mpv to mp4 conversion represents one of the variants of MPEG multimedia conversions, in this particular cases between MPEG-1 and MPEG-4 containers.
Both are actually pretty common and well supported in modern multimedia converts and video editors, so it really shouldn't be hard to find one that can be used for this. You might find more converter options under mpg to mp4 conversion.
Updated: October 16, 2023