IMFTransform::ProcessEvent method (mftransform.h)

Article
10/13/2021

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

Input stream identifier. To get the list of stream identifiers, call IMFTransform::GetStreamIDs.

[in] pEvent

Pointer to the IMFMediaEvent interface of an event object.

Return value

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.
MF_E_INVALIDSTREAMNUMBER	Invalid stream number.
MF_E_TRANSFORM_TYPE_NOT_SET	The media type is not set on one or more streams.
MF_S_TRANSFORM_DO_NOT_PROPAGATE_EVENT	The pipeline should not propagate the event.

Remarks

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

E_NOTIMPL: The MFT ignores all events, and the pipeline should send all events downstream. After the pipeline receives this return value, it might not call ProcessEvent again.
S_OK: The MFT has examined this event, but the pipeline 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 pipeline 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 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.

If MFT_UNIQUE_METHOD_NAMES is defined before including mftransform.h, this method is renamed MFTProcessEvent. See Creating Hybrid DMO/MFT Objects.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2008 [desktop apps \| UWP apps]
Target Platform	Windows
Header	mftransform.h
Library	Mfuuid.lib