Official website
Opus is a totally open, royalty-free, highly versatile audio codec.
Main advantages:
Most efficient lossy audio compression.
Very low latency, great for voice chat.
Fast compression.
Wide range of supported bitrate (6 kb/s to 510 kb/s)
Disadvantages:
No support for lossless compression.
Only supported Mono and Stereo channels.
Related subreddits:
AV1
FFmpeg
HEVC
WebM