Microsoft DirectX 8.0 |
Blocks data flow from an active output pin. This interface is exposed by output pins that can reconnect dynamically. Use this interface to start a dynamic reconnection within the filter graph. For more information, see Dynamic Graph Building.
Filter developers: Parser and capture filters that support dynamic reconnection should support this interface on their output pins. Generally, other types of filters do not need to implement this interface.
IUnknown methods Description QueryInterface Retrieves pointers to supported interfaces. AddRef Increments the reference count. Release Decrements the reference count. IPinFlowControl methods Description Block Blocks or unblocks the flow of data from the pin.
Blocks or unblocks the flow of data from the pin.
Syntax
HRESULT Block( DWORD dwBlockFlags, HANDLE hEvent, );
Parameters
- dwBlockFlags
- [in] Flag that indicates whether to block or unblock the pin. Must be one of the following values:
- Zero: Unblock data flow from the pin.
- AM_PIN_FLOW_CONTROL_BLOCK: Block data flow from the pin.
- hEvent
- [in] Handle to an event object, or NULL. If this parameter is non-NULL, the method is asynchronous and returns immediately. The event is signaled when the operation completes. If this parameter is NULL, the method is synchronous and does not complete until the pin is blocked. If dwBlockFlags is zero, this parameter must be NULL.
Return Value
Returns an HRESULT value. Possible values include the following.
S_FALSE Pin is already unblocked. S_OK Success. VFW_E_PIN_ALREADY_BLOCKED Pin is already blocked on another thread. VFW_E_PIN_ALREADY_BLOCKED_ON_THIS_THREAD Pin is already blocked on the calling thread.
Remarks
This method can be synchronous or asynchronous:
- To call it asynchronously, use the CreateEvent function to create an event object. Pass the event handle in the hEvent parameter. The method returns immediately and signals the event when the operation has completed. Call a wait function such as WaitForSingleObject to wait for the event.
- To call this method synchronously, set the hEvent parameter to NULL. The method blocks until it completes. The method might not complete until the pin is ready to deliver a sample. If the filter is paused, the method might block indefinitely. Therefore, you should not call this method synchronously from your main application thread.