MPC is one of the files of the Audio category. This unlicensed file format is intended to store audio information. The MPC format (i.e. Musepack Compressed Audio File) was created by Musepack. Musepack is a lossy compression scheme developed by German programmer Andree Buschmann. He started creating the codec in 1997. At that time he had the name MP +. The developer was not satisfied with the existing quality of MP3 coding. The algorithm is based on MP2 (MPEG-1 Layer 2), where there are 32 frequency bands, but with significant improvements. Over the past years, it has undergone revision and has become much better. It is currently at a more advanced stage, which contains highly optimized and unpatented source code. The MPC encoding quality at high bitrates (160 Kbps and more) is much higher than the quality that MP3 provides. During coding, a different psychoacoustic compression algorithm is used. In MPC, frequencies that ignore MP3 encoders do not disappear. The specificity of MPC is the fine tuning of psychoacoustics. This provides the ability to operate with pure VBR encoding (variable bit rate encoding). The main task of Musepack is to obtain the highest transparency of sound.
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.