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== File Formats ==
Digital audio can be represented by a number of different formats, which mainly pertain to the compression scheme they use(or at least support), as well as additional features such as Digital Rights Management (DRM). Almost all audio file formats support a header containing meta-data, some of which is necessary to decode them. <u>Compression</u> uses various techniques to reduce the file size of digital audio. The main concern with compression is whether it noticeably degrades the audio signal - many schemes result in a loss of quality, known as <u>lossy</u> compression. Lossy compression is based upon human perception - reducing detail in places that it is least likely be noticed. Of course, different implementations may be more noticeable than others; and many feature different settings, allowing trade-offs between the compression ratio and quality of audio. <u>Lossless</u> compression, on the other hand, results in no signal degradation, and the file can be converted back and forth from compressed and uncompressed formats without any change in the sample data. Compared to lossy compression, it typically features a much smaller compression ratio, and thus results in larger file sizes. The main formats for storing uncompressed audio are .wav (for MS Windows) and .aiff (for Apple Mac). The primary lossy compression formats are .mp3, .m4a, .ogg.
=== Wave (.wav) ===