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.
MPEG-1 is a compression and encoding system defined by MPEG (Moving Pictures Experts Group). It creates multiple frame sequences of I, B, and P, with the I frame containing all picture data. The B and P frames only store information about the changes on the last I frame. Typically, MPEG-1 uses 1.2 Mbps data rate, which is the speed rate of CD-ROM.