rtaudio

Class RtAudio

Description

Realtime audio i/o C++ classes.

RtAudio provides a common API (Application Programming Interface) for realtime audio input/output across Linux (native ALSA, Jack, and OSS), Macintosh OS X (CoreAudio and Jack), and Windows (DirectSound, ASIO and WASAPI) operating systems.

RtAudio WWW site: http://www.music.mcgill.ca/~gary/rtaudio/

RtAudio: realtime audio i/o C++ classes Copyright (c) 2001-2016 Gary P. Scavone

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

Any person wishing to distribute modifications to the Software is asked to send the modifications to the original developer so that they can be incorporated into the canonical version. This is, however, not a binding provision of this license.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Examples

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//

Nested Structures Summary

DeviceInfo The public device information structure for returning queried values.
StreamOptions The structure for specifying stream options.
StreamParameters The structure for specifying input or ouput stream parameters.

Methods Summary

getVersion A static function to determine the current RtAudio version.
getCompiledApi A static function to determine the available compiled audio APIs.
RtAudio The class constructor.
~RtAudio The destructor.
getCurrentApi Returns the audio API specifier for the current instance of RtAudio.
getDeviceCount A public function that queries for the number of audio devices available.
getDeviceInfo Return an RtAudio::DeviceInfo structure for a specified device number.
getDefaultOutputDevice A function that returns the index of the default output device.
getDefaultInputDevice A function that returns the index of the default input device.
openStream A public function for opening a stream with the specified parameters.
closeStream A function that closes a stream and frees any associated stream memory.
startStream A function that starts a stream.
stopStream Stop a stream, allowing any samples remaining in the output queue to be played.
abortStream Stop a stream, discarding any samples remaining in the input/output queue.
isStreamOpen Returns true if a stream is open and false if not.
isStreamRunning Returns true if the stream is running and false if it is stopped or not open.
getStreamTime Returns the number of elapsed seconds since the stream was started.
setStreamTime Set the stream time to a time in seconds greater than or equal to 0.
getStreamLatency Returns the internal stream latency in sample frames.
getStreamSampleRate Returns actual sample rate in use by the stream.
showWarnings Specify whether warning messages should be printed to stderr.
openRtApi

Source

From lines 261-574 in RtAudio.h

class RtAudio
{
 public:

  //! Audio API specifier arguments.
  enum Api {
    UNSPECIFIED,    /*!< Search for a working compiled API. */
    LINUX_ALSA,     /*!< The Advanced Linux Sound Architecture API. */
    LINUX_PULSE,    /*!< The Linux PulseAudio API. */
    LINUX_OSS,      /*!< The Linux Open Sound System API. */
    UNIX_JACK,      /*!< The Jack Low-Latency Audio Server API. */
    MACOSX_CORE,    /*!< Macintosh OS-X Core Audio API. */
    WINDOWS_WASAPI, /*!< The Microsoft WASAPI API. */
    WINDOWS_ASIO,   /*!< The Steinberg Audio Stream I/O API. */
    WINDOWS_DS,     /*!< The Microsoft Direct Sound API. */
    RTAUDIO_DUMMY   /*!< A compilable but non-functional API. */
  };

  //! The public device information structure for returning queried values.
  struct DeviceInfo {
    bool probed;                  /*!< true if the device capabilities were successfully probed. */
    std::string name;             /*!< Character string device identifier. */
    unsigned int outputChannels;  /*!< Maximum output channels supported by device. */
    unsigned int inputChannels;   /*!< Maximum input channels supported by device. */
    unsigned int duplexChannels;  /*!< Maximum simultaneous input/output channels supported by device. */
    bool isDefaultOutput;         /*!< true if this is the default output device. */
    bool isDefaultInput;          /*!< true if this is the default input device. */
    std::vector<unsigned int> sampleRates; /*!< Supported sample rates (queried from list of standard rates). */
    unsigned int preferredSampleRate; /*!< Preferred sample rate, eg. for WASAPI the system sample rate. */
    RtAudioFormat nativeFormats;  /*!< Bit mask of supported data formats. */

    // Default constructor.
    DeviceInfo()
      :probed(false), outputChannels(0), inputChannels(0), duplexChannels(0),
       isDefaultOutput(false), isDefaultInput(false), preferredSampleRate(0), nativeFormats(0) {}
  };

  //! The structure for specifying input or ouput stream parameters.
  struct StreamParameters {
    unsigned int deviceId;     /*!< Device index (0 to getDeviceCount() - 1). */
    unsigned int nChannels;    /*!< Number of channels. */
    unsigned int firstChannel; /*!< First channel index on device (default = 0). */

    // Default constructor.
    StreamParameters()
      : deviceId(0), nChannels(0), firstChannel(0) {}
  };

  //! The structure for specifying stream options.
  /*!
    The following flags can be OR'ed together to allow a client to
    make changes to the default stream behavior:

    - \e RTAUDIO_NONINTERLEAVED:    Use non-interleaved buffers (default = interleaved).
    - \e RTAUDIO_MINIMIZE_LATENCY:  Attempt to set stream parameters for lowest possible latency.
    - \e RTAUDIO_HOG_DEVICE:        Attempt grab device for exclusive use.
    - \e RTAUDIO_SCHEDULE_REALTIME: Attempt to select realtime scheduling for callback thread.
    - \e RTAUDIO_ALSA_USE_DEFAULT:  Use the "default" PCM device (ALSA 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 \c 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 \c
    nFrames (assuming the \c 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 Direct Sound, 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.
    The \c priority parameter will only be used if the RTAUDIO_SCHEDULE_REALTIME
    flag is set. It defines the thread's realtime priority.

    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.

    The \c numberOfBuffers parameter can be used to control stream
    latency in the Windows DirectSound, Linux OSS, and Linux Alsa APIs
    only.  A value of two is usually the smallest allowed.  Larger
    numbers can potentially result in more robust stream performance,
    though likely at the cost of stream latency.  The value set by the
    user is replaced during execution of the RtAudio::openStream()
    function by the value actually used by the system.

    The \c streamName parameter can be used to set the client name
    when using the Jack API.  By default, the client name is set to
    RtApiJack.  However, if you wish to create multiple instances of
    RtAudio with Jack, each instance must have a unique client name.
  */
  struct StreamOptions {
    RtAudioStreamFlags flags;      /*!< A bit-mask of stream flags (RTAUDIO_NONINTERLEAVED, RTAUDIO_MINIMIZE_LATENCY, RTAUDIO_HOG_DEVICE, RTAUDIO_ALSA_USE_DEFAULT). */
    unsigned int numberOfBuffers;  /*!< Number of stream buffers. */
    std::string streamName;        /*!< A stream name (currently used only in Jack). */
    int priority;                  /*!< Scheduling priority of callback thread (only used with flag RTAUDIO_SCHEDULE_REALTIME). */

    // Default constructor.
    StreamOptions()
    : flags(0), numberOfBuffers(0), priority(0) {}
  };

  //! A static function to determine the current RtAudio version.
  static std::string getVersion( void ) throw();

  //! A static function to determine the available compiled audio APIs.
  /*!
    The values returned in the std::vector can be compared against
    the enumerated list values.  Note that there can be more than one
    API compiled for certain operating systems.
  */
  static void getCompiledApi( std::vector<RtAudio::Api> &apis ) throw();

  //! The class constructor.
  /*!
    The constructor performs minor initialization tasks.  An exception
    can be thrown if no API support is compiled.

    If no API argument is specified and multiple API support has been
    compiled, the default order of use is JACK, ALSA, OSS (Linux
    systems) and ASIO, DS (Windows systems).
  */
  RtAudio( RtAudio::Api api=UNSPECIFIED );

  //! The destructor.
  /*!
    If a stream is running or open, it will be stopped and closed
    automatically.
  */
  ~RtAudio() throw();

  //! Returns the audio API specifier for the current instance of RtAudio.
  RtAudio::Api getCurrentApi( void ) throw();

  //! A public function that queries for the number of audio devices available.
  /*!
    This function performs a system query of available devices each time it
    is called, thus supporting devices connected \e after instantiation. If
    a system error occurs during processing, a warning will be issued. 
  */
  unsigned int getDeviceCount( void ) throw();

  //! Return an RtAudio::DeviceInfo structure for a specified device number.
  /*!

    Any device integer between 0 and getDeviceCount() - 1 is valid.
    If an invalid argument is provided, an RtAudioError (type = INVALID_USE)
    will be thrown.  If a device is busy or otherwise unavailable, the
    structure member "probed" will have a value of "false" and all
    other members are undefined.  If the specified device is the
    current default input or output device, the corresponding
    "isDefault" member will have a value of "true".
  */
  RtAudio::DeviceInfo getDeviceInfo( unsigned int device );

  //! A function that returns the index of the default output device.
  /*!
    If the underlying audio API does not provide a "default
    device", or if no devices are available, the return value will be
    0.  Note that this is a valid device identifier and it is the
    client's responsibility to verify that a device is available
    before attempting to open a stream.
  */
  unsigned int getDefaultOutputDevice( void ) throw();

  //! A function that returns the index of the default input device.
  /*!
    If the underlying audio API does not provide a "default
    device", or if no devices are available, the return value will be
    0.  Note that this is a valid device identifier and it is the
    client's responsibility to verify that a device is available
    before attempting to open a stream.
  */
  unsigned int getDefaultInputDevice( void ) throw();

  //! A public function for opening a stream with the specified parameters.
  /*!
    An RtAudioError (type = SYSTEM_ERROR) is thrown if a stream cannot be
    opened with the specified parameters or an error occurs during
    processing.  An RtAudioError (type = INVALID_USE) is thrown if any
    invalid device ID or channel number parameters are specified.

    \param outputParameters Specifies output stream parameters to use
           when opening a stream, including a device ID, number of channels,
           and starting channel number.  For input-only streams, this
           argument should be NULL.  The device ID is an index value between
           0 and getDeviceCount() - 1.
    \param inputParameters Specifies input stream parameters to use
           when opening a stream, including a device ID, number of channels,
           and starting channel number.  For output-only streams, this
           argument should be NULL.  The device ID is an index value between
           0 and getDeviceCount() - 1.
    \param format An RtAudioFormat specifying the desired sample data format.
    \param sampleRate The desired sample rate (sample frames per second).
    \param *bufferFrames A pointer to a value indicating the desired
           internal buffer size in sample frames.  The actual value
           used by the device is returned via the same pointer.  A
           value of zero can be specified, in which case the lowest
           allowable value is determined.
    \param callback A client-defined function that will be invoked
           when input data is available and/or output data is needed.
    \param userData An optional pointer to data that can be accessed
           from within the callback function.
    \param options An optional pointer to a structure containing various
           global stream options, including a list of OR'ed RtAudioStreamFlags
           and a suggested number of stream buffers that can be used to 
           control stream latency.  More buffers typically result in more
           robust performance, though at a cost of greater latency.  If a
           value of zero is specified, a system-specific median value is
           chosen.  If the RTAUDIO_MINIMIZE_LATENCY flag bit is set, the
           lowest allowable value is used.  The actual value used is
           returned via the structure argument.  The parameter is API dependent.
    \param errorCallback A client-defined function that will be invoked
           when an error has occured.
  */
  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 function that closes a stream and frees any associated stream memory.
  /*!
    If a stream is not open, this function issues a warning and
    returns (no exception is thrown).
  */
  void closeStream( void ) throw();

  //! A function that starts a stream.
  /*!
    An RtAudioError (type = SYSTEM_ERROR) is thrown if an error occurs
    during processing.  An RtAudioError (type = INVALID_USE) is thrown if a
    stream is not open.  A warning is issued if the stream is already
    running.
  */
  void startStream( void );

  //! Stop a stream, allowing any samples remaining in the output queue to be played.
  /*!
    An RtAudioError (type = SYSTEM_ERROR) is thrown if an error occurs
    during processing.  An RtAudioError (type = INVALID_USE) is thrown if a
    stream is not open.  A warning is issued if the stream is already
    stopped.
  */
  void stopStream( void );

  //! Stop a stream, discarding any samples remaining in the input/output queue.
  /*!
    An RtAudioError (type = SYSTEM_ERROR) is thrown if an error occurs
    during processing.  An RtAudioError (type = INVALID_USE) is thrown if a
    stream is not open.  A warning is issued if the stream is already
    stopped.
  */
  void abortStream( void );

  //! Returns true if a stream is open and false if not.
  bool isStreamOpen( void ) const throw();

  //! Returns true if the stream is running and false if it is stopped or not open.
  bool isStreamRunning( void ) const throw();

  //! Returns the number of elapsed seconds since the stream was started.
  /*!
    If a stream is not open, an RtAudioError (type = INVALID_USE) will be thrown.
  */
  double getStreamTime( void );

  //! Set the stream time to a time in seconds greater than or equal to 0.0.
  /*!
    If a stream is not open, an RtAudioError (type = INVALID_USE) will be thrown.
  */
  void setStreamTime( double time );

  //! Returns the internal stream latency in sample frames.
  /*!
    The stream latency refers to delay in audio input and/or output
    caused by internal buffering by the audio system and/or hardware.
    For duplex streams, the returned value will represent the sum of
    the input and output latencies.  If a stream is not open, an
    RtAudioError (type = INVALID_USE) will be thrown.  If the API does not
    report latency, the return value will be zero.
  */
  long getStreamLatency( void );

 //! Returns actual sample rate in use by the stream.
 /*!
   On some systems, the sample rate used may be slightly different
   than that specified in the stream parameters.  If a stream is not
   open, an RtAudioError (type = INVALID_USE) will be thrown.
 */
  unsigned int getStreamSampleRate( void );

  //! Specify whether warning messages should be printed to stderr.
  void showWarnings( bool value = true ) throw();

 protected:

  void openRtApi( RtAudio::Api api );
  RtApi *rtapi_;
};


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