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RtAudio.h File Reference

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class  RtAudio
 Realtime audio i/o C++ classes. More...
struct  RtAudio::DeviceInfo
 The public device information structure for returning queried values. More...
struct  RtAudio::StreamParameters
 The structure for specifying input or output stream parameters. More...
struct  RtAudio::StreamOptions
 The structure for specifying stream options. More...


typedef unsigned long RtAudioFormat
 RtAudio data format type.
typedef unsigned int RtAudioStreamFlags
 RtAudio stream option flags.
typedef unsigned int RtAudioStreamStatus
 RtAudio stream status (over- or underflow) flags.
typedef int(* RtAudioCallback) (void *outputBuffer, void *inputBuffer, unsigned int nFrames, double streamTime, RtAudioStreamStatus status, void *userData)
 RtAudio callback function prototype.
typedef std::function< void(RtAudioErrorType type, const std::string &errorText)> RtAudioErrorCallback
 RtAudio error callback function prototype.


enum  RtAudioErrorType {

Typedef Documentation

◆ RtAudioFormat

typedef unsigned long RtAudioFormat

RtAudio data format type.

Support for signed integers and floats. Audio data fed to/from an RtAudio stream is assumed to ALWAYS be in host byte order. The internal routines will automatically take care of any necessary byte-swapping between the host format and the soundcard. Thus, endian-ness is not a concern in the following format definitions. Note that there are no range checks for floating-point values that extend beyond plus/minus 1.0.

  • RTAUDIO_SINT8: 8-bit signed integer.
  • RTAUDIO_SINT16: 16-bit signed integer.
  • RTAUDIO_SINT24: 24-bit signed integer.
  • RTAUDIO_SINT32: 32-bit signed integer.
  • RTAUDIO_FLOAT32: Normalized between plus/minus 1.0.
  • RTAUDIO_FLOAT64: Normalized between plus/minus 1.0.

◆ RtAudioStreamFlags

typedef unsigned long RtAudioStreamFlags

RtAudio stream option flags.

The following flags can be OR'ed together to allow a client to make changes to the default stream behavior:

  • RTAUDIO_NONINTERLEAVED: Use non-interleaved buffers (default = interleaved).
  • RTAUDIO_MINIMIZE_LATENCY: Attempt to set stream parameters for lowest possible latency.
  • RTAUDIO_HOG_DEVICE: Attempt grab device for exclusive use.
  • RTAUDIO_ALSA_USE_DEFAULT: Use the "default" PCM device (ALSA only).
  • RTAUDIO_JACK_DONT_CONNECT: Do not automatically connect ports (JACK only).

By default, RtAudio streams pass and receive audio data from the client in an interleaved format. By passing the RTAUDIO_NONINTERLEAVED flag to the openStream() function, audio data will instead be presented in non-interleaved buffers. In this case, each buffer argument in the RtAudioCallback function will point to a single array of data, with nFrames samples for each channel concatenated back-to-back. For example, the first sample of data for the second channel would be located at index nFrames (assuming the buffer pointer was recast to the correct data type for the stream).

Certain audio APIs offer a number of parameters that influence the I/O latency of a stream. By default, RtAudio will attempt to set these parameters internally for robust (glitch-free) performance (though some APIs, like Windows DirectSound, make this difficult). By passing the RTAUDIO_MINIMIZE_LATENCY flag to the openStream() function, internal stream settings will be influenced in an attempt to minimize stream latency, though possibly at the expense of stream performance.

If the RTAUDIO_HOG_DEVICE flag is set, RtAudio will attempt to open the input and/or output stream device(s) for exclusive use. Note that this is not possible with all supported audio APIs.

If the RTAUDIO_SCHEDULE_REALTIME flag is set, RtAudio will attempt to select realtime scheduling (round-robin) for the callback thread.

If the RTAUDIO_ALSA_USE_DEFAULT flag is set, RtAudio will attempt to open the "default" PCM device when using the ALSA API. Note that this will override any specified input or output device id.

If the RTAUDIO_JACK_DONT_CONNECT flag is set, RtAudio will not attempt to automatically connect the ports of the client to the audio device.

◆ RtAudioStreamStatus

typedef unsigned long RtAudioStreamStatus

RtAudio stream status (over- or underflow) flags.

Notification of a stream over- or underflow is indicated by a non-zero stream status argument in the RtAudioCallback function. The stream status can be one of the following two options, depending on whether the stream is open for output and/or input:

  • RTAUDIO_INPUT_OVERFLOW: Input data was discarded because of an overflow condition at the driver.
  • RTAUDIO_OUTPUT_UNDERFLOW: The output buffer ran low, likely producing a break in the output sound.

◆ RtAudioCallback

typedef int(* RtAudioCallback) (void *outputBuffer, void *inputBuffer, unsigned int nFrames, double streamTime, RtAudioStreamStatus status, void *userData)

RtAudio callback function prototype.

All RtAudio clients must create a function of type RtAudioCallback to read and/or write data from/to the audio stream. When the underlying audio system is ready for new input or output data, this function will be invoked.

outputBufferFor output (or duplex) streams, the client should write nFrames of audio sample frames into this buffer. This argument should be recast to the datatype specified when the stream was opened. For input-only streams, this argument will be NULL.
inputBufferFor input (or duplex) streams, this buffer will hold nFrames of input audio sample frames. This argument should be recast to the datatype specified when the stream was opened. For output-only streams, this argument will be NULL.
nFramesThe number of sample frames of input or output data in the buffers. The actual buffer size in bytes is dependent on the data type and number of channels in use.
streamTimeThe number of seconds that have elapsed since the stream was started.
statusIf non-zero, this argument indicates a data overflow or underflow condition for the stream. The particular condition can be determined by comparison with the RtAudioStreamStatus flags.
userDataA pointer to optional data provided by the client when opening the stream (default = NULL).
To continue normal stream operation, the RtAudioCallback function should return a value of zero. To stop the stream and drain the output buffer, the function should return a value of one. To abort the stream immediately, the client should return a value of two.

◆ RtAudioErrorCallback

typedef std::function<void(RtAudioErrorType type, const std::string &errorText )> RtAudioErrorCallback

RtAudio error callback function prototype.

typeType of error.
errorTextError description.

Enumeration Type Documentation

◆ RtAudioErrorType


No error.


A non-critical error.


An unspecified error type.


No devices found on system.


An invalid device ID was specified.


A device in use was disconnected.


An error occurred during memory allocation.


An invalid parameter was specified to a function.


The function was called incorrectly.


A system driver error occurred.


A system error occurred.


A thread error occurred.

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