src/Audio/ToneSynthesiser.hpp

   1 /*
   2 Copyright_License {
   3
   4   XCSoar Glide Computer - http://www.xcsoar.org/
   5   Copyright (C) 2000-2013 The XCSoar Project
   6   A detailed list of copyright holders can be found in the file "AUTHORS".
   7
   8   This program is free software; you can redistribute it and/or
   9   modify it under the terms of the GNU General Public License
  10   as published by the Free Software Foundation; either version 2
  11   of the License, or (at your option) any later version.
  12
  13   This program is distributed in the hope that it will be useful,
  14   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16   GNU General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with this program; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21 }
  22 */
  23
  24 #ifndef XCSOAR_AUDIO_TONE_SYNTHESISER_HPP
  25 #define XCSOAR_AUDIO_TONE_SYNTHESISER_HPP
  26
  27 #include "PCMSynthesiser.hpp"
  28 #include "Compiler.h"
  29
  30 /**
  31  * This class generates tones with a sine wave.
  32  */
  33 class ToneSynthesiser : public PCMSynthesiser {
  34   unsigned volume, angle, increment;
  35
  36 public:
  37   constexpr
  38   ToneSynthesiser():volume(100), angle(0), increment(0) {}
  39
  40   /**
  41    * Set the (software) volume of the generated tone.
  42    *
  43    * @param _volume the new volume level, 0 indicating muted, 100
  44    * means full volume
  45    */
  46   void SetVolume(unsigned _volume) {
  47     volume = _volume;
  48   }
  49
  50   void SetTone(unsigned sample_rate, unsigned tone_hz);
  51
  52   /* methods from class PCMSynthesiser */
  53   virtual void Synthesise(int16_t *buffer, size_t n);
  54
  55 protected:
  56   /**
  57    * Returns the number of samples until the sample value gets close
  58    * to zero.
  59    */
  60   gcc_pure
  61   unsigned ToZero() const;
  62
  63   /**
  64    * Start a new period.
  65    */
  66   void Restart() {
  67     angle = 0;
  68   }
  69 };
  70
  71 #endif