Policy Persistence

This topic applies to Windows XP Home Edition and Windows XP Professional only.

Policies are either persistent or dynamic:

• The CA Manager automatically loads persistent policies from storage. Also, if you add a persistent policy to an instance of the CA Manager, DirectShow automatically adds it to every other instance of the CA Manager. (Each Video Control instance has exactly one CA Manager instance, but there can be multiple instances of the Video Control.) To support persistence, a policy must expose one of the following interfaces: IPersistStream, IPersistStorage, or IPersistPropertyBag. Also, its ICAPolicy::get_OkToPersist method must return TRUE.
• A dynamic policy exists only on the CA Manager instance where it was added. When that instance disappears, the policy also disappears. A dynamic policy must return FALSE in its ICAPolicy::get_OkToPersist method.

Typically, standalone software policies are persistent, and DirectShow filter policies are dynamic. Filters create policies when they are first added to the filter graph. They remove their policies when they leave the graph.