SpectrogramComputer Class Reference

Class for computing spectrogram features. More...

#include <feature-spectrogram.h>

Collaboration diagram for SpectrogramComputer:

Public Types
typedef SpectrogramOptions	Options

Public Member Functions
	SpectrogramComputer (const SpectrogramOptions &opts)
	SpectrogramComputer (const SpectrogramComputer &other)
const FrameExtractionOptions &	GetFrameOptions () const
int32	Dim () const
bool	NeedRawLogEnergy () const
void	Compute (BaseFloat signal_raw_log_energy, BaseFloat vtln_warp, VectorBase< BaseFloat > *signal_frame, VectorBase< BaseFloat > *feature)
	Function that computes one frame of spectrogram features from one frame of signal. More...
	~SpectrogramComputer ()

Private Member Functions
SpectrogramComputer &	operator= (const SpectrogramComputer &other)

Private Attributes
SpectrogramOptions	opts_
BaseFloat	log_energy_floor_
SplitRadixRealFft< BaseFloat > *	srfft_

Detailed Description

Class for computing spectrogram features.

Definition at line 67 of file feature-spectrogram.h.

Member Typedef Documentation

Options

typedef SpectrogramOptions Options

Definition at line 69 of file feature-spectrogram.h.

Constructor & Destructor Documentation

SpectrogramComputer() [1/2]

SpectrogramComputer ( const SpectrogramOptions &  opts )

explicit

Definition at line 27 of file feature-spectrogram.cc.

References SpectrogramOptions::energy_floor, SpectrogramOptions::frame_opts, kaldi::Log(), SpectrogramComputer::log_energy_floor_, FrameExtractionOptions::PaddedWindowSize(), and SpectrogramComputer::srfft_.

    : opts_(opts), srfft_(NULL) {
  if (opts.energy_floor > 0.0)
    log_energy_floor_ = Log(opts.energy_floor);

  int32 padded_window_size = opts.frame_opts.PaddedWindowSize();
  if ((padded_window_size & (padded_window_size-1)) == 0)  // Is a power of two
    srfft_ = new SplitRadixRealFft<BaseFloat>(padded_window_size);
}

SpectrogramComputer() [2/2]

SpectrogramComputer

(

const SpectrogramComputer &

other

)

Definition at line 37 of file feature-spectrogram.cc.

References SpectrogramComputer::srfft_.

                                                                        :
    opts_(other.opts_), log_energy_floor_(other.log_energy_floor_), srfft_(NULL) {
  if (other.srfft_ != NULL)
    srfft_ = new SplitRadixRealFft<BaseFloat>(*other.srfft_);
}

~SpectrogramComputer()

~SpectrogramComputer

(

)

Definition at line 43 of file feature-spectrogram.cc.

References SpectrogramComputer::srfft_.

                                          {
  delete srfft_;
}

Member Function Documentation

Compute()

void Compute	(	BaseFloat	signal_raw_log_energy,
		BaseFloat	vtln_warp,
		VectorBase< BaseFloat > *	signal_frame,
		VectorBase< BaseFloat > *	feature
	)

Function that computes one frame of spectrogram features from one frame of signal.

Parameters

[in]	signal_raw_log_energy	The log-energy of the frame of the signal prior to windowing and pre-emphasis, or log(numeric_limits<float>::min()), whichever is greater. Must be ignored by this function if this class returns false from this->NeedsRawLogEnergy().
[in]	vtln_warp	This is ignored by this function, it's only needed for interface compatibility.
[in]	signal_frame	One frame of the signal, as extracted using the function ExtractWindow() using the options returned by this->GetFrameOptions(). The function will use the vector as a workspace, which is why it's a non-const pointer.
[out]	feature	Pointer to a vector of size this->Dim(), to which the computed feature will be written.

Definition at line 47 of file feature-spectrogram.cc.

References VectorBase< Real >::ApplyFloor(), kaldi::ComputePowerSpectrum(), VectorBase< Real >::CopyFromVec(), VectorBase< Real >::Data(), VectorBase< Real >::Dim(), SpectrogramComputer::Dim(), SpectrogramOptions::energy_floor, SpectrogramOptions::frame_opts, KALDI_ASSERT, kaldi::Log(), SpectrogramComputer::log_energy_floor_, SpectrogramComputer::opts_, FrameExtractionOptions::PaddedWindowSize(), SpectrogramOptions::raw_energy, kaldi::RealFft(), SpectrogramOptions::return_raw_fft, SpectrogramComputer::srfft_, and kaldi::VecVec().

                                                                  {
  KALDI_ASSERT(signal_frame->Dim() == opts_.frame_opts.PaddedWindowSize() &&
               feature->Dim() == this->Dim());


  // Compute energy after window function (not the raw one)
  if (!opts_.raw_energy)
    signal_raw_log_energy = Log(std::max<BaseFloat>(VecVec(*signal_frame, *signal_frame),
                                     std::numeric_limits<float>::epsilon()));

  if (srfft_ != NULL)  // Compute FFT using split-radix algorithm.
    srfft_->Compute(signal_frame->Data(), true);
  else  // An alternative algorithm that works for non-powers-of-two
    RealFft(signal_frame, true);

  if (opts_.return_raw_fft) {
    feature->CopyFromVec(*signal_frame);
    return;
  }

  // Convert the FFT into a power spectrum.
  ComputePowerSpectrum(signal_frame);
  SubVector<BaseFloat> power_spectrum(*signal_frame,
                                      0, signal_frame->Dim() / 2 + 1);

  power_spectrum.ApplyFloor(std::numeric_limits<float>::epsilon());
  power_spectrum.ApplyLog();

  feature->CopyFromVec(power_spectrum);

  if (opts_.energy_floor > 0.0 && signal_raw_log_energy < log_energy_floor_)
    signal_raw_log_energy = log_energy_floor_;
  // The zeroth spectrogram component is always set to the signal energy,
  // instead of the square of the constant component of the signal.
  (*feature)(0) = signal_raw_log_energy;
}

Dim()

int32 Dim ( ) const

inline

Definition at line 77 of file feature-spectrogram.h.

Referenced by SpectrogramComputer::Compute().

                    {
    if (opts_.return_raw_fft) {
      return opts_.frame_opts.PaddedWindowSize();
    } else {
      return opts_.frame_opts.PaddedWindowSize() / 2 + 1;
    }
  }

GetFrameOptions()

const FrameExtractionOptions& GetFrameOptions ( ) const

inline

Definition at line 73 of file feature-spectrogram.h.

                                                        {
    return opts_.frame_opts;
  }

NeedRawLogEnergy()

bool NeedRawLogEnergy ( ) const

inline

Definition at line 85 of file feature-spectrogram.h.

{ return opts_.raw_energy; }

operator=()

SpectrogramComputer& operator= ( const SpectrogramComputer &  other )

private

Member Data Documentation

log_energy_floor_

BaseFloat log_energy_floor_

private

Definition at line 115 of file feature-spectrogram.h.

Referenced by SpectrogramComputer::Compute(), and SpectrogramComputer::SpectrogramComputer().

opts_

SpectrogramOptions opts_

private

Definition at line 114 of file feature-spectrogram.h.

Referenced by SpectrogramComputer::Compute().

srfft_

SplitRadixRealFft<BaseFloat>* srfft_

private

Definition at line 116 of file feature-spectrogram.h.

Referenced by SpectrogramComputer::Compute(), SpectrogramComputer::SpectrogramComputer(), and SpectrogramComputer::~SpectrogramComputer().

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The documentation for this class was generated from the following files:

• feat/feature-spectrogram.h
• feat/feature-spectrogram.cc