IsSpecialSample method determines whether queued data is a control message.
BOOL IsSpecialSample( IMediaSample *pSample );
Pointer to an item in the queue.
Returns TRUE if pSample is a control message, or FALSE otherwise.
The COutputQueue::QueueSample method can receive control messages in addition to media samples. A control message is a defined constant (cast to a LONG_PTR type) that instructs the thread to perform an action. Control messages do not contain media data. For more information, see COutputQueue::QueueSample.