Very popular mobile devices such as cellular phones, laptops, and handheld and tablet PCs are becoming more and more powerful. One of today's trends is to access multimedia services from this sort of device. Their low capacity in terms of storage, and their high inclination to wireless connection, suggest the use of streaming techniques instead of media download. Mobile devices are, at present, dramatically unhomogeneous for visualization and audio reproduction characteristics. Consequently, today multimedia delivery systems are very customized for some device profiles or for wireless connection types. Transcoding techniques are used in order to adapt the same media source to the multiple hardware profiles. Client-based transcoding techniques show their weakness in high energy consumption, and server-based transcoding techniques suffer from scalability problems. In this paper we propose a scalable distributed multimedia server based on the Grid computing paradigm, which can adapt media content to the device profile and/or to the connection link.