DVR-MS, also called Microsoft Digital Video Recording, is a digital audio and video file container format introduced by Microsoft in 2004. It features a .dvr.ms filename extension and is used to save TV data recorded using Windows 7, Windows Vista, and Windows XP Media Center Edition. It stores both audio and video data wrapped inside an ASF container.
Windows Media Player Windows Media Center CyberLink PowerDVD 17
M4B is an audio filename extension for AAC format, which is developed by Apple Inc. It is mainly used on podcast and audiobook files. Typically, M4B files contain audio and other metadata like images, hyperlinks, and chapter markers. M4B files are DRM copy-protected and can be opened on Apple iTunes and QuickTime Player.