How your app generally uses gstreamer is up to you. Ideally your app will be able to use a playbin pipeline. The only requirement is that your app must use gstreamer for its audio and video needs and that it use the westerossink for its videosink. westerossink allows your video path to go through wayland so it can be manipulated by the application manager if necessary. A simple gstreamer use case is showcased in the rne-player sample app and a more real world MSE type AV player is showcased in the mse-player sample application.