mp4 to gif conversion is mostly related to attempts to create an animated .gif picture out of a video sequence, for example from MPEG-4 video (.mp4). You can find special video to GIF converters or utilities designed specially for this purpose, so these would be best way how to convert mp4 to gif.
Open MP4 file Open GIF fileA video to picture conversion software
A multifunctional media converter for Windows
A video to animated gif converter