WTV (Windows Recorded TV Show File) is a video format recorded using Windows Media Center (WMC). WMC is a program for recording TV shows and playing multimedia content. WTV uses the MPEG-2 compression standard for videos and Dolby Digital AC-3 or MPEG-1 Layer II for audio. Some WTV files might include metadata as well as DRM protection.
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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.