IPerChannelDbLevel::SetLevelAllChannels method (devicetopology.h)

The SetLevelAllChannels method sets the volume levels, in decibels, of all the channels in the audio stream.


HRESULT SetLevelAllChannels(
  [in] float [] aLevelsDB,
  [in] ULONG    cChannels,
  [in] LPCGUID  pguidEventContext


[in] aLevelsDB

Pointer to an array of volume levels. This parameter points to a caller-allocated float array into which the method writes the new volume levels, in decibels, for all the channels. The method writes the level for a particular channel into the array element whose index matches the channel number. If the audio stream contains n channels, the channels are numbered 0 to n– 1. To get the number of channels in the stream, call the IPerChannelDbLevel::GetChannelCount method.

[in] cChannels

The number of elements in the aLevelsDB array. If this parameter does not match the number of channels in the audio stream, the method fails without modifying the aLevelsDB array.

[in] pguidEventContext

Context value for the IControlChangeNotify::OnNotify method. This parameter points to an event-context GUID. If the SetLevelAllChannels call changes the state of the level control, all clients that have registered IControlChangeNotify interfaces with that control receive notifications. In its implementation of the OnNotify method, a client can inspect the event-context GUID to discover whether it or another client is the source of the control-change event. If the caller supplies a NULL pointer for this parameter, the client's notification method receives a NULL context pointer.

Return value

If the method succeeds, it returns S_OK. If it fails, possible return codes include, but are not limited to, the values shown in the following table.

Return code Description
Parameter cChannels does not equal the number of channels.
Pointer aLevelsDB is NULL.
Out of memory.


If the specified level value for any channel is beyond the range that the IPerChannelDbLevel::GetLevelRange method reports for that channel, the SetLevelAllChannels call clamps the value to the supported range and completes successfully. A subsequent call to the IPerChannelDbLevel::GetLevel method retrieves the actual value used for that channel.


Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2008 [desktop apps only]
Target Platform Windows
Header devicetopology.h

See also

IPerChannelDbLevel Interface