This paper describes an approach for optimizing media streaming services in mobile environments by utilizing the fifth-generation mobile network technology (5G), including millimeter Wave (mmWave) high speed data links, 5G Edge Computing and relevant state-of-the-art media streaming standards, such as Network Based Media Processing (NBMP) and Server and Network Assisted DASH (MPEG SAND). Although the solution described in this paper can be applied to media streaming in various mobility scenarios, the focus of this work is on rail environments and allowing video-on-demand (VoD) catalogues (Mediatheks) to be made available to train passengers via regular VoD apps – even when trains are not connected to the Internet. To achieve this objective, we introduce caching nodes inside trains and their respective stations. The work presented in this paper will be trialed in a railway station in Berlin, as part of the EU-funded research project, 5G-VICTORI.