EC_ACTIVATE (Compact 2013)
An audio or video renderer is losing or gaining activation.
The audio or video renderer sends this event notification.
Set to 1 if activation gained, or 0 if lost.
Pointer to the IBaseFilter interface that is sending the event notification.
This event notification is not sent to the application.
This notification is used for sound-follows-focus and full-screen switching.
To interact in full-screen protocols, a video renderer should send an EC_ACTIVATE notification whenever its window is either activated or deactivated.
In other words, an EC_ACTIVATE notification should be sent for each WM_ACTIVATEAPP message received by a renderer.
For information on how to use this event code, see CBaseFilter::NotifyEvent.