Classes > CoreAudioDevicesMan class > Methods > CoreAudioDevices.ChannelVolumeGet method

Remarks

Obtains the volume of a channel of the given audio endpoint device. The current channel volume can be modified through the CoreAudioDevices.ChannelVolumeSet method.

You can be notified in real-time about volume changes by catching the CallbackForCoreAudioEvents delegate having the nEvent parameter set to EV_COREAUDIO_DEVICE_VOLUME_CHANGE.

This method 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 methods related to the management of core audio devices refer to the CoreAudioDevicesMan class.

Syntax

[Visual Basic]

Public Function ChannelVolumeGet (

nDataFlow as enumCoreAudioDataFlows,

nDeviceIndex as Int16,

nChannelIndex as Integer,

nScaleType as enumVolumeScales,

ByRef fVolumeLevel as Single

) as enumErrorCodes

[C#]

public enumErrorCodes ChannelVolumeGet (

enumCoreAudioDataFlows nDataFlow,

Int16 nDeviceIndex,

Int16 nChannelIndex,

enumVolumeScales nScaleType,

ref float fVolumeLevel

);

[C++]

public: enumErrorCodes ChannelVolumeGet (

enumCoreAudioDataFlows nDataFlow,

Int16 nDeviceIndex,

Int16 nChannelIndex,

enumVolumeScales nScaleType,

float __gc *fVolumeLevel

);

Parameter

Description

nDataFlow

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.

nDeviceIndex

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

nChannelIndex

Zero-based index of the channel. The total number of channels for an audio endpoint device can be obtained through the CoreAudioDevices.ChannelCountGet method.

nScaleType

The volume scaling type.

Supported values are the following:

Mnemonic constant	Value	Meaning
SCALE_LINEAR	0	The passed volume is based upon a linear scale and can be in the range from 0.0 (silence) to 100.0 (max volume)
SCALE_LOG	1	The passed volume, expressed in dB, is based upon a logarithmic scale.

IMPORTANT NOTE ABOUT UNITS OF MEASURE:When dealing with values expressed in percentage the effective value can have different meaning depending upon the implementation of the sound card driver: for example, usually a percentage value of 100 is assumed as 0 dB: this is not the case when dealing with Core Audio API because, if the sound card driver allows applying a volume range from -100 dB (total silence) to +20 dB (sound amplification of +20 dB), a percentage value of 100 would mean that the applied volume is +20 dB. The range of volume values accepted by the sound card driver can be obtained by calling the CoreAudioDevices.MasterVolumeGet method.

IMPORTANT NOTE ABOUT CONVERSION BETWEEN UNITS OF MEASURE: When setting a volume expressed in percentage through one of our component's methods, the value displayed inside the "Sound" applet of the Control Panel may report a value slightly different respect to the one effectively set: this issue is due to a rounding problem when converting from percentage to dB (all values are stored in dB inside the driver); if this should be a problem for you, in order to avoid this minor issue you should always use dB as unit of measure when calling our component's methods and to set the "Sound" applet of the Control Panel to display values in dB instead of the percentage default.

fVolumeLevel

Reference that, on return from the method call, will contain the channel's volume level (the meaning of the returned value depends upon the nScaleType parameter)..

Return value

Value	Meaning

Negative value	An error occurred (see the LastError property for further error details)
enumErrorCodes.NOERROR (0)	The method call was successful.