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Duplex Mode

Finally, it is easy to use RtAudio for simultaneous audio input/output, or duplex operation. In this example, we simply pass the input data back to the output.

#include "RtAudio.h"
#include <iostream>
#include <cstdlib>
#include <cstring>
// Pass-through function.
int inout( void *outputBuffer, void *inputBuffer, unsigned int nBufferFrames,
double streamTime, RtAudioStreamStatus status, void *data )
{
// Since the number of input and output channels is equal, we can do
// a simple buffer copy operation here.
if ( status ) std::cout << "Stream over/underflow detected." << std::endl;
unsigned int *bytes = (unsigned int *) data;
memcpy( outputBuffer, inputBuffer, *bytes );
return 0;
}
int main()
{
RtAudio adac;
if ( adac.getDeviceCount() < 1 ) {
std::cout << "\nNo audio devices found!\n";
exit( 0 );
}
// Set the same number of channels for both input and output.
unsigned int bufferBytes, bufferFrames = 512;
RtAudio::StreamParameters iParams, oParams;
iParams.deviceId = 0; // first available device
iParams.nChannels = 2;
oParams.deviceId = 0; // first available device
oParams.nChannels = 2;
try {
adac.openStream( &oParams, &iParams, RTAUDIO_SINT32, 44100, &bufferFrames, &inout, (void *)&bufferBytes );
}
catch ( RtAudioError& e ) {
e.printMessage();
exit( 0 );
}
bufferBytes = bufferFrames * 2 * 4;
try {
adac.startStream();
char input;
std::cout << "\nRunning ... press <enter> to quit.\n";
std::cin.get(input);
// Stop the stream.
adac.stopStream();
}
catch ( RtAudioError& e ) {
e.printMessage();
goto cleanup;
}
cleanup:
if ( adac.isStreamOpen() ) adac.closeStream();
return 0;
}
RtAudio.h
RtAudioStreamStatus
unsigned int RtAudioStreamStatus
RtAudio stream status (over- or underflow) flags.
Definition RtAudio.h:159
RtAudioError
Exception handling class for RtAudio.
Definition RtAudio.h:220
RtAudioError::printMessage
virtual void printMessage(void) const
Prints thrown error message to stderr.
Definition RtAudio.h:243
RtAudio
Realtime audio i/o C++ classes.
Definition RtAudio.h:280
RtAudio::openStream
void openStream(RtAudio::StreamParameters *outputParameters, RtAudio::StreamParameters *inputParameters, RtAudioFormat format, unsigned int sampleRate, unsigned int *bufferFrames, RtAudioCallback callback, void *userData=NULL, RtAudio::StreamOptions *options=NULL, RtAudioErrorCallback errorCallback=NULL)
A public function for opening a stream with the specified parameters.
RtAudio::getDeviceCount
unsigned int getDeviceCount(void)
A public function that queries for the number of audio devices available.
Definition RtAudio.h:857
RtAudio::StreamParameters::nChannels
unsigned int nChannels
Definition RtAudio.h:315
RtAudio::closeStream
void closeStream(void)
A function that closes a stream and frees any associated stream memory.
Definition RtAudio.h:861
RtAudio::isStreamOpen
bool isStreamOpen(void) const
Returns true if a stream is open and false if not.
Definition RtAudio.h:865
RtAudio::StreamParameters::deviceId
unsigned int deviceId
Definition RtAudio.h:314
RtAudio::startStream
void startStream(void)
A function that starts a stream.
Definition RtAudio.h:862
RtAudio::stopStream
void stopStream(void)
Stop a stream, allowing any samples remaining in the output queue to be played.
Definition RtAudio.h:863
RtAudio::StreamParameters
The structure for specifying input or output stream parameters.
Definition RtAudio.h:313

In this example, audio recorded by the stream input will be played out during the next round of audio processing.

Note that a duplex stream can make use of two different devices (except when using the Linux Jack and Windows ASIO APIs). However, this may cause timing problems due to possible device clock variations, unless a common external "sync" is provided.

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