annotate src/Modules/NAP/ModuleHCL.cc @ 611:0fbaf443ec82

Carfac C++ revision 3, indluding more style improvements. The output structs are now classes again, and have separate storage methods for each output structure along with flags in the Run and RunSegment methods to allow for only storing NAPs if desired.

// Copyright 2007-2010, Thomas Walters
//
// AIM-C: A C++ implementation of the Auditory Image Model
// http://www.acousticscale.org/AIMC
//
// 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
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/*!
 * \file
 * \brief Halfwave rectification, compression and lowpass filtering.
 *
 * \author Thomas Walters <[e-mail]>
 * \date created 2007/03/07
 * \version \$Id$
 */

#include <cmath>

#include "Modules/NAP/ModuleHCL.h"

namespace aimc {
ModuleHCL::ModuleHCL(Parameters *parameters) : Module(parameters) {
  module_identifier_ = "hcl";
  module_type_ = "nap";
  module_description_ = "Halfwave rectification, compression "
                        "and lowpass filtering";
  module_version_ = "$Id$";

  do_lowpass_ = parameters_->DefaultBool("nap.do_lowpass", true);
  do_log_ = parameters_->DefaultBool("nap.do_log_compression", false);
  lowpass_cutoff_ = parameters_->DefaultFloat("nap.lowpass_cutoff", 1200.0);
  lowpass_order_ = parameters_->DefaultInt("nap.lowpass_order", 2);
}

ModuleHCL::~ModuleHCL() {
}

bool ModuleHCL::InitializeInternal(const SignalBank &input) {
  time_constant_ = 1.0f / (2.0f * M_PI * lowpass_cutoff_);
  channel_count_ = input.channel_count();
  output_.Initialize(input);
  ResetInternal();
  return true;
}

void ModuleHCL::ResetInternal() {
  xn_ = 0.0f;
  yn_ = 0.0f;
  yns_.clear();
  yns_.resize(channel_count_);
  for (int c = 0; c < channel_count_; ++c) {
    yns_[c].resize(lowpass_order_, 0.0f);
  }
}

/* With do_log, the signal is first scaled up so that values <1.0 become
 * negligible. This just rescales the sample values to fill the range of a
 * 16-bit signed integer, then we lose the bottom bit of resolution. If the
 * signal was sampled at 16-bit resolution, there shouldn't be anything to
 * speak of there anyway. If it was sampled using a higher resolution, then
 * some data will be discarded.
 */
void ModuleHCL::Process(const SignalBank &input) {
  output_.set_start_time(input.start_time());
  for (int c = 0; c < input.channel_count(); ++c) {
    for (int i = 0; i < input.buffer_length(); ++i) {
      if (input[c][i] < 0.0f) {
        output_.set_sample(c, i, 0.0f);
      } else {
        float s = input[c][i];
        if (do_log_) {
          s *= pow(2.0f, 15);
          if (s < 1.0f) s = 1.0f;
          s = 20.0f * log10(s);
        }
        output_.set_sample(c, i, s);
      }
    }
    if (do_lowpass_) {
      float b = exp(-1.0f / (input.sample_rate() * time_constant_));
      float gain = 1.0f / (1.0f - b);
      for (int j = 0; j < lowpass_order_; j++) {
        for (int k = 0; k < output_.buffer_length(); ++k) {
          xn_ = output_[c][k];
          yn_ = xn_ + b * yns_[c][j];
          yns_[c][j] = yn_;
          output_.set_sample(c, k, yn_ / gain);
        }
      }
    }
  }
  PushOutput();
}
}  // namespace aimc