Discord is encoding and streaming in realtime on top of a bunch of noise gating filters. Opus is the most efficient audio codec we've got. (For stereo anyway.)

Discord is encoding and streaming in realtime on top of a bunch of noise gating filters. Opus is the most efficient audio codec we've got. (For stereo anyway.) At high bitrates there might be better tuned ones, but also at high bitrates it doesn't really matter what you use as long as it's not MP3.