Events for Visual Basic 6 COM interoperability

Remarks

Occurs each time an event generated by CoreAudio devices occurs.

This event replaces the usage of the CallbackForCoreAudioEvents delegate and is only intended for usage with applications developed using Visual Basic 6 (which results unreliable when dealing with delegates and callbacks) and, in order to be enabled, requires a call to the COMEventEnable method with the nEventType parameter set to EVENT_TYPE_COREAUDIO.

This event is only intended for usage with Windows Vista and later versions: further information about management of audio devices in Windows Vista and later versions can be found inside the How to access settings of audio devices in Windows Vista and later versions tutorial.

For further details about callback delegates see the How to synchronize the container application with the API tutorial.

Syntax

[Visual Basic 6]

Private Sub DjStudioApi_OnCoreAudioEvents ( _

ByVal nEvent as enumCoreAudioEvents, _

ByVal nData1 as Long, _

ByVal nData2 as Long, _

ByVal nData3 as Long _

)

where "DjStudioApi" is declared in Visual Basic 6 code as:

Dim WithEvents DjStudioApi As AudioDjStudioApi.AudioDjStudioApiObj

Event Data

Parameter

Description

nEvent

Event reported by the CoreAudio device.

Supported values are the following:

Mnemonic constant

Value

Meaning with data parameters

EV_COREAUDIO_DEVICE_STATE_CHANGED

Occurs when the state of an audio endpoint device changes. The current status of an audio endpoint device could be also queried using the CoreAudioDevices.StatusGet method..

Involved data parameters:

nData1: Zero-based index of the audio endpoint device which generated the event. The total number of audio endpoint devices can be obtained through the CoreAudioDevices.CountGet method.

When this parameter is set to -1 the application is notified about the fact that the status of one of the audio endpoint devices not previously enumerated through the call to the CoreAudioDevices.Enum method (for example a disabled device which become active and ready) has now changed its status so it could be worth calling again the CoreAudioDevices.Enum method in order to update the list of available audio endpoint devices.

nData2: Direction in which audio data flows between an audio endpoint device and an application. Supported values are the following:

Mnemonic Value	Value	Meaning
DEVICE_DATA_FLOW_RENDER	0	Audio rendering stream. Audio data flows from the application to the audio endpoint device, which renders the stream
DEVICE_DATA_FLOW_CAPTURE	1	Audio capture stream. Audio data flows from the audio endpoint device that captures the stream, to the application.

nData3: New status assumed by the audio endpoint device. The returned value can be a combination of the following flags:

Mnemonic Value	Value	Meaning
DEVICE_STATE_ACTIVE	1	The device is active
DEVICE_STATE_DISABLED	2	The device is disabled
DEVICE_STATE_NOTPRESENT	4	The device is not present: the audio endpoint device is considered "not present" when the audio adapter has been installed and configured inside the system but it was physically removed at a later time: quite typical situation with devices connected through USB.
DEVICE_STATE_UNPLUGGED	8	The device is unplugged: the audio endpoint device is considered "unplugged" when the audio adapter that contains the jack for the endpoint device is present and enabled, but the endpoint device is not plugged into the jack

EV_COREAUDIO_DEVICE_ADDED

Occurs when a new audio endpoint device is added to the system. After catching this event you can get the updated list of available audio endpoint devices by calling again the CoreAudioDevices.Enum method.

Involved data parameters: none.

EV_COREAUDIO_DEVICE_REMOVED

Occurs when a new audio endpoint device is removed from the system. After catching this event you can get the updated list of available audio endpoint devices by calling again the CoreAudioDevices.Enum method.

Involved data parameters: none.

EV_COREAUDIO_DEVICE_DEFAULT_CHANGE

Occurs when the system defined default audio endpoint device changes. The current system default device can be also queried using the CoreAudioDevices.DefaultGet method..

By design this event is only sent to the first instance of the component.

Involved data parameters:

nData1: Zero-based index of the audio endpoint which is now the system default for the role set into the nRole parameter. The total number of audio endpoint devices can be obtained through the CoreAudioDevices.CountGet method.

This parameter may be set to -1 in case the device should have been unplugged from the system when the previous enumeration occurred, for example because an USB device was installed but not plugged in.

nData2: Direction in which audio data flows between an audio endpoint device and an application. Supported values are the following:

Mnemonic Value	Value	Meaning
DEVICE_DATA_FLOW_RENDER	0	Audio rendering stream. Audio data flows from the application to the audio endpoint device, which renders the stream
DEVICE_DATA_FLOW_CAPTURE	1	Audio capture stream. Audio data flows from the audio endpoint device that captures the stream, to the application.

nData3: The role that the system has assigned to the audio endpoint device that became the new system default. Supported values are the following:

Mnemonic Value	Value	Meaning
DEVICE_ROLE_CONSOLE	0	Games, system notification sounds, and voice commands
DEVICE_ROLE_MULTIMEDIA	1	Music, movies, narration, and live music recording
DEVICE_ROLE_COMMUNICATIONS	2	Voice communications

EV_COREAUDIO_DEVICE_VOLUME_CHANGE

Occurs when the volume level of an audio endpoint device changes. After receiving this event you can query current volume through the CoreAudioDevices.ChannelVolumeGet and CoreAudioDevices.MasterVolumeGet methods.

Involved data parameters:

nData1: Zero-based index of the audio endpoint device which generated the event. The total number of audio endpoint devices can be obtained through the CoreAudioDevices.CountGet method.

nData2: Direction in which audio data flows between an audio endpoint device and an application. Supported values are the following:

Mnemonic Value	Value	Meaning
DEVICE_DATA_FLOW_RENDER	0	Audio rendering stream. Audio data flows from the application to the audio endpoint device, which renders the stream
DEVICE_DATA_FLOW_CAPTURE	1	Audio capture stream. Audio data flows from the audio endpoint device that captures the stream, to the application.

EV_COREAUDIO_DEVICE_VUMETER_CHANGE

Occurs when the VU-Meter level of an audio endpoint device changes. After receiving this event you can query current peak values through the CoreAudioDevices.VuMeterMasterPeakValueGet and CoreAudioDevices.VuMeterChannelPeakValueGet methods.

Involved data parameters:

nData1: Zero-based index of the audio endpoint device which generated the event. The total number of audio endpoint devices can be obtained through the CoreAudioDevices.CountGet method.

nData2: Direction in which audio data flows between an audio endpoint device and an application. Supported values are the following:

Mnemonic Value	Value	Meaning
DEVICE_DATA_FLOW_RENDER	0	Audio rendering stream. Audio data flows from the application to the audio endpoint device, which renders the stream
DEVICE_DATA_FLOW_CAPTURE	1	Audio capture stream. Audio data flows from the audio endpoint device that captures the stream, to the application.

EV_COREAUDIO_SESSION_VOLUME_CHANGE

Occurs when the volume or the mute status of the current session is modified through the Windows Mixer.

Involved data parameters:

nData1: The new volume, can be a value between 0 and 100

nData2: :The new mute status.

Supported values are the following:

Value	Meaning
0	The session volume is not muted.
1	The session volume is muted.

EV_COREAUDIO_DEVICE_PART_CHANGE

Occurs when the volume or mute status of a specific subpart of an audio endpoint device is modified by the user inside the Sound applet of the Windows Control Panel.

In order to obtain the updated volume levels and mute status, use the CoreAudioDevices.PartsVolumeGet and CoreAudioDevices.PartsMuteGet method in conjunction with the parameters passed to the event..

Involved data parameters:

nData1: Zero-based index of the audio endpoint device whose subpart generated the event. The total number of audio endpoint devices can be obtained through the CoreAudioDevices.CountGet method.

nData2: Direction in which audio data flows between an audio endpoint device and an application. Supported values are the following:

Mnemonic Value	Value	Meaning
DEVICE_DATA_FLOW_RENDER	0	Audio rendering stream. Audio data flows from the application to the audio endpoint device, which renders the stream
DEVICE_DATA_FLOW_CAPTURE	1	Audio capture stream. Audio data flows from the audio endpoint device that captures the stream, to the application.

nData1

First 32 bits integer value containing event specific data; its value and meaning depends upon the specific event received: see the table above for possible values.

nData2

Second 32 bits integer value containing event specific data; its value and meaning depends upon the specific event received: see the table above for possible values.

nData3

Third 32 bits integer value containing event specific data; its value and meaning depends upon the specific event received: see the table above for possible values.