Bringing much new functionality, MPEG-4 is expected to be the future standard for multimedia applications. However, these numerous capabilities imply a complex authoring process, requiring many different competencies from audio/visual/BIFS encoding to the different delivery scenarios: local access on CD/DVD-ROM, Internet or broadcast. From multimedia history, we can see that however powerful the technologies underlying multimedia computing, it is the authoring suite(s) that determines the success of these systems. From this assumption, our solution for an MPEG-4 authoring system has focused mainly on two aspects: provide a powerful interface for an MPEG-4 author and define an open and modular architecture able to progress with MPEG-4 versions and easily extensible with better and higher-level authoring features.