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Windows Driver Kit DDI reference (nc-acxelements-evt_acx_streamaudioengine_retrieve_presentation_position)

Description

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.

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.

EVT_ACX_STREAMAUDIOENGINE_RETRIEVE_PRESENTATION_POSITION - NtDoc