discord

Discord is a widely used voice + text chat application. It's omnipresent in modern online communities.

Their voice chat makes use of [opus] for encoding/decoding. This is evident since they don't seem to be stripping their binaries, at least not on Linux. Using perf on the Discord process, it's possible to see several opus functions in the trace:

Some of them, such as opus_fft_impl, are used in other projects that use Opus code. The one I know I've seen it in before is [rnnoise], see the code directly: .

I get a kick out of the fact that the license for some of that Opus code that was compiled into Discord is licensed "Copyright (c) 2006-2011, Skype Limited": https://github.com/xiph/opus/blob/7b05f44f4baadf34d8d1073f4ff69f1806d5cdb4/silk/NLSF_del_dec_quant.c#L2