Classes > CoreAudioDevicesMan class > Methods > CoreAudioDevices.PartsVolumeGet method

Remarks

Obtains the volume of a given channel for the given subpart of the given audio endpoint device. The current level for the same part can be modified through the CoreAudioDevices.PartsVolumeSet method.

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 PartsVolumeGet (

nDataFlow as enumCoreAudioDataFlows,

nDeviceIndex as Int32,

nPartIndex as Int32,

nScaleType as enumVolumeScales,

nChannel as Int32,

ByRef fVolumeLevel as Single

) as enumErrorCodes

[C#]

public enumErrorCodes PartsVolumeGet (

enumCoreAudioDataFlows nDataFlow,

Int32 nDeviceIndex,

Int32 nPartIndex,

enumVolumeScales nScaleType,

Int32 nChannel,

ref float fVolumeLevel

);

[C++]

public: enumErrorCodes PartsVolumeGet (

enumCoreAudioDataFlows nDataFlow,

Int32 nDeviceIndex,

Int32 nPartIndex,

enumVolumeScales nScaleType,

Int32 nChannel,

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 render or capture audio endpoint devices can be obtained through the CoreAudioDevices.CountGet method passing DEVICE_DATA_FLOW_RENDER or DEVICE_DATA_FLOW_CAPTURE to the nDataFlow parameter.

nPartIndex

Zero-based index of the requested subpart. The total number of available subparts can be obtained through the CoreAudioDevices.PartsCountGet 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.PartsVolumeRangeGet 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 the fact that the algorithm used by the sound applet for converting from percentage to dB is undocumented (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.

nChannel

Zero-based index of the channel. The total number of channels can be obtained through the CoreAudioDevices.PartsChannelsCountGet method.

If this value is set to -1 the returned value represents the maximum available volume level among the existing channels.

fVolumeLevel

Reference that, on return from the method call, will contain the volume level expressed in the selected volume scaling type.

Return value

Value	Meaning

Negative value	An error occurred, check the LastError property value in order to get the error code
enumErrorCodes.ERR_NOERROR (0)	The method call was successful