CUE is a text file that describes how tracks are arranged in a super-audio CD and DVDs. Typically, CUE sheets come in plain text and have a filename extension of .cue. Today, this format is prevalent in most media players and optical disc authoring apps.
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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.