  // |imag_data_|.  |data| MUST have size at least |fft_size_| elements.
  void DoFFT(const float* data);

  // Compute the inverse FFT using the FFT data in |real_data_| and
  // |imag_data_|.  The inverse is saved in |data|.  |data| MUST have size at
  // least |fft_size_| elements.
  void DoInverseFFT(float* data);

  AudioFloatArray& RealData() { return real_data_; }
  const AudioFloatArray& RealData() const { return real_data_; }
  AudioFloatArray& ImagData() { return imag_data_; }
  const AudioFloatArray& ImagData() const { return imag_data_; }

  unsigned FftSize() const { return fft_size_; }
  unsigned Log2FFTSize() const { return log2fft_size_; }

  // CROSS-PLATFORM
  // The remaining public methods have cross-platform implementations:

  // Interpolates from frame1 -> frame2 as x goes from 0.0 -> 1.0
  static std::unique_ptr<FFTFrame> CreateInterpolatedFrame(
      const FFTFrame& frame1,
      const FFTFrame& frame2,
      double x);
  // zero-padding with dataSize <= fftSize
  void DoPaddedFFT(const float* data, size_t data_size);
  double ExtractAverageGroupDelay();
  void AddConstantGroupDelay(double sample_frame_delay);
  // multiplies ourself with frame : effectively operator*=()
  void Multiply(const FFTFrame&);
  // Scale the FFT data by the given scaling factor
  void ScaleFFT(float factor);

 private:
  void InterpolateFrequencyComponents(const FFTFrame& frame1,
                                      const FFTFrame& frame2,
                                      double x);

  unsigned fft_size_ = 0;

  // When using PFFFT, this slot is not irrelevant and not used because PFFFT
  // supports sizes that aren't a power of 2.
  // TODO(https://crbug.com/988121) Look into whether Mac vDSP really needs
  // this.
  unsigned log2fft_size_ = 0;

  // These two arrays contain the transformed data.  Instead of a single array
  // of complex numbers, we split the complex data into an array of the real
  // part and the imaginary part.
  //
  // Let the forward transform, X[k], of the real signal x[n] be defined by
  //
  //   X[k] = sum(x[n]*W^(k*n)) for n = 0 to N-1
  //
  // where W = exp(-2*pi*i/N), and N is the FFT size.
  //
  // Since x[n] is assumed to be real, X[k] has complex conjugate symmetry with
  // X[N-k] = conj(X[k]).  Thus, we only need to keep X[k] for k = 0 to N/2.
  // But since X[0] is purely real and X[N/2] is also purely real, so we could
  // place the real part of X[N/2] in the imaginary part of X[0].  Thus
  // for k = 1 to N/2:
  //
  //   real_data[k] = Re(X[k])
  //   imag_data[k] = Im(X[k])
  //
  // and
  //
  //   real_data[0] = Re(X[0]);
  //   imag_data[0] = Re(X[N/2])
  //
  // The routine |DoFFT| must produce transformed data in this format, and the
  // routine |DoInverseFFT| must expect transformed data in this format.
  AudioFloatArray real_data_;
  AudioFloatArray imag_data_;

#if defined(OS_MAC) && !defined(WTF_USE_WEBAUDIO_PFFFT)
  // Thin wrapper around FFTSetup so we can call the appropriate routines to
  // construct or release the FFTSetup objects.
  class FFTSetupDatum {
   public:
    FFTSetupDatum(unsigned fft_size);
    ~FFTSetupDatum();
    FFTSetup GetSetup() const { return setup_; }

   private:
    FFTSetup setup_;
  };

  // Returns the vector that holds all of the possible FFTSetupData
  // objects. This should be set up in the |Initialize()| method that is called
  // when the context is created.
  static Vector<std::unique_ptr<FFTSetupDatum>>& FFTSetups();

  static void InitializeFFTSetupForSize(wtf_size_t fft_order);

  DSPSplitComplex& DspSplitComplex() { return frame_; }
  DSPSplitComplex DspSplitComplex() const { return frame_; }
  static FFTSetup FftSetupForSize(unsigned fft_size);
  FFTSetup fft_setup_;
  DSPSplitComplex frame_;
#elif defined(WTF_USE_WEBAUDIO_FFMPEG)
  static RDFTContext* ContextForSize(unsigned fft_size, int trans);
  RDFTContext* forward_context_;
  RDFTContext* inverse_context_;
  float* GetUpToDateComplexData();
  AudioFloatArray complex_data_;
#elif defined(WTF_USE_WEBAUDIO_PFFFT)
  // Thin wrapper around PFFFT_Setup so we can call the appropriate PFFFT
  // routines to construct or release the PFFFT_Setup objects.
  class FFTSetup {
   public:
    FFTSetup(unsigned fft_size);
    ~FFTSetup();
    PFFFT_Setup* GetSetup() const { return setup_; }

   private:
    PFFFT_Setup* setup_;
  };

  // Returns the HashMap that holds all of the possible FFTSetup objects.  This
  // should be setup in the |Initialize()| method that is called when a context
  // is created.
  static HashMap<unsigned, std::unique_ptr<FFTSetup>>& FFTSetups();

  // Initialize an entry in FFTSetups for an FFT of order |fft_order|.  This can
  // be called from any thread, but if a new FFTSetup needs to be allocated,
  // then it MUST happen on the main thread.
  static void InitializeFFTSetupForSize(wtf_size_t fft_order);

  // Get the PFFFT_Setup that is appropriate for an FFT of order
  // |fft_order|. This can be called from any thread.
  // |InitializeFFTSetupForSize()| must be called for this size before calling
  // |FFTSetupForSize()|.
  static PFFFT_Setup* FFTSetupForSize(wtf_size_t fft_order);

  // Work array for converting PFFFT results to and from the format expected in
  // |real_data_| and |imag_datra_|.
  AudioFloatArray complex_data_;

  // Work array used by the PFFFT transform routines.  For real FFTs, this must
  // be the same size as the FFT size.
  AudioFloatArray pffft_work_;
#endif
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_FFT_FRAME_H_