As the name says MPV Decoder (aka Mpeg2DecFilter) will help to decode MPV files.
What is MPV?
MPV is a MPEG-1 or MPEG-2 video elemantary stream (no audio). Also called M1V for MPEG-1 video and M2V for MPEG-2 video.
Sometimes you can just rename the files .mpg and play them in Windows Media Player or other DirectShow player. However, if you get errors about not being able to play them, install MPV Decoder.
How to install MPV Decoder
If you are unable to install the filter, please read this small guide: How to install/uninstall DLL and AX codec files