Better Voice Quality Using Wideband Codecs
The initial VoIP implementations tried to meet the standards set by the legacy PSTN. Legacy PSTN switches and PBX have a limited bandwidth of 4 kHz, which allows sampling of audio frequencies between 300 Hz3400 Hz. While the PSTN is restricted to narrowband frequencies, VoIP permits the use of wideband codecs. Wideband codecs sample at 16 kHz, allowing transmission of frequencies up to 8 kHz. These codecs offer much better sound clarity without a high demand on network bandwidth.
G722.2 is a wideband codec defined by ITU. G722.2 is an adaptive multirate codec with a bit rate between 6 and 23.85 kbps. iSAC from Global IP Sound is another wideband codec with a variable transmission rate between 10 and 32 kbps. iSAC is also robust against packet loss. Both of these codecs sample at 16 kHz.
These codecs are useful for VoIP applications such as distance learning, on-demand training, conferencing, and multimedia sessions such as online gaming. These codecs help improve the user experience by providing more realistic sound quality.