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IMFDeviceTransform::ProcessEvent method (mftransform.h)

  • Article

The ProcessEvent method sends an event to an input stream on this Media Foundation transform (MFT).

Syntax

HRESULT ProcessEvent(
  [in] DWORD         dwInputStreamID,
  [in] IMFMediaEvent *pEvent
);

Parameters

[in] dwInputStreamID

Stream identifier. To get the list of stream identifiers, call IMFDeviceTransform::GetStreamIDs.

[in] pEvent

Pointer to the IMFMediaEvent interface of an event object.

Return value

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

Return code Description
S_OK
 The event processed successfully. The event will be propagated down stream.
MF_E_INVALIDSTREAMNUMBER
 An invalid stream ID was passed.
MF_S_TRANSFORM_DO_NO_PROPOGATE_EVENT
 Indicates that the Device MFT does not want the event to be propagated further.
E_NOTIMPL
 The function is not implemented.

Remarks

An MFT can handle sending the event downstream, or it can let the DTM do this, as indicated by the return value:

  • E_NOTIMPL: The MFT ignores all events, and the DTM should send all events downstream. After the pipeline receives this return value
  • S_OK: The MFT has examined this event, but the DTM should send the event downstream. Internally, the MFT might respond to the event in some way, or it might ignore the event.
  • MF_S_TRANSFORM_DO_NOT_PROPAGATE_EVENT: The DTM should not propagate this event downstream. Either the MFT will send the event downstream, or else the MFT will consume the event and not send it downstream. The MFT should only consume the event if the event should stop at this MFT and not travel any further downstream. But in most cases, the event should travel downstream.
To send the event downstream, the MFT adds the event to the collection object that is provided by the client in the pEvents member of the MFT_OUTPUT_DATA_BUFFER structure, when the client calls IMFTransform::ProcessOutput.

Events must be serialized with the samples that come before and after them. Attach the event to the output sample that follows the event. (The pipeline will process the event first, and then the sample.) If an MFT holds back one or more samples between calls to IMFTransform::ProcessInput and IMFTransform::ProcessOutput, the MFT should handle sending all events downstream, because in this situation the pipeline cannot correlate input samples with output samples.

If an MFT does not hold back samples and does not need to examine any events, it can return E_NOTIMPL.

Requirements

Requirement Value
Minimum supported client Windows 10, version 1703
Target Platform Windows
Header mftransform.h

See also

IMFDeviceTransform