It is very unlikely that any way exists to achieve xspf to mp4 conversion, i.e. convert convert .xspf playlists to MP4 multimedia format.
Playlists are just special text files that contain sequence of the actual .mp4 (or other audio) files to be played. At best, you can check the .xspf file using a text editor and see where the actual audio files are located, but usually these are located within the same folder.