mp4 to jpg conversion is mostly related to attempts to turn a MPEG-4 video (.mp4) to a JPEG animated sequence of standalone .jpg images. You will need a special video to animated picture converter or utility for this, some good picks are listed below and each of them should be capable of mp4 to jpg conversion.
Open MP4 file Open JPG fileA video to picture conversion software
A multifunctional media converter for Windows