EVT_ACX_VOLUME_ASSIGN_LEVEL callback function (acxelements.h)

Artikel
02/22/2024

The EVT_ACX_VOLUME_ASSIGN_LEVEL callback function is implemented by the driver and is called when the volume level of a channel is set for a volume node.

Syntax

EVT_ACX_VOLUME_ASSIGN_LEVEL EvtAcxVolumeAssignLevel;

NTSTATUS EvtAcxVolumeAssignLevel(
  ACXVOLUME Volume,
  ULONG Channel,
  LONG VolumeLevel
)
{...}

Parameters

Volume

An existing, initialized, ACXVOLUME object. For more information about ACX objects, see Summary of ACX Objects.

Channel

A ULONG referring to a channel on the specified volume node. If this value is -1, then it refers to the master channel which represents the volume level for all channels on the volume node.

VolumeLevel

A LONG value that specifies the volume level of a channel in a volume node. If the channel value is -1 (referring to the master channel), then all channels on this volume node will be set to this volume level. Volume level values use the following scale:

-2147483648 is -infinity decibels (attenuation),

-2147483647 is -32767.99998474 decibels (attenuation), and

+2147483647 is +32767.99998474 decibels (gain).

Return value

Returns STATUS_SUCCESS if the call was successful. Otherwise, it returns an appropriate error code. For more information, see Using NTSTATUS Values.

Remarks

Example

Example usage is shown below.

typedef struct _VOLUME_ELEMENT_CONTEXT {
    LONG            VolumeLevel[MAX_CHANNELS];
} VOLUME_ELEMENT_CONTEXT, *PVOLUME_ELEMENT_CONTEXT;

WDF_DECLARE_CONTEXT_TYPE_WITH_NAME(VOLUME_ELEMENT_CONTEXT, GetVolumeElementContext)

EVT_ACX_VOLUME_ASSIGN_LEVEL         CodecC_EvtVolumeAssignLevelCallback;

NTSTATUS
CodecC_EvtVolumeAssignLevelCallback(
    _In_    ACXVOLUME   Volume,
    _In_    ULONG       Channel,
    _In_    LONG        VolumeLevel
)
{
    PAGED_CODE();

    ASSERT(Volume);
    PVOLUME_ELEMENT_CONTEXT volumeCtx = GetVolumeElementContext(Volume);
    ASSERT(volumeCtx);

    if (Channel != ALL_CHANNELS_ID)
    {
        volumeCtx->VolumeLevel[Channel] = VolumeLevel;
    }
    else
    {
        for (ULONG i = 0; i < MAX_CHANNELS; ++i)
        {
            volumeCtx->VolumeLevel[i] = VolumeLevel;
        }
    }

    return STATUS_SUCCESS;
}

ACX requirements

Minimum ACX version: 1.0

For more information about ACX versions, see ACX version overview.

Requirements

Requirement	Value
Header	acxelements.h
IRQL	PASSIVE_LEVEL

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