3G2 is an audio / video format that was developed using the 3rd Generation Partnership Project 2 (3GPP2). The file extension is an improved version of the 3GP format. Today it is already outdated, despite the fact that it was previously updated. As a result of the implementation of the 3rd Generation Partnership Project, standards were developed that relate to methods of transmitting a wide variety of media data. For example, on mobile networks. The development of such standards, in particular, has led to the introduction of the 3G2 format and to the use of various types of media data on the global network for online streaming. This type of file is most often used on mobile phones, as well as on phones that support 3G. 3G2 video files can also be played on many computers. We emphasize that in this case there may be a need for additional applications. The 3G2 format is very similar to the MPEG-4 Part 14 series (MP4) format. However, in comparison with it, the 3G2 format is not so complicated. When you apply this type of file, you need to consider the possibility of reducing the requirements for the width of both the information transfer channel and disk space. So, the format for mobile phones is exactly what you need. 3G2 files have been specifically developed for phones operating in the CDMA standard.
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.