fm.cpp

/**********************************************************************
*          Copyright (c) 2014, Hogeschool voor de Kunsten Utrecht
*                      Hilversum, the Netherlands
*                          All rights reserved
***********************************************************************
*  This program is free software: you can redistribute it and/or modify
*  it under the terms of the GNU General Public License as published by
*  the Free Software Foundation, either version 3 of the License, or
*  (at your option) any later version.
*
*  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 General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with this program.
*  If not, see <http://www.gnu.org/licenses/>.
***********************************************************************
*
*  File name     : fm.cpp
*  System name   : audio_io / Portaudio
* 
*  Description   : frequency modulation
*		   Example for the audio_io C++ class for Portaudio
*
*  Author        : Marc Groenewegen
*  E-mail        : marcg@dinkum.nl
*
**********************************************************************/
#include <iostream>
#include "audio_io.h"

using namespace std;

#define SAMPLERATE		44100
#define NROFCHANNELS		2
#define NUM_SECONDS		3

#define FRAMESPERBUFFER		64


int main(int argc,char** argv)
{
Audio_IO audiostream;
float samplebuffer[FRAMESPERBUFFER * NROFCHANNELS];
unsigned long x=0;		// sample index
unsigned long bufptr=0;		// pointer into sample buffer
double freq[]={1500.0,850};	// base frequency of each channel
double amp[]={0.4,0.4};		// base amplitude of each channel
double mod_freq[]={20,5};	// modulation freq for each channel
double mod_depth[]={20*M_PI,10*M_PI}; // modulation depth for each channel
double xx;			// 2 PI/fs version of x
int output_device=0;

  audiostream.set_samplerate(SAMPLERATE);
  audiostream.set_nrofchannels(NROFCHANNELS);
  audiostream.set_framesperbuffer(FRAMESPERBUFFER);

  audiostream.initialise();
  audiostream.list_devices();
  cout << "Give output device number: ";
  cin >> output_device;
  audiostream.set_output_device(output_device);
  audiostream.start_server();

  do{
    // Fill a new buffer with samples
    for(bufptr=0; bufptr < FRAMESPERBUFFER*NROFCHANNELS; bufptr+=NROFCHANNELS)
    {

      /*
       * sine shaped frequency (phase) modulation
       */
      xx = x * 2.0*M_PI / SAMPLERATE;
      // loop over the channels in one frame
      for(int channel=0;channel<NROFCHANNELS;channel++){
        samplebuffer[bufptr+channel] =
          (float)(amp[channel] * sin(xx*freq[channel] + mod_depth[channel]*sin(xx * mod_freq[channel])));
      } // for channel
      x++; // advance to next (global) time index
      mod_freq[0] *= 0.99999; // just for fun
    } // for buffer index

    // send buffer to Portaudio
    audiostream.write(samplebuffer);
  } while(x < (SAMPLERATE * NUM_SECONDS) );

  audiostream.finalise();

  return 0;
} // main()