KAR is the original format of audio files for creating karaoke, which are formed in a variety of software systems. It has the ability to save not only MIDI file data, but also lyrics. The KAR format is part of the .midi extension. In most cases, they are used as a source for adding special text to regular MIDI files, and they also differ from the Karaoke file. After all, there is no additional track with words that are synchronized with the main melody according to certain algorithms. As a rule, in order to realize the vocal part, you must apply the first track. For a stream of words, a second track is used. This file extension can be obtained using specialized software. But not only. It can also be created using MIDI keyboards that are connected to computer hardware. If there are appropriate plugins, then you can open the KAR file using the Media Player traditional for the Windows operating system. Anyone using the Mac OS platform can play KAR files in the Mireth Technology Music Man karaoke application. But the universal option for this pair of systems is PG Music Band-in-a-Box. This software is the most popular among analogues. Together with the .KAR extension, they sometimes provide reference data on where audio catalogs and item metadata associated with audio tracks are located. It is also possible that there is information about the artist and about the albums.
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.