Audio transmission over the Internet: experiments and observations

The performance of IP telephony systems is highly dependent on the audio codecs and their reaction to packet loss and instantaneous delays. Understanding the interaction between audio encoding and the dynamic behavior of the Internet is significant for designing adaptive audio transport mechanisms. For this purpose, we conducted a large-scale audio transmission experiment over the Internet in a 12-month period using various Internet sites. As a result of this experiment, we have made a number of new observations to assess the audio quality of G.711 and G.728 codes under different loss and delay conditions. The paper also states a number of recommendations for implementing efficient adaptive FEC and playout mechanisms.