Recording

Using RtAudio for audio input is almost identical to the way it is used for playback. Here's the blocking playback example rewritten for recording:

#include "RtAudio.h"
#include <iostream>
#include <cstdlib>
#include <cstring>

int record( void *outputBuffer, void *inputBuffer, unsigned int nBufferFrames,
         double streamTime, RtAudioStreamStatus status, void *userData )
{
  if ( status )
    std::cout << "Stream overflow detected!" << std::endl;

  // Do something with the data in the "inputBuffer" buffer.

  return 0;
}

int main()
{
  RtAudio adc;
  std::vector<unsigned int> deviceIds = adc.getDeviceIds();
  if ( deviceIds.size() < 1 ) {
    std::cout << "\nNo audio devices found!\n";
    exit( 0 );
  }

  RtAudio::StreamParameters parameters;
  parameters.deviceId = adc.getDefaultInputDevice();
  parameters.nChannels = 2;
  parameters.firstChannel = 0;
  unsigned int sampleRate = 44100;
  unsigned int bufferFrames = 256; // 256 sample frames

  if ( adc.openStream( NULL, &parameters, RTAUDIO_SINT16,
                       sampleRate, &bufferFrames, &record ) ) {
    std::cout << '\n' << adc.getErrorText() << '\n' << std::endl;
    exit( 0 ); // problem with device settings
  }

  // Stream is open ... now start it.
  if ( adc.startStream() ) {
    std::cout << adc.getErrorText() << std::endl;
    goto cleanup;
  }
  
  char input;
  std::cout << "\nRecording ... press <enter> to quit.\n";
  std::cin.get( input );

  // Block released ... stop the stream
  if ( adc.isStreamRunning() )
    adc.stopStream();  // or could call adc.abortStream();

 cleanup:
  if ( adc.isStreamOpen() ) adc.closeStream();

  return 0;
}

In this example, we pass the address of the stream parameter structure as the second argument of the RtAudio::openStream() function and pass a NULL value for the output stream parameters. In this example, the record() callback function performs no specific operations.