How to convert .mp4 videos to .m1v format.
Converting MPEG-4 Videos directly to MPEG-1 Video Files (.mp4 to .m1v conversion) is certainly possible and quite straightforward.
Use one of several video editing programs or (online) conversion tools, such as Adobe Premiere Pro or Freemake Video Converter, which allow users to import MP4 videos and export them in M1V format.