RM is a video file format developed by RealNetworks. It uses the RealPlayer player, that is, a program for streaming audio and video files. The format contains audio and video data or links to streaming, which can be played back as it downloads. The RealMedia Player program was in great demand when they connected to the Internet using a modem, and when there was practically no broadband access to the global network. The large compression ratio of the format provided the opportunity to carry out online transmission of video and audio data. The quality of the output file, as a rule, was low. Today, such files are often used in order to broadcast Internet radio and Internet video. In the .RM format, music and video are found on the global network or on Western cable channels, on Internet radio stations. Support for this format is carried out by such mobile phones and smartphones as Nokia, Ericsson, Sony, iPhone, as well as mobile devices that operate on the Google Android operating system. Files with the extension .RM are compressed using proprietary codecs RealVideo and RealAudio. Individual Real Media files can be played using a VLC media player that partially supports RM files.
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.