And the no video, no audio or video audio out of sync problem is also a big headache.
MP4 format is encoded with MPEG-4, H.265, H.264, etc but Windows Media Player before version 12 can normally play H.264 files so Windows Media Player not playing MP4 is an occasional case. For specific media players like Windows Media Player and VLC, you'd better download MP4 codec from their official website to ensure the safety of the codec pack.
