|Microsoft DirectX 9.0|
When two filters connect, they agree on a media type, which describes the format of the data that the upstream filter will deliver. In most cases, the media type is fixed for the duration of the connection. However, DirectShow does offer limited support for filters to change the media type. When a filter switches media types, it is called a dynamic format change. If you are writing a DirectShow filter, you should be aware of the mechanisms for dynamic format changes. Even if your filter does not support such changes, it should respond correctly if another filter requests a new format.
DirectShow defines several distinct mechanisms for dynamic format changes, depending on the state of filter graph and the type of change that is required.
Otherwise, if the graph is active, but the filters in question do not support dynamic pin reconnections, there are three possible mechanisms for changing the format: