EVT_ACX_STREAMAUDIOENGINE_RETRIEVE_PRESENTATION_POSITION callback function (acxelements.h)

Article
02/22/2024

The EVT_ACX_STREAMAUDIOENGINE_RETRIEVE_PRESENTATION_POSITION callback function is implemented by the driver and is called to retrieve the current position within the audio data being rendered to the stream audio engine node.

Syntax

EVT_ACX_STREAMAUDIOENGINE_RETRIEVE_PRESENTATION_POSITION EvtAcxStreamaudioengineRetrievePresentationPosition;

NTSTATUS EvtAcxStreamaudioengineRetrievePresentationPosition(
  ACXSTREAMAUDIOENGINE StreamAudioEngine,
  PULONGLONG PositionInBlocks,
  PULONGLONG QPCPosition
)
{...}

Parameters

StreamAudioEngine

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

PositionInBlocks

Specifies the block offset from the start of the stream to the current post-decoded, uncompressed position in the stream. See KSAUDIO_PRESENTATION_POSITION structure for more information on this value.

QPCPosition

Specifies the value of the performance counter at the time that the audio driver reads the presentation position in response to the callback. See KSAUDIO_PRESENTATION_POSITION structure for more information on this value.

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.

EVT_ACX_STREAMAUDIOENGINE_RETRIEVE_PRESENTATION_POSITION    CodecR_EvtAcxStreamAudioEngineRetrievePresentationPosition;

NTSTATUS
CodecR_EvtAcxStreamAudioEngineRetrievePresentationPosition(
    _In_    ACXSTREAMAUDIOENGINE    StreamAudioEngine,
    _Out_   PULONGLONG              PositionInBlocks,
    _Out_   PULONGLONG              QPCPosition
)
{
    NTSTATUS status = STATUS_INVALID_PARAMETER;
    ACXSTREAM stream;
    PCODEC_STREAM_CONTEXT ctx;
    CRenderStreamEngine * streamEngine = NULL;

    PAGED_CODE();

    stream = AcxStreamAudioEngineGetStream(StreamAudioEngine);
    if (stream)
    {
        ctx = GetCodecStreamContext(stream);

        streamEngine = static_cast<CRenderStreamEngine*>(ctx->StreamEngine);

        status = streamEngine->GetPresentationPosition(PositionInBlocks, QPCPosition);
    }

    return status;
}

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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