xbmc/utils/PCMAmplifier.cpp

   1 /*
   2  *      Copyright (C) 2005-2008 Team XBMC
   3  *      http://www.xbmc.org
   4  *
   5  *  This Program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; either version 2, or (at your option)
   8  *  any later version.
   9  *
  10  *  This Program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with XBMC; see the file COPYING.  If not, write to
  17  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  18  *  http://www.gnu.org/copyleft/gpl.html
  19  *
  20  */
  21
  22 #include "PCMAmplifier.h"
  23
  24 #include <math.h>
  25
  26 CPCMAmplifier::CPCMAmplifier() : m_nVolume(VOLUME_MAXIMUM), m_dFactor(0)
  27 {
  28 }
  29
  30 CPCMAmplifier::~CPCMAmplifier()
  31 {
  32 }
  33
  34 void CPCMAmplifier::SetVolume(int nVolume)
  35 {
  36   m_nVolume = nVolume;
  37   if (nVolume > VOLUME_MAXIMUM)
  38     nVolume = VOLUME_MAXIMUM;
  39
  40   if (nVolume < VOLUME_MINIMUM)
  41     nVolume = VOLUME_MINIMUM;
  42
  43   if( nVolume == VOLUME_MINIMUM)
  44     m_dFactor = 0;
  45   else
  46     m_dFactor = pow(10,nVolume/2000.f);
  47 }
  48
  49 int  CPCMAmplifier::GetVolume()
  50 {
  51   return m_nVolume;
  52 }
  53
  54      // only works on 16bit samples
  55 void CPCMAmplifier::DeAmplify(short *pcm, int nSamples)
  56 {
  57   if (m_dFactor >= 1.0)
  58   {
  59     // no process required. using >= to make sure no amp is ever done (only de-amp)
  60     return;
  61   }
  62
  63   for (int nSample=0; nSample<nSamples; nSample++)
  64   {
  65     int nSampleValue = pcm[nSample]; // must be int. so that we can check over/under flow
  66     nSampleValue = (int)((double)nSampleValue * m_dFactor);
  67
  68     pcm[nSample] = (short)nSampleValue;
  69   }
  70 }