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UID title description helpviewer_keywords old-location tech.root ms.assetid ms.date ms.keywords req.header req.include-header req.target-type req.target-min-winverclnt req.target-min-winversvr req.kmdf-ver req.umdf-ver req.ddi-compliance req.unicode-ansi req.idl req.max-support req.namespace req.assembly req.type-library req.lib req.dll req.irql targetos req.typenames req.redist ms.custom f1_keywords dev_langs topic_type api_type api_location api_name
NF:mfobjects.IMFAsyncCallback.GetParameters
IMFAsyncCallback::GetParameters (mfobjects.h)
Provides configuration information to the dispatching thread for a callback. (IMFAsyncCallback.GetParameters)
374dd139-d3e7-45d0-a7d3-1187b928ef57
GetParameters
GetParameters method [Media Foundation]
GetParameters method [Media Foundation]
IMFAsyncCallback interface
IMFAsyncCallback interface [Media Foundation]
GetParameters method
IMFAsyncCallback.GetParameters
IMFAsyncCallback::GetParameters
MFASYNC_BLOCKING_CALLBACK
MFASYNC_FAST_IO_PROCESSING_CALLBACK
MFASYNC_REPLY_CALLBACK
MFASYNC_SIGNAL_CALLBACK
Zero
mf.imfasynccallback_getparameters
mfobjects/IMFAsyncCallback::GetParameters
mf\imfasynccallback_getparameters.htm
mf
374dd139-d3e7-45d0-a7d3-1187b928ef57
12/05/2018
374dd139-d3e7-45d0-a7d3-1187b928ef57, GetParameters, GetParameters method [Media Foundation], GetParameters method [Media Foundation],IMFAsyncCallback interface, IMFAsyncCallback interface [Media Foundation],GetParameters method, IMFAsyncCallback.GetParameters, IMFAsyncCallback::GetParameters, MFASYNC_BLOCKING_CALLBACK, MFASYNC_FAST_IO_PROCESSING_CALLBACK, MFASYNC_REPLY_CALLBACK, MFASYNC_SIGNAL_CALLBACK, Zero, mf.imfasynccallback_getparameters, mfobjects/IMFAsyncCallback::GetParameters
mfobjects.h
Mfidl.h
Windows
Windows Vista [desktop apps \| UWP apps]
Windows Server 2008 [desktop apps \| UWP apps]
Mfuuid.lib
Windows
19H1
IMFAsyncCallback::GetParameters
mfobjects/IMFAsyncCallback::GetParameters
c++
APIRef
kbSyntax
COM
mfuuid.lib
mfuuid.dll
IMFAsyncCallback.GetParameters

IMFAsyncCallback::GetParameters

-description

Provides configuration information to the dispatching thread for a callback.

-parameters

-param pdwFlags [out]

Receives a flag indicating the behavior of the callback object's IMFAsyncCallback::Invoke method. The following values are defined. The default value is zero.

Value Meaning
Zero
The callback does not take a long time to complete, but has no specific restrictions on what system calls it makes. The callback generally takes less than 30 milliseconds to complete.
MFASYNC_FAST_IO_PROCESSING_CALLBACK
The callback does very minimal processing. It takes less than 1 millisecond to complete.

The callback must be invoked from one of the following work queues:

  • MFASYNC_CALLBACK_QUEUE_IO
  • MFASYNC_CALLBACK_QUEUE_TIMER
MFASYNC_SIGNAL_CALLBACK
Implies MFASYNC_FAST_IO_PROCESSING_CALLBACK, with the additional restriction that the callback does no processing (less than 50 microseconds), and the only system call it makes is SetEvent.

The callback must be invoked from one of the following work queues:

  • MFASYNC_CALLBACK_QUEUE_IO
  • MFASYNC_CALLBACK_QUEUE_TIMER
MFASYNC_BLOCKING_CALLBACK
Blocking callback.
MFASYNC_REPLY_CALLBACK
Reply callback.

-param pdwQueue [out]

Receives the identifier of the work queue on which the callback is dispatched.

This value can specify one of the standard Media Foundation work queues, or a work queue created by the application. For list of standard Media Foundation work queues, see Work Queue Identifiers. To create a new work queue, call MFAllocateWorkQueue. The default value is MFASYNC_CALLBACK_QUEUE_STANDARD.

If the work queue is not compatible with the value returned in pdwFlags, the Media Foundation platform returns MF_E_INVALID_WORKQUEUE when it tries to dispatch the callback. (See MFPutWorkItem.)

-returns

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code Description
S_OK
The method succeeded.
E_NOTIMPL
Not implemented. Assume the default behavior.

-remarks

The GetParameters method returns information about the callback so that the dispatching thread can optimize the process that it uses to invoke the callback.

If the method returns a value other than zero in the pdwFlags parameter, your Invoke method must meet the requirements described here. Otherwise, the callback might delay the pipeline.

If you want default values for both parameters, return E_NOTIMPL. The default values are given in the parameter descriptions on this page.

This interface is available on the following platforms if the Windows Media Format 11 SDK redistributable components are installed:

  • Windows XP with Service Pack 2 (SP2) and later.
  • Windows XP Media Center Edition 2005 with KB900325 (Windows XP Media Center Edition 2005) and KB925766 (October 2006 Update Rollup for Windows XP Media Center Edition) installed.

-see-also

Asynchronous Callback Methods

IMFAsyncCallback

Work Queues