Currently, an estimated 5% of data packets sent over the Internet are lost. In a videoconferencing session, packet loss causes video frame freeze, error propagation, and audio glitches. For this reason, QoS (Quality of Service) and packet-loss robustness features are very important for videoconferences conducted over "best-effort" IP networks.
The main objective of QoS features used in conventional videoconferencing endpoints is to "conceal" the error. For example, certain technology is used to shuffle image data for transmission so that packet loss does not destroy wide areas of the video image. Other technology is used to increase "intra" macroblocks that do not require previous frame information. This prevents the packet loss error from propagating over a long period, but results in a lower frame rate as the increased amount of intra macroblocks requires more bits to carry the video frames. Sony has developed new QoS features using a different approach: "recovering" the error rather than "concealing" it, and thereby maintaining the quality of realtime communication.
