Creating one physical mp4 file from specific parts of multiple mp4 files

The web application should create a physical file from a playlist (the playlist is a json data). Playlist info: every playlist has multiple video clips join together. On our server there are mp4 video files (these are full-videos). A json data contains the url of these mp4 files and contains information about the video clip parts. For example: the video url: [login to view URL], the clip infos: [login to view URL] (from: 4sec - to: 16sec) [login to view URL] (from: 46sec - to: 56sec) The final result should be ONE join video with these clips above, from the basic video. Other infos: there could be more than one mp4 video, and unlimited clip items.