Opus is a lossy audio coding format developed by the Xiph.Org Foundation and standardized by the Internet Engineering Task Force, designed to efficiently code speech and general audio in a single format, while remaining low-latency enough for real-time interactive communication and low-complexity enough for low-end ARM3 processors. Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.
SND is a file extension for a sound file used with a variety of platforms. SND stands for SouND. SND files may contain audio data specific to a Macintosh sound resource (from Mac OS Classic), an AKAI MPC audio sample, a generic Amiga sound, or other audio file. SND files can often be opened by Apple’s Quicktime Player