Tom posted a comment on a wiki page

I am running Motion 4.1 and am curious why the timelapse capabilty does not allow for an mp4 choice. timelapse_codec Type: Discrete Strings Range / Valid values: mpg, mpeg4 Default: mpg Notice that the ffmpeg_video_codec Type: Discrete Strings Range / Valid values: mpeg4, msmpeg4, swf, flv, ffv1, mov, ogg, mp4, mkv, hevc Default: mpeg4 does allow mp4.