VOB is a DVD-based multimedia container video file format developed by the DVD Forum. It is based on MPEG-2. A file with the .VOB extension can have video and audio streams, audio and video data, subtitles, disc menus, and navigation content. And all this is combined into a common stream. In this case, video playback is carried out in MPEG-2 format, and audio in various audio formats. Most often, the AC-3 format is used for this, since it provides the most favorable ratio of bitrate and sound quality. The VOB format has gained popularity as files in which you can store video and sound on DVD discs. As a rule, if they have such an extension, then the files have a place in the VIDEO_TS DVD folder in the DVD root directory. Typically, .VOB format videos are opened using any video player that supports MPEG-2 compression. There are many free players that support the .VOB format. In particular, Zoom Player, Media Player Classic VLC, Media Player, Light Alloy and others. Now popular is the paid player CyberLink PowerDVD, which has rich functionality. He specializes in playing DVD videos. VOB video files, originally called DVD Video Object File, can be accompanied by .IFO and .BUP information files.
3GA is a 3GPP audio file created in 1998. It was created by the 3rd Generation Partnership Project. It is used mainly on mobile devices in order to record, play and transmit audio data. 3GPP (3rd Generation Partnership Project) is a consortium that develops specifications for mobile telephony. The format resembles 3GP files, however, it includes only audio data. In most cases, 3GA files are used by mobile phones in order to record and transmit audio data. For example, this is how audio is recorded in Samsung Galaxy phones. The .3GA file extension can be changed to .3GP, which is widespread. Everything is supported by many programs. The 3GA format uses an adaptive coding audio codec with variable speed (AMR, AMR-NB, GSM-AMR). The development of this codec was done in order to compress encoded speech signals using adaptive modulation. In 1999, the 3GPP consortium adopted the Adaptive Variable Rate Coding (AMR) standard. Currently, it is used by GSM and UMTS communication systems. It is this format for speech recording that has found wide application on mobile devices. We note at the same time that it is not possible to play such files very often on certain devices.