feature-fbank.h

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// feat/feature-fbank.h

// Copyright 2009-2012  Karel Vesely
//                2016  Johns Hopkins University (author: Daniel Povey)

// See ../../COPYING for clarification regarding multiple authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABLITY OR NON-INFRINGEMENT.
// See the Apache 2 License for the specific language governing permissions and
// limitations under the License.

#ifndef KALDI_FEAT_FEATURE_FBANK_H_
#define KALDI_FEAT_FEATURE_FBANK_H_

#include <map>
#include <string>

#include "feat/feature-common.h"
#include "feat/feature-functions.h"
#include "feat/feature-window.h"
#include "feat/mel-computations.h"

namespace kaldi {


struct FbankOptions {
  FrameExtractionOptions frame_opts;
  MelBanksOptions mel_opts;
  bool use_energy;  // append an extra dimension with energy to the filter banks
  BaseFloat energy_floor;
  bool raw_energy;  // If true, compute energy before preemphasis and windowing
  bool htk_compat;  // If true, put energy last (if using energy)
  bool use_log_fbank;  // if true (default), produce log-filterbank, else linear
  bool use_power;  // if true (default), use power in filterbank analysis, else magnitude.

  FbankOptions(): mel_opts(23),
                 // defaults the #mel-banks to 23 for the FBANK computations.
                 // this seems to be common for 16khz-sampled data,
                 // but for 8khz-sampled data, 15 may be better.
                 use_energy(false),
                 energy_floor(0.0),
                 raw_energy(true),
                 htk_compat(false),
                 use_log_fbank(true),
                 use_power(true) {}

  void Register(OptionsItf *opts) {
    frame_opts.Register(opts);
    mel_opts.Register(opts);
    opts->Register("use-energy", &use_energy,
                   "Add an extra dimension with energy to the FBANK output.");
    opts->Register("energy-floor", &energy_floor,
                   "Floor on energy (absolute, not relative) in FBANK computation. "
                   "Only makes a difference if --use-energy=true; only necessary if "
                   "--dither=0.0.  Suggested values: 0.1 or 1.0");
    opts->Register("raw-energy", &raw_energy,
                   "If true, compute energy before preemphasis and windowing");
    opts->Register("htk-compat", &htk_compat, "If true, put energy last.  "
                   "Warning: not sufficient to get HTK compatible features (need "
                   "to change other parameters).");
    opts->Register("use-log-fbank", &use_log_fbank,
                   "If true, produce log-filterbank, else produce linear.");
    opts->Register("use-power", &use_power,
                   "If true, use power, else use magnitude.");
  }
};


class FbankComputer {
 public:
  typedef FbankOptions Options;

  explicit FbankComputer(const FbankOptions &opts);
  FbankComputer(const FbankComputer &other);

  int32 Dim() const {
    return opts_.mel_opts.num_bins + (opts_.use_energy ? 1 : 0);
  }

  bool NeedRawLogEnergy() const { return opts_.use_energy && opts_.raw_energy; }

  const FrameExtractionOptions &GetFrameOptions() const {
    return opts_.frame_opts;
  }

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

  ~FbankComputer();

 private:
  const MelBanks *GetMelBanks(BaseFloat vtln_warp);


  FbankOptions opts_;
  BaseFloat log_energy_floor_;
  std::map<BaseFloat, MelBanks*> mel_banks_;  // BaseFloat is VTLN coefficient.
  SplitRadixRealFft<BaseFloat> *srfft_;
  // Disallow assignment.
  FbankComputer &operator =(const FbankComputer &other);
};

typedef OfflineFeatureTpl<FbankComputer> Fbank;

}  // namespace kaldi


#endif  // KALDI_FEAT_FEATURE_FBANK_H_