What is a OPUS file?
Modern audio codec optimized for voice and streaming
The OPUS file is an audio file format that was created for use in Voice over IP (VoIP), video conferencing, or in-game chat. Since the OPUS codec is primarily used in Internet streaming applications, it isn't common. However, is it a lossy audio format that uses both SILK (used by Skype) and CELT (from Xiph.Org) codecs and supports variable bit rates from 6 kb/s to 510 kb/s.