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.
M4R is a highly specialized audio file format. This format (full name - iPhone Ringtone File) was developed by Apple's IT giant specifically for the iPhone. This format creates music ringtones for the iPhone. ITunes Ringtone is the main program for opening files with the extension .m4r, and their creation is mainly using Apple iTunes. Formally, M4R files can only be created from songs and other works purchased in the iTunes music store. The size of the created ringtone in the M4R format can be a maximum length of not more than 40 seconds.