MP3 is the most common music (sound) file format. This format was developed by Fraunhofer IIS and Thomson. This format for storing and transmitting music (sound) files in digital form uses signal compression technology. That is why, unlike the previously widespread WAV format, MP3 files (full name - MPEG Audio Layer-3) are much smaller in size, and their sound quality is much higher. The MP3 format was one of the first and most successful sound compression methods. One of the important characteristics of this process is the degree of compression, that is, how much data is transferred per unit of time. Standard MP3 encoding is from 64 to 320 kb / s.
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.