The IDistributorNotify interface is an optional interface for use by plug-in distributors to notify them of changes in the filter graph state.
When to Implement
Implement this interface when writing a plug-in distributor (PID) that is aggregated with the filter graph manager if you want the PID to receive notifications of control and changes in the composition of filter graphs.
PIDs may often use methods on the filter graph manager. During a call to an IDistributorNotify method, do not take any lock that may be held by another code path that calls the filter graph manager. To do so could result in a deadlock.
When to Use
The filter graph manager queries for this interface on any plug-in distributors that it aggregates. If found, it calls the appropriate Run, Pause, or SetSyncSource method before calling them on the IBaseFilter interface of each filter. It calls the NotifyGraphChange method whenever a filter is added or removed, or connections are changed.
Methods in Vtable Order
IUnknown methods | Description |
QueryInterface | Returns pointers to supported interfaces. |
AddRef | Increments the reference count. |
Release | Decrements the reference count. |
IDistributorNotify methods | Description |
Stop | Called when the filter graph is entering a stopped state. |
Pause | Called when the filter graph is entering a paused state. |
Run | Called when the filter graph is entering a running state. |
SetSyncSource | Called when a new clock is registered. |
NotifyGraphChange | Called when the set of filters in the filter graph change or their connections change. |
Called when the set of filters in the filter graph change or their connections change.
HRESULT NotifyGraphChange(void);
Returns an HRESULT value.
This method is called whenever an IFilterGraph::AddFilter, IFilterGraph::RemoveFilter, or IFilterGraph::ConnectDirect method is called or a method is called that will lead to one of these being called (such as IGraphBuilder::RenderFile).
Make sure you use Release on any held filters that have been removed at this point. For performance reasons, PIDs might choose not to rescan the filters until the PIDs actually need the interfaces, because there might be several separate notifications sent. However, it is important to release any cached interfaces immediately.
Called when the filter graph is entering a paused state.
HRESULT Pause(void);
Returns S_OK if the transition is complete; otherwise, returns one of the following values.
Value | Meaning |
Error value | Transition failed. |
S_FALSE | Transition is not complete, but no error has occurred. |
This method is called before the filters are notified.
Called when the filter graph is entering a running state.
HRESULT Run(
REFERENCE_TIME tStart
);
Returns an HRESULT value.
This method is called before the filters are notified.
Called when a new clock is registered.
HRESULT SetSyncSource(
IReferenceClock * pClock
);
Returns an HRESULT value.
This method is called before the filters are notified. Make sure to use AddRef on the pClock parameter if the plug-in distributor intends to hold it beyond this method call.
Called when the filter graph is entering a stopped state.
HRESULT Stop(void);
Returns S_OK if the transition is complete; otherwise, returns one of the following values.
Value | Meaning |
Error value | Transition failed. |
S_FALSE | Transition is not complete, but no error has occurred. |
This method is called before the filters are notified.
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