CBaseStreamControl class
[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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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.]
This class implements the IAMStreamControl interface for input and output pins. It provides control over starting and stopping an individual pin on the filter. A pin that supports IAMStreamControl should inherit from this base class. The following is a typical declaration for an input pin:
class CMyInputPin : public CBaseInputPin, public CBaseStreamControl
Be sure to override NonDelegatingQueryInteface to expose IAMStreamControl. For more information, see How to Implement IUnknown.
| Public Methods | Description |
|---|---|
| CBaseStreamControl | Constructor method. |
| ~CBaseStreamControl | Destructor method. |
| CheckStreamState | Determines whether a media sample should be delivered or discarded. |
| Flushing | Notifies the base class that the pin has started or stopped flushing. |
| NotifyFilterState | Notifies the pin when the filter's state changes. |
| SetFilterGraph | Specifies the event sink for stream control events. |
| SetSyncSource | Notifies the base class of the current reference clock. |
| IAMStreamControl Methods | Description |
| GetInfo | Retrieves information about the current stream-control settings, including the start and stop times. |
| StartAt | Informs the pin when to start delivering data. |
| StopAt | Informs the pin when to stop delivering data. |
Remarks
This class requires the pin and the owning filter to notify the class when various events occur, such as the filter joining the graph or receiving a new reference clock. You should call the following class methods:
- In the filter's IMediaFilter::SetSyncSource method, call the CBaseStreamControl::SetSyncSource method. This method notifies the class of the current reference clock.
- In the filter's CBaseFilter::JoinFilterGraph method, call the CBaseStreamControl::SetFilterGraph method. This method gives the class a pointer to the Filter Graph Manager, so that the class can send the right stream-control events.
- Whenever the filter changes state (to running, paused, or stopped), call the CBaseStreamControl::NotifyFilterState method.
- In the pin's IPin::BeginFlush and IPin::EndFlush methods, call the CBaseStreamControl::Flushing method.
The CBaseStreamControl class uses the filter graph's reference clock to determine which samples the filter should be deliver, and which it should discard. In your pin's IMemInputPin::Receive method, call the CBaseStreamControl::CheckStreamState method with a pointer to the incoming media sample. If the method returns the value STREAM_FLOWING, deliver the sample downstream. Otherwise, discard it.
Requirements
| Requirement | Value |
|---|---|
| Header |
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| Library |
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