Today's Internet is increasingly used not only for e-mail, ftp and WWW, but for interactive audio and video services. However, the Internet as a datagram network offers only a ``best effort'' service, which can lead to excessive packet losses under congestion. Internet measurements have shown that the overall probability to loose one packet is high, however drops significantly for the loss of several consecutive packets.

With the "Adaptive Packetization / Concealment" scheme this Internet loss characteristic and the property of long-term correlation within a speech signal is considered together, to mitigate the impact of packet losses. This is accomplished by an adaptive choice of the packetization interval of the voice stream at the sender. When a packet is lost, the receiver can use adjacent signal segments to conceal the loss to the user, because a high similarity can be assumed due to the adaptive packetization at the sender. AP/C thus enhances the subjective quality of voice streams over packet-switched networks and is applicable within the current Internet environment (high loss rates, common audio tools, standard speech codecs).