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Informs the pin when to suspend processing and supplying data.
HRESULT StopAt( const REFERENCE_TIME * ptStop , BOOL bSendExtra , DWORD dwCookie );
Parameters
- ptStop
- [in] Time at which to stop streaming as specified in the REFERENCE_TIMEstructure. If you specify NULL for ptStop, it will stop immediately (no notification); if MAX_TIME, cancels stop.
- bSendExtra
- [in] Indicates whether to send an extra sample after scheduled ptStoptime.
- dwCookie
- [in] Specifies a particular value to send with the notification
when the stop occurs (used only if
ptStartif not NULL or MAX_TIME).
Return Values
Returns an HRESULTvalue that depends on the implementation of the interface.
Remarks
This method is exposed by pins that support the stopping of streams. It sets the StreamControlStateenumeration type to STREAM_DISCARDING.
In video capture, you would typically call StopAton both the output pin of a capture filter and the input pin of a multiplexer, and pay attention only to the notification from the multiplexer. This ensures that the capture filter doesn't needlessly capture extra frames, while guaranteeing that the multiplexer has, in fact, saved the last frame to a file.
In addition, you should specify TRUE for the bSendExtraparameter on the capture pin, and specify FALSE to the multiplexer pin. If an extra frame is not sent, the multiplexer will wait for the stop time indefinitely and not realize it already has received all the capture information. The multiplexer will discard the extra sample sent by the capture pin, so it will not get written to the file. Do not set bSendExtrato TRUE unless you also use IAMStreamControlon another downstream pin too, like in the preceding case.
If you call StopAtwith a time that is in the middle of a packet, the filter will deliver the whole packet before going into a discarding state. Also, if start and stop are scheduled for a single point in time, the effect is as if the start occurred an infinitesimal time before the stop. You can use this effect to capture a single frame (see CBaseStreamControlfor an implementation example).