Featxtra

The featxtra toolbox lists a set of front-end tools and Signal Processing functions for Kaldi.

The toolbox includes:

• feature extraction for speech signals
  • Gammatone Frequency Representation, Gammatone Frequency Cepstral Coefficients
  • Gabor Features
  • DCT features (apply on ltsv, voicing stream)
• Voice Activity Detection
• additional signal filter operations

List of Functions

featbin

• featbin/compute-gtf-feats
  • extract Gammatone Frequency Representation (GTF)
  • extract Gammatone Frequency Cepstral Coefficients (GFCC)
• featbin/compute-gabor-feats
  • extract Gabor Features (GBF)
• featbin/compute-dct-feats
  • extract DCT Features from time domain signal
• featbin/apply-arma
  • apply Auto-Regressive Moving Average (ARMA) filtering on a spectral representation (e.g GTF )
• featbin/apply-ltsv
  • apply Long-Term Spectral Variabilityi (LTSV) stream on spectral representation (e.g GTF )
• featbin/apply-vad
  • apply Voice Activity Detection (VAD) using voicing and LTSV probability
• featbin/extract-dims
  • extract specified dimension range out of a feature matrix

feat

• feat/feature-gtf
  • GTF and GFCC feature implementation code

transform

• transform/featxtra-functions
  • additional signal processing functions

---

Instructions to run

1. Modify the Makefile in directories feat, featbin, and transform as follow:

• feat/Makefile should include feature-dctf.o feature-gtf.o feature-gabor.o under OBJFILES variable.
• featbin/Makefile should include compute-dctf-feats compute-gtf-feats compute-gabor-feats apply-arma apply-ltsv apply-nccf-to-pov apply-vad-merged apply-vad extract-dims under the BINFILES variable.
• transform/Makefile should include featxtra-functions.o under the OBJFILES variable.

2. Add the following code in the src/feat/feature-window.cc file

void ExtractWaveformRemainder(const VectorBase<BaseFloat> &wave,
                              const FrameExtractionOptions &opts,
                              Vector<BaseFloat> *wave_remainder) {
  int32 frame_shift = opts.WindowShift();
  int32 num_frames = NumFrames(wave.Dim(), opts);
  // offset is the amount at the start that has been extracted.
  int32 offset = num_frames * frame_shift;
  KALDI_ASSERT(wave_remainder != NULL);
  int32 remaining_len = wave.Dim() - offset;
  wave_remainder->Resize(remaining_len);
  KALDI_ASSERT(remaining_len >= 0);
  if (remaining_len > 0)
    wave_remainder->CopyFromVec(SubVector<BaseFloat>(wave, offset, remaining_len));
}

3. Add the following code in the src/featbin/feature-window.h file

// ExtractWaveformRemainder is useful if the waveform is coming in segments.
// It extracts the bit of the waveform at the end of this block that you
// would have to append the next bit of waveform to, if you wanted to have
// the same effect as everything being in one big block.
void ExtractWaveformRemainder(const VectorBase<BaseFloat> &wave,
                              const FrameExtractionOptions &opts,
                              Vector<BaseFloat> *wave_remainder);

Steps 2 and 3 are done because of this commit in the kaldi-asr project.

After these steps just run the make command again in the src directory to finally integrate these in your kaldi project.