CAF is a highly specialized audio file format. It was developed by Apple Computer, its name is an abbreviation for Core Audio File. It is a container format for audio files. CAF is distinguished by its large size from many other similar audio file formats. At the same time, the compression ratio is, on the contrary, much less than that of files of a different format, which allows compression without loss of quality compared to the original. The disadvantages of the CAF format are that not all popular players support it, and therefore such files need to be converted.
AU is an audio file format created in Audacity. This is a free cross-platform program designed to edit audio files. AU format (Audio Units) was developed by Sun Microsystems. This format greatly simplifies the task of reliable storage of audio files. An AU file consists of 3 parts: a header (max. 24 bytes), a description block of various sizes, and audio data. The file format is used on computers running the Sun or Unix operating system. However, it opens with other audio players. The AU format uses the logarithmic encoding method, previously very popular on computers running the Sun SPARCstation operating system. Previous sound file formats, in order to reduce the size, used the logarithmic scale of recording samples. Among the representatives of such formats, the Sun AU group of formats, which are still in action, gained great fame. Problems with opening the AU file usually manifest themselves when there are no corresponding applications that would be installed on the PC. Applications that use .AU files are Apple QuickTime Player, Microsoft Windows Media Player, Real Player, Winamp, and other widely used audio players. And this is the vast majority of professional audio editors.