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Understanding Digital Audio

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File Formats
'''Digital Rights Management''' (DRM) refers to various methods that attempt to restrict decoding media files to authorized devices/users, preventing unlicensed file sharing and piracy. Many web stores still use forms of DRM, although it is now less common for music. DRM typically only allows playback through approved devices and software. No standardized, cross-brand DRM scheme was ever adapted, leading to significant consumer frustration. At the same time, most schemes were easily defeated. Thus, most of the music industry abandoned its use around 2009.
=== File Extensions/Specific Formats ===
The main formats for storing uncompressed audio are .wav (for MS Windows), .aiff (for Apple Mac), and .au (Java, Unix). The primary lossy compression formats are .mp3, .m4a, .ogg, .aac, and .wma. A popular lossless file types is .flac. Windows media audio (.wma) supports both lossy and lossless encoding; however, it is generally assumed to use the lossy codec. .m4p and .wma are the primary formats of DRM-enabled audio files - iTunes switched from .m4p to .m4a files when it stopped using DRM. Almost all of these file types are capable of additional audio formats; however, these are their most common usages, and you can assume the type of audio contained in the file from the file type.