Following my earlier post on "Opus SDP negotiation" in the series "For The Practical Man", I'm presenting today a related topic: Opus audio codec when transcoding is involved. Most of the providers of PSTN connectivity require the simplest possible VoIP codec: G.711 (which comes in two flavours, u-law and a-law). G.711 is a sort of PCM encoding at 8000 samples per second: 8000 times per second an audio sample is encoded with 8 bit. Sometimes Comfort Noise can be used, reducing the bitrate when silence is detected, but otherwise the typical working principle is a continuous flow of digitally-encoded packets of voice. u-law and a-law just use a different way to encode the data. (If you're curious about what does silence look like in G.711, I wrote a post about it some time ago ). G.729 is another widely adopted codec, but I'll leave it for another day. With 8000 samples per second and 8 bit dedicated for each sample G.711 requires a net...