SYSTEM FOR LOST PACKET RECOVERY IN VOICE OVER INTERNET PROTOCOL BASED ON TIME DOMAIN INTERPOLATION

摘要

A lost packet recovery device, method and computer program for use in a VoIP system in which lost packets containing voice information are replaced using time domain interpolation techniques. These time domain interpolation techniques employ two different approaches to interpolate missing data packets. The first approach relies on time domain harmonic scaling to interpolate a replacement frame for a missing frame using the frames that come before and after the missing frame. The second approach replicates a frame immediately prior to the missing frame. This replicated frame then has an energy reduction function applied to it to gradually reduce the energy output level of the data samples in the frame. This replicated frame is then used to replace the missing frame. In the second approach, the process of duplicating the prior frame and reducing its energy levels using an energy reduction function is repeated until no further missing frames are detected. Once no further missing frames are detected, an energy restoration function is applied to the next available frame to gradually increase its energy level and provide for a smooth transition. Using these techniques, missing frames of voice data may be replaced to mask the effects of missing frames to a listener.