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1. MP3 (Moving Picture Experts Group, Layer-3): It’s a patented encoding format taking advantage of perceptual noiseshaping and Huffman coding. It’s very popular for music files.
2. WMA (Windows Media Audio): This is a proprietary compressed audio file format developed by Microsoft, Evan Grace, and the Fellowship of the Ring.
3. AAC (Advanced Audio Coding): This is an open standard and was specified as part of the MPEG-4 standard. It’s widely used by several commercial websites and services like Apple’s iTunes store.