EVT_ACX_PEAKMETER_RETRIEVE_LEVEL callback function (acxelements.h)

Artikel
02/22/2024

The EVT_ACX_PEAKMETER_RETRIEVE_LEVEL callback function is implemented by the driver and is called when the level of a specified channel on a peakmeter node is requested.

Syntax

EVT_ACX_PEAKMETER_RETRIEVE_LEVEL EvtAcxPeakmeterRetrieveLevel;

NTSTATUS EvtAcxPeakmeterRetrieveLevel(
  ACXPEAKMETER PeakMeter,
  ULONG Channel,
  LONG *Level
)
{...}

Parameters

PeakMeter

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

Channel

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

Level

A LONG value that indicates the maximum audio signal level that occurred for the specified channel on the peakmeter node since the last time the peakmeter node was reset.

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 _CODEC_PEAKMETER_ELEMENT_CONTEXT {
    LONG            PeakMeterLevel[MAX_CHANNELS];
} CODEC_PEAKMETER_ELEMENT_CONTEXT, *PCODEC_PEAKMETER_ELEMENT_CONTEXT;

WDF_DECLARE_CONTEXT_TYPE_WITH_NAME(CODEC_PEAKMETER_ELEMENT_CONTEXT, GetCodecPeakMeterElementContext)

EVT_ACX_PEAKMETER_RETRIEVE_LEVEL    CodecR_EvtPeakMeterRetrieveLevelCallback;

NTSTATUS
NTAPI
CodecR_EvtPeakMeterRetrieveLevelCallback(
    _In_    ACXPEAKMETER    PeakMeter,
    _In_    ULONG           Channel,
    _Out_   LONG *          PeakMeterLevel
    )
{
    PAGED_CODE();

    ASSERT(PeakMeter);
    PCODEC_PEAKMETER_ELEMENT_CONTEXT peakmeterCtx = GetCodecPeakMeterElementContext(PeakMeter);
    ASSERT(peakmeterCtx);

    if (Channel == ALL_CHANNELS_ID)
    {
        Channel = 0;
    }

    *PeakMeterLevel = peakmeterCtx->PeakMeterLevel[Channel];

    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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