content: /**
   * Copyright 2004-2006 DFKI GmbH.
   * All Rights Reserved.  Use is subject to license terms.
   * <p/>
   * This file is part of MARY TTS.
   * <p/>
   * MARY TTS is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as published by
   * the Free Software Foundation, version 3 of the License.
   * <p/>
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU Lesser General Public License for more details.
   * <p/>
   * You should have received a copy of the GNU Lesser General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  package marytts.signalproc.analysis;
  
  import marytts.signalproc.window.Window;
  import marytts.util.data.DoubleDataSource;
  import marytts.util.math.MathUtils;
  
  /**
   * @author Marc Schr&ouml;der
   *         <p/>
   *         Implements a frame based log spectrum analyser
   */
  public class ShortTermLogSpectrumAnalyser extends ShortTermSpectrumAnalyser {
  
      /**
       * Initialise a FrameBasedAnalyser.
       *
       * @param signal       the signal source to read from
       * @param fftSize      the size of the FFT to use
       * @param window       the window function to apply to each frame
       * @param frameShift   the number of samples by which to shift the window from
       *                     one frame analysis to the next; if this is smaller than window.getLength(),
       *                     frames will overlap.
       * @param samplingRate the number of samples in one second.
       * @throws IllegalArgumentException if the window is longer than fftSize, or
       *                                  fftSize is not a power of two.
       */
      public ShortTermLogSpectrumAnalyser(DoubleDataSource signal, int fftSize, Window window,
                                          int frameShift, int samplingRate) {
          super(signal, fftSize, window, frameShift, samplingRate);
      }
  
      /**
       * Apply this FrameBasedAnalyser to the given data.
       *
       * @param frame the data to analyse, which must be of the length prescribed by this
       *              FrameBasedAnalyser, i.e. by @see{#getFrameLengthSamples()}.
       * @return a double array of half the frame length
       * @throws IllegalArgumentException if frame does not have the prescribed length
       */
      @Override
      public double[] analyse(double[] frame) {
          double[] spectrum = super.analyse(frame);
  
          for (int i = 0; i < spectrum.length; i++) {
              spectrum[i] = MathUtils.db(spectrum[i]);
          }
          return spectrum;
      }
  
  }
  
  