OGV is a digital video container format related to the encoding technology of the OGG Vorbis video. It can save multiple related video stream codecs like the DivX and Theora. It is these codecs that allow OGV files to open on varying media players.
MPLayer Classic VLC Media Player Jriver Media Center MPUI
M4R is a filename extension for AAC format, which is developed by Apple Inc. It is typically used to save custom iPhone ringtones from Apple iTunes. M4R can only be created from iTunes purchased songs and is usually DRM protected. It can open on iTunes, VLC Media Player, Apple QuickTime Player, and more.