BeginFlush method begins a flush operation.
This method has no parameters.
Returns S_OK or another HRESULT value.
At the start of a flush operation, the input pin's CTransformInputPin::BeginFlush method calls this method. This method passes the
BeginFlush call downstream.
If the derived class uses a worker thread to deliver samples, it should discard any queued data during a flush operation. That can be done either in the
BeginFlush method, or in the EndFlush method. However, note that calls to
BeginFlush are not synchronized with the streaming thread. If the
BeginFlush method discards the queued data, the filter must be careful not to process any more data between the
BeginFlush and EndFlush calls. For more information, see Data Flow for Filter Developers.