MPV files are MPEG-1 or MPEG-2 video files which do not contain audio streams and their alternative names for the MPEG-2 format are M1V and M2V.
This type of file can be obtained by simply renaming MPG files with the MPV extension.
The only issue about MPV files is playback, so, in case you cannot open them, you need to install the MPV Decoder to your computer.
The installation process is a little different from the typical one, but not too complicated either.
You need to extract files from the archive pack and afterwards open the Release, Release Unicode, X64 or X86 folder. Copy DLL or AX files in C:\Windows\system32, access run in the search box and type regsvr32 filename.dll or regsvr32 filename.ax.
If you are unable to install the filter, please read this small guide: How to install/uninstall DLL and AX codec files
This compact filter needs a low amount of system resources and eliminates any MPV playback problems.