OnlineDeltaFeature Class Reference

#include <online-feature.h>

Inheritance diagram for OnlineDeltaFeature:

Collaboration diagram for OnlineDeltaFeature:

Public Member Functions
virtual int32	Dim () const
virtual bool	IsLastFrame (int32 frame) const
	Returns true if this is the last frame. More...
virtual BaseFloat	FrameShiftInSeconds () const
virtual int32	NumFramesReady () const
	returns the feature dimension. More...
virtual void	GetFrame (int32 frame, VectorBase< BaseFloat > *feat)
	Gets the feature vector for this frame. More...
	OnlineDeltaFeature (const DeltaFeaturesOptions &opts, OnlineFeatureInterface *src)
Public Member Functions inherited from OnlineFeatureInterface
virtual void	GetFrames (const std::vector< int32 > &frames, MatrixBase< BaseFloat > *feats)
	This is like GetFrame() but for a collection of frames. More...
virtual	~OnlineFeatureInterface ()
	Virtual destructor. More...

Private Attributes
OnlineFeatureInterface *	src_
DeltaFeaturesOptions	opts_
DeltaFeatures	delta_features_

Detailed Description

Definition at line 530 of file online-feature.h.

Constructor & Destructor Documentation

OnlineDeltaFeature()

OnlineDeltaFeature	(	const DeltaFeaturesOptions &	opts,
		OnlineFeatureInterface *	src
	)

Definition at line 600 of file online-feature.cc.

                                                                   :
    src_(src), opts_(opts), delta_features_(opts) { }

Member Function Documentation

Dim()

int32 Dim ( ) const

virtual

Implements OnlineFeatureInterface.

Definition at line 557 of file online-feature.cc.

References OnlineFeatureInterface::Dim(), and OnlineTransform::src_.

Referenced by OnlineCacheFeature::GetFrame(), OnlineAppendFeature::GetFrame(), and OnlineCacheFeature::GetFrames().

                                    {
  int32 src_dim = src_->Dim();
  return src_dim * (1 + opts_.order);
}

FrameShiftInSeconds()

virtual BaseFloat FrameShiftInSeconds ( ) const

inlinevirtual

Implements OnlineFeatureInterface.

Definition at line 540 of file online-feature.h.

                                                {
    return src_->FrameShiftInSeconds();
  }

GetFrame()

void GetFrame ( int32  frame, VectorBase< BaseFloat > *  feat  )

virtual

Gets the feature vector for this frame.

Before calling this for a given frame, it is assumed that you called NumFramesReady() and it returned a number greater than "frame". Otherwise this call will likely crash with an assert failure. This function is not declared const, in case there is some kind of caching going on, but most of the time it shouldn't modify the class.

Implements OnlineFeatureInterface.

Definition at line 573 of file online-feature.cc.

References OnlineFeatureInterface::Dim(), VectorBase< Real >::Dim(), OnlineTransform::Dim(), OnlineFeatureInterface::GetFrame(), KALDI_ASSERT, OnlineFeatureInterface::NumFramesReady(), OnlineTransform::NumFramesReady(), and OnlineTransform::src_.

                                                                   {
  KALDI_ASSERT(frame >= 0 && frame < NumFramesReady());
  KALDI_ASSERT(feat->Dim() == Dim());
  // We'll produce a temporary matrix containing the features we want to
  // compute deltas on, but truncated to the necessary context.
  int32 context = opts_.order * opts_.window;
  int32 left_frame = frame - context,
      right_frame = frame + context,
      src_frames_ready = src_->NumFramesReady();
  if (left_frame < 0) left_frame = 0;
  if (right_frame >= src_frames_ready)
    right_frame = src_frames_ready - 1;
  KALDI_ASSERT(right_frame >= left_frame);
  int32 temp_num_frames = right_frame + 1 - left_frame,
      src_dim = src_->Dim();
  Matrix<BaseFloat> temp_src(temp_num_frames, src_dim);
  for (int32 t = left_frame; t <= right_frame; t++) {
    SubVector<BaseFloat> temp_row(temp_src, t - left_frame);
    src_->GetFrame(t, &temp_row);
  }
  int32 temp_t = frame - left_frame;  // temp_t is the offset of frame "frame"
                                      // within temp_src
  delta_features_.Process(temp_src, temp_t, feat);
}

IsLastFrame()

virtual bool IsLastFrame ( int32  frame ) const

inlinevirtual

Returns true if this is the last frame.

Frame indices are zero-based, so the first frame is zero. IsLastFrame(-1) will return false, unless the file is empty (which is a case that I'm not sure all the code will handle, so be careful). This function may return false for some frame if we haven't yet decided to terminate decoding, but later true if we decide to terminate decoding. This function exists mainly to correctly handle end effects in feature extraction, and is not a mechanism to determine how many frames are in the decodable object (as it used to be, and for backward compatibility, still is, in the Decodable interface).

Implements OnlineFeatureInterface.

Definition at line 537 of file online-feature.h.

                                              {
    return src_->IsLastFrame(frame);
  }

NumFramesReady()

int32 NumFramesReady ( ) const

virtual

returns the feature dimension.

Returns the total number of frames, since the start of the utterance, that are now available. In an online-decoding context, this will likely increase with time as more data becomes available.

Implements OnlineFeatureInterface.

Definition at line 562 of file online-feature.cc.

References OnlineFeatureInterface::IsLastFrame(), OnlineFeatureInterface::NumFramesReady(), and OnlineTransform::src_.

                                               {
  int32 num_frames = src_->NumFramesReady(),
      context = opts_.order * opts_.window;
  // "context" is the number of frames on the left or (more relevant
  // here) right which we need in order to produce the output.
  if (num_frames > 0 && src_->IsLastFrame(num_frames-1))
    return num_frames;
  else
    return std::max<int32>(0, num_frames - context);
}

Member Data Documentation

delta_features_

DeltaFeatures delta_features_

private

Definition at line 557 of file online-feature.h.

opts_

DeltaFeaturesOptions opts_

private

Definition at line 556 of file online-feature.h.

src_

OnlineFeatureInterface* src_

private

Definition at line 555 of file online-feature.h.

Referenced by OnlineCacheFeature::GetFrame(), and OnlineCacheFeature::GetFrames().

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

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