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AudioDeviceManager Class Reference

Manages the state of some audio and midi i/o devices. More...

Inherits ChangeBroadcaster.

Classes

struct  AudioDeviceSetup
 This structure holds a set of properties describing the current audio setup. More...
 

Public Member Functions

 AudioDeviceManager ()
 Creates a default AudioDeviceManager.
 
 ~AudioDeviceManager ()
 Destructor.
 
String initialise (int numInputChannelsNeeded, int numOutputChannelsNeeded, const XmlElement *savedState, bool selectDefaultDeviceOnFailure, const String &preferredDefaultDeviceName=String(), const AudioDeviceSetup *preferredSetupOptions=nullptr)
 Opens a set of audio devices ready for use.
 
String initialiseWithDefaultDevices (int numInputChannelsNeeded, int numOutputChannelsNeeded)
 Resets everything to a default device setup, clearing any stored settings.
 
XmlElementcreateStateXml () const
 Returns some XML representing the current state of the manager.
 
void getAudioDeviceSetup (AudioDeviceSetup &setup)
 Returns the current device properties that are in use.
 
String setAudioDeviceSetup (const AudioDeviceSetup &newSetup, bool treatAsChosenDevice)
 Changes the current device or its settings.
 
AudioIODevicegetCurrentAudioDevice () const noexcept
 Returns the currently-active audio device.
 
String getCurrentAudioDeviceType () const
 Returns the type of audio device currently in use.
 
AudioIODeviceTypegetCurrentDeviceTypeObject () const
 Returns the currently active audio device type object.
 
void setCurrentAudioDeviceType (const String &type, bool treatAsChosenDevice)
 Changes the class of audio device being used.
 
void closeAudioDevice ()
 Closes the currently-open device.
 
void restartLastAudioDevice ()
 Tries to reload the last audio device that was running.
 
void addAudioCallback (AudioIODeviceCallback *newCallback)
 Registers an audio callback to be used.
 
void removeAudioCallback (AudioIODeviceCallback *callback)
 Deregisters a previously added callback.
 
double getCpuUsage () const
 Returns the average proportion of available CPU being spent inside the audio callbacks.
 
void setMidiInputEnabled (const String &midiInputDeviceName, bool enabled)
 Enables or disables a midi input device.
 
bool isMidiInputEnabled (const String &midiInputDeviceName) const
 Returns true if a given midi input device is being used.
 
void addMidiInputCallback (const String &midiInputDeviceName, MidiInputCallback *callback)
 Registers a listener for callbacks when midi events arrive from a midi input.
 
void removeMidiInputCallback (const String &midiInputDeviceName, MidiInputCallback *callback)
 Removes a listener that was previously registered with addMidiInputCallback().
 
void setDefaultMidiOutput (const String &deviceName)
 Sets a midi output device to use as the default.
 
String getDefaultMidiOutputName () const
 Returns the name of the default midi output.
 
MidiOutputgetDefaultMidiOutput () const noexcept
 Returns the current default midi output device.
 
const OwnedArray
< AudioIODeviceType > & 
getAvailableDeviceTypes ()
 Returns a list of the types of device supported.
 
virtual void createAudioDeviceTypes (OwnedArray< AudioIODeviceType > &types)
 Creates a list of available types.
 
void addAudioDeviceType (AudioIODeviceType *newDeviceType)
 Adds a new device type to the list of types.
 
void playTestSound ()
 Plays a beep through the current audio device.
 
void enableInputLevelMeasurement (bool enableMeasurement)
 Turns on level-measuring.
 
double getCurrentInputLevel () const
 Returns the current input level.
 
CriticalSectiongetAudioCallbackLock () noexcept
 Returns the a lock that can be used to synchronise access to the audio callback.
 
CriticalSectiongetMidiCallbackLock () noexcept
 Returns the a lock that can be used to synchronise access to the midi callback.
 
- Public Member Functions inherited from ChangeBroadcaster
 ChangeBroadcaster () noexcept
 Creates an ChangeBroadcaster.
 
virtual ~ChangeBroadcaster ()
 Destructor.
 
void addChangeListener (ChangeListener *listener)
 Registers a listener to receive change callbacks from this broadcaster.
 
void removeChangeListener (ChangeListener *listener)
 Unregisters a listener from the list.
 
void removeAllChangeListeners ()
 Removes all listeners from the list.
 
void sendChangeMessage ()
 Causes an asynchronous change message to be sent to all the registered listeners.
 
void sendSynchronousChangeMessage ()
 Sends a synchronous change message to all the registered listeners.
 
void dispatchPendingMessages ()
 If a change message has been sent but not yet dispatched, this will call sendSynchronousChangeMessage() to make the callback immediately.
 

Detailed Description

Manages the state of some audio and midi i/o devices.

This class keeps tracks of a currently-selected audio device, through with which it continuously streams data from an audio callback, as well as one or more midi inputs.

The idea is that your application will create one global instance of this object, and let it take care of creating and deleting specific types of audio devices internally. So when the device is changed, your callbacks will just keep running without having to worry about this.

The manager can save and reload all of its device settings as XML, which makes it very easy for you to save and reload the audio setup of your application.

And to make it easy to let the user change its settings, there's a component to do just that - the AudioDeviceSelectorComponent class, which contains a set of device selection/sample-rate/latency controls.

To use an AudioDeviceManager, create one, and use initialise() to set it up. Then call addAudioCallback() to register your audio callback with it, and use that to process your audio data.

The manager also acts as a handy hub for incoming midi messages, allowing a listener to register for messages from either a specific midi device, or from whatever the current default midi input device is. The listener then doesn't have to worry about re-registering with different midi devices if they are changed or deleted.

And yet another neat trick is that amount of CPU time being used is measured and available with the getCpuUsage() method.

The AudioDeviceManager is a ChangeBroadcaster, and will send a change message to listeners whenever one of its settings is changed.

See Also
AudioDeviceSelectorComponent, AudioIODevice, AudioIODeviceType

Constructor & Destructor Documentation

AudioDeviceManager::AudioDeviceManager ( )

Creates a default AudioDeviceManager.

Initially no audio device will be selected. You should call the initialise() method and register an audio callback with setAudioCallback() before it'll be able to actually make any noise.

AudioDeviceManager::~AudioDeviceManager ( )

Destructor.

Member Function Documentation

String AudioDeviceManager::initialise ( int  numInputChannelsNeeded,
int  numOutputChannelsNeeded,
const XmlElement savedState,
bool  selectDefaultDeviceOnFailure,
const String preferredDefaultDeviceName = String(),
const AudioDeviceSetup preferredSetupOptions = nullptr 
)

Opens a set of audio devices ready for use.

This will attempt to open either a default audio device, or one that was previously saved as XML.

Parameters
numInputChannelsNeededthe maximum number of input channels your app would like to use (the actual number of channels opened may be less than the number requested)
numOutputChannelsNeededthe maximum number of output channels your app would like to use (the actual number of channels opened may be less than the number requested)
savedStateeither a previously-saved state that was produced by createStateXml(), or nullptr if you want the manager to choose the best device to open.
selectDefaultDeviceOnFailureif true, then if the device specified in the XML fails to open, then a default device will be used instead. If false, then on failure, no device is opened.
preferredDefaultDeviceNameif this is not empty, and there's a device with this name, then that will be used as the default device (assuming that there wasn't one specified in the XML). The string can actually be a simple wildcard, containing "*" and "?" characters
preferredSetupOptionsif this is non-null, the structure will be used as the set of preferred settings when opening the device. If you use this parameter, the preferredDefaultDeviceName field will be ignored
Returns
an error message if anything went wrong, or an empty string if it worked ok.

Referenced by StandaloneFilterWindow::StandaloneFilterWindow().

String AudioDeviceManager::initialiseWithDefaultDevices ( int  numInputChannelsNeeded,
int  numOutputChannelsNeeded 
)

Resets everything to a default device setup, clearing any stored settings.

XmlElement* AudioDeviceManager::createStateXml ( ) const

Returns some XML representing the current state of the manager.

This stores the current device, its samplerate, block size, etc, and can be restored later with initialise().

Note that this can return a null pointer if no settings have been explicitly changed (i.e. if the device manager has just been left in its default state).

Referenced by StandaloneFilterWindow::~StandaloneFilterWindow().

void AudioDeviceManager::getAudioDeviceSetup ( AudioDeviceSetup setup)

Returns the current device properties that are in use.

See Also
setAudioDeviceSetup
String AudioDeviceManager::setAudioDeviceSetup ( const AudioDeviceSetup newSetup,
bool  treatAsChosenDevice 
)

Changes the current device or its settings.

If you want to change a device property, like the current sample rate or block size, you can call getAudioDeviceSetup() to retrieve the current settings, then tweak the appropriate fields in the AudioDeviceSetup structure, and pass it back into this method to apply the new settings.

Parameters
newSetupthe settings that you'd like to use
treatAsChosenDeviceif this is true and if the device opens correctly, these new settings will be taken as having been explicitly chosen by the user, and the next time createStateXml() is called, these settings will be returned. If it's false, then the device is treated as a temporary or default device, and a call to createStateXml() will return either the last settings that were made with treatAsChosenDevice as true, or the last XML settings that were passed into initialise().
Returns
an error message if anything went wrong, or an empty string if it worked ok.
See Also
getAudioDeviceSetup
AudioIODevice* AudioDeviceManager::getCurrentAudioDevice ( ) const
noexcept

Returns the currently-active audio device.

String AudioDeviceManager::getCurrentAudioDeviceType ( ) const

Returns the type of audio device currently in use.

See Also
setCurrentAudioDeviceType
AudioIODeviceType* AudioDeviceManager::getCurrentDeviceTypeObject ( ) const

Returns the currently active audio device type object.

Don't keep a copy of this pointer - it's owned by the device manager and could change at any time.

void AudioDeviceManager::setCurrentAudioDeviceType ( const String type,
bool  treatAsChosenDevice 
)

Changes the class of audio device being used.

This switches between, e.g. ASIO and DirectSound. On the Mac you probably won't ever call this because there's only one type: CoreAudio.

For a list of types, see getAvailableDeviceTypes().

void AudioDeviceManager::closeAudioDevice ( )

Closes the currently-open device.

You can call restartLastAudioDevice() later to reopen it in the same state that it was just in.

void AudioDeviceManager::restartLastAudioDevice ( )

Tries to reload the last audio device that was running.

Note that this only reloads the last device that was running before closeAudioDevice() was called - it doesn't reload any kind of saved-state, and can only be called after a device has been opened with SetAudioDevice().

If a device is already open, this call will do nothing.

void AudioDeviceManager::addAudioCallback ( AudioIODeviceCallback newCallback)

Registers an audio callback to be used.

The manager will redirect callbacks from whatever audio device is currently in use to all registered callback objects. If more than one callback is active, they will all be given the same input data, and their outputs will be summed.

If necessary, this method will invoke audioDeviceAboutToStart() on the callback object before returning.

To remove a callback, use removeAudioCallback().

Referenced by StandaloneFilterWindow::StandaloneFilterWindow().

void AudioDeviceManager::removeAudioCallback ( AudioIODeviceCallback callback)

Deregisters a previously added callback.

If necessary, this method will invoke audioDeviceStopped() on the callback object before returning.

See Also
addAudioCallback

Referenced by StandaloneFilterWindow::~StandaloneFilterWindow().

double AudioDeviceManager::getCpuUsage ( ) const

Returns the average proportion of available CPU being spent inside the audio callbacks.

Returns a value between 0 and 1.0

void AudioDeviceManager::setMidiInputEnabled ( const String midiInputDeviceName,
bool  enabled 
)

Enables or disables a midi input device.

The list of devices can be obtained with the MidiInput::getDevices() method.

Any incoming messages from enabled input devices will be forwarded on to all the listeners that have been registered with the addMidiInputCallback() method. They can either register for messages from a particular device, or from just the "default" midi input.

Routing the midi input via an AudioDeviceManager means that when a listener registers for the default midi input, this default device can be changed by the manager without the listeners having to know about it or re-register.

It also means that a listener can stay registered for a midi input that is disabled or not present, so that when the input is re-enabled, the listener will start receiving messages again.

See Also
addMidiInputCallback, isMidiInputEnabled
bool AudioDeviceManager::isMidiInputEnabled ( const String midiInputDeviceName) const

Returns true if a given midi input device is being used.

See Also
setMidiInputEnabled
void AudioDeviceManager::addMidiInputCallback ( const String midiInputDeviceName,
MidiInputCallback callback 
)

Registers a listener for callbacks when midi events arrive from a midi input.

The device name can be empty to indicate that it wants events from whatever the current "default" device is. Or it can be the name of one of the midi input devices (see MidiInput::getDevices() for the names).

Only devices which are enabled (see the setMidiInputEnabled() method) will have their events forwarded on to listeners.

Referenced by StandaloneFilterWindow::StandaloneFilterWindow().

void AudioDeviceManager::removeMidiInputCallback ( const String midiInputDeviceName,
MidiInputCallback callback 
)

Removes a listener that was previously registered with addMidiInputCallback().

Referenced by StandaloneFilterWindow::~StandaloneFilterWindow().

void AudioDeviceManager::setDefaultMidiOutput ( const String deviceName)

Sets a midi output device to use as the default.

The list of devices can be obtained with the MidiOutput::getDevices() method.

The specified device will be opened automatically and can be retrieved with the getDefaultMidiOutput() method.

Pass in an empty string to deselect all devices. For the default device, you can use MidiOutput::getDevices() [MidiOutput::getDefaultDeviceIndex()].

See Also
getDefaultMidiOutput, getDefaultMidiOutputName
String AudioDeviceManager::getDefaultMidiOutputName ( ) const

Returns the name of the default midi output.

See Also
setDefaultMidiOutput, getDefaultMidiOutput
MidiOutput* AudioDeviceManager::getDefaultMidiOutput ( ) const
noexcept

Returns the current default midi output device.

If no device has been selected, or the device can't be opened, this will return 0.

See Also
getDefaultMidiOutputName
const OwnedArray<AudioIODeviceType>& AudioDeviceManager::getAvailableDeviceTypes ( )

Returns a list of the types of device supported.

virtual void AudioDeviceManager::createAudioDeviceTypes ( OwnedArray< AudioIODeviceType > &  types)
virtual

Creates a list of available types.

This will add a set of new AudioIODeviceType objects to the specified list, to represent each available types of device.

You can override this if your app needs to do something specific, like avoid using DirectSound devices, etc.

void AudioDeviceManager::addAudioDeviceType ( AudioIODeviceType newDeviceType)

Adds a new device type to the list of types.

The manager will take ownership of the object that is passed-in.

void AudioDeviceManager::playTestSound ( )

Plays a beep through the current audio device.

This is here to allow the audio setup UI panels to easily include a "test" button so that the user can check where the audio is coming from.

void AudioDeviceManager::enableInputLevelMeasurement ( bool  enableMeasurement)

Turns on level-measuring.

When enabled, the device manager will measure the peak input level across all channels, and you can get this level by calling getCurrentInputLevel().

This is mainly intended for audio setup UI panels to use to create a mic level display, so that the user can check that they've selected the right device.

A simple filter is used to make the level decay smoothly, but this is only intended for giving rough feedback, and not for any kind of accurate measurement.

double AudioDeviceManager::getCurrentInputLevel ( ) const

Returns the current input level.

To use this, you must first enable it by calling enableInputLevelMeasurement().

See enableInputLevelMeasurement() for more info.

CriticalSection& AudioDeviceManager::getAudioCallbackLock ( )
noexcept

Returns the a lock that can be used to synchronise access to the audio callback.

Obviously while this is locked, you're blocking the audio thread from running, so it must only be used for very brief periods when absolutely necessary.

CriticalSection& AudioDeviceManager::getMidiCallbackLock ( )
noexcept

Returns the a lock that can be used to synchronise access to the midi callback.

Obviously while this is locked, you're blocking the midi system from running, so it must only be used for very brief periods when absolutely necessary.


The documentation for this class was generated from the following file: