A stream's capabilities include whether it has a clock, if it supports seeking, and whether it supports asynchronous updating. Return Value Returns one of the following values. The ppMediaStream pointer is invalid. If a stream exists that matches the purpose ID in idPurpose , the ppMediaStream parameter points to the stream and increments its reference count. Interface Retrieves the multimedia stream's current state.
Interface Retrieves the current time from the multimedia stream's clock, if it has a clock.
Return Value Returns one of the following values. The pCurrentTime pointer is invalid. If a stream has a clock, the stream sample times are relative to the stream's clock. Return Value Returns one of the following values. One of the pointers is invalid.