OPUS is an audio file that is encoded using the Ogg Opus format (lossy coding). It was created for online audio streaming, that is, in order to transmit sound through a global network. The format is being developed by the Internet Engineering Task Force (IETF) and Xiph.Org communities. Applies SILK codecs when used in Skype and CELT (from Xiph.Org), provides support for variable bitrate. Most often, the OPUS codec is used for video conferencing, game chats, VoIP telephony. OPUS is a free audio codec that has international standard status (IETF RFC 6716). Its main advantages are a low coding delay (from 2.5 to 60 ms) and its significant speed, an increased degree of compression of audio data with high-quality sound, as well as support for multi-channel audio (within 255 channels). In 2011, J. Skeglund of Google conducted two series of tests, during which OPUS coding and decoding were compared, taking into account the assessments of experts and ordinary listeners. Studies have shown that OPUS provides stereo music with the same quality as MP3 and better quality than G.719 64 kbps. OPUS offers great streaming capabilities with dynamic tweaking and very low latency. This is always high sound quality and excellent data compression. Full support for OPUS is provided by Mozilla applications. He is the key Skype audio codec.
RA is a streaming audio file category format designed to play audio over a wide area network. The RA (RealAudio) file format was developed by RealNetworks in the mid-90s of the last century. The file itself contains encoded audio information, but it may also contain links to audio content. It may contain audio data or reference an audio streaming file. In order to compress the data, they use their own Real compression algorithm with a variable bitrate, as well as a variety of codecs. The .ra file format is a common format required to play streaming audio on the Internet. Real Audio is a standard format for playing audio clips in a web browser. As a rule, they use the RealOne Player to play it. However, due to the fact that it is completely unsuitable and clogged with advertising, they recommend the RealAlternative package. Previously, most radio stations broadcasting online used this particular format. Also until 2009, the format was used on its website by BBC. Currently, the RA format is not so popular among those who broadcast online, since new technologies have already been introduced.