Description

64 kbit/sec A/u-law voice codec fully compliant with ITU-T G.711 recommendation. Packet loss concealment (PLC) feature enables it for use in a wide range of internet/mobile applications such as VoIP and videoconferencing products. The objective of PLC is to generate a synthetic speech signal to cover missing data (erasures) in a received bit stream. It tries to synthesize the signal that has the same timbre and spectral characteristics as the missing signal. If the erasures are not too long, and the erasure does not land in a region where the signal is rapidly changing, the erasures may be inaudible after concealment. VAD/CNG feature provides means to use of discontinuous transmission in a packet-based communication system that can significantly reduce the transmission rate and hence improve the bandwidth efficiency. It uses generic payload format and may also be used with other speech codecs without built-in DTX capability such as G.726, G.727, G.728, and G.722. The VAD algorithm makes a voice activity decision based on multiple parameters such as the full band energy, the low band energy, the zero-crossing rate and a spectral measure. This provides robust decision over a wide range of conditions and the level of ambient noise.