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Windows Driver Kit DDI reference (nc-acxstreams-evt_acx_stream_pause)

Description

The EvtAcxStreamPause event tells the driver to transition the stream state from Run to Pause.

Parameters

`Stream`

An ACXSTREAM object represents an audio stream created by a circuit. The stream is composed of a list of elements created based on the parent circuit's elements. For more information, see ACX - Summary of ACX Objects.

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

An AcxStream supports different states. These states indicate when audio is flowing (RUN state), audio is not flowing but audio hardware is prepared (PAUSE state), or audio is not flowing and audio hardware is not prepared (STOP state).

The EvtAcxStreamPause event will transition the stream state from the Run state to the Pause state. Once the stream is in the Pause state, the driver may receive the EvtAcxStreamRun event to transition to the Run state or the driver may receive the EvtAcxStreamReleaseHardware event to transition to the Stop state.

During ACX device power down and removal, if streams are present, ACX will call the EvtAcxStreamPause to transition streams to Pause. This is Stream Instance scoped.

ACX Events are analogous to KS states as described in this table.

Start State	End State	ACX Driver Event Called	Notes
STOP	ACQUIRE	PrepareHardware	Driver performs hardware allocations and preparations
ACQUIRE	PAUSE	(No Call)
PAUSE	RUN	Run
RUN	PAUSE	Pause
PAUSE	ACQUIRE	(No call)
ACQUIRE	STOP	ReleaseHardware	Driver releases hardware allocations

Example

Example usage is shown below.

    ACX_STREAM_CALLBACKS streamCallbacks;
    ACX_STREAM_CALLBACKS_INIT(&streamCallbacks);
    streamCallbacks.EvtAcxStreamPause = EvtStreamPause;
    ...
    status = AcxStreamInitAssignAcxStreamCallbacks(StreamInit, &streamCallbacks);

#pragma code_seg("PAGE")
NTSTATUS
EvtStreamPause(
    _In_ ACXSTREAM Stream
    )
{
    PSTREAM_CONTEXT ctx;
    NTSTATUS        status = STATUS_SUCCESS;

    PAGED_CODE();

    ctx = GetStreamContext(Stream);

    status = TransitionStreamToPause(Stream);

    ctx->StreamState = AcxStreamStatePause;

    return status;
}

ACX requirements

Minimum ACX version: 1.0

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

EVT_ACX_STREAM_PAUSE - NtDoc