IPin::BeginFlush method (strmif.h)

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The BeginFlush method begins a flush operation.

Applications should not call this method. This method is called by other filters, to flush data from the graph.

Syntax

HRESULT BeginFlush();

Return value

Returns an HRESULT value. Possible values include the following.

Return code	Description
S_OK	Success.
E_UNEXPECTED	The pin is an output pin.

Remarks

Call this method only on input pins. Output pins return E_UNEXPECTED.

In a flush operation, a filter discards whatever data it was processing. It rejects new data until the flush is completed. The flush is completed when the upstream pin calls the IPin::EndFlush method. Flushing enables the filter graph to be more responsive when events alter the normal data flow. For example, flushing occurs during a seek.

When BeginFlush is called, the filter performs the following steps:

1. Passes the IPin::BeginFlush call downstream.
2. Sets an internal flag that causes all data-streaming methods to fail, such as IMemInputPin::Receive.
3. Returns from any blocked calls to the Receive method.

When the BeginFlush notification reaches a renderer filter, the renderer frees any samples that it holds.

After BeginFlush is called, the pin rejects all samples from upstream, with a return value of S_FALSE, until the IPin::EndFlush method is called.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	strmif.h (include Dshow.h)
Library	Strmiids.lib

See also

Data Flow in the Filter Graph

Error and Success Codes

IPin Interface