Bitrate only tells a little bit of the story. There are high pass and low pass filters, audio compression, data compression, latency, error correction and a num

Bitrate only tells a little bit of the story. There are high pass and low pass filters, audio compression, data compression, latency, error correction and a number of other things at play with these codecs to hit a desired bitrate with the goal of maximizing for highest legibility over unreliable connections. This leads to a number of compromises; in the case of Skype this means you can have huge variance in quality, and landlines are consistent but incredibly limited in reproducible bandwidth and dynamic range.