The FreeSWITCH implementation of the CELT codec allows any other device that can use CELT to send ultra-high-definition audio in a very small package. The bandwidth rate of 48kps in the FreeSWITCH implementation is actually less data per stream than the audio format that traditional telephones use.
Higher frequencies allow more detail in the audio making things like music and voice sound more rich and true to it's original sound. This offers a new frontier for telephony. The world has grown used to the low quality of the PSTN but many would happily exchange it for crystal clear call-quality to go with this new High-Definition age.
CELT stands for "Constrained Energy Lapped Transform" and is created by the same team responsible for the Speex codec.
FreeSWITCH is an Open Source soft-switch and application server hosted at http://www.freeswitch.org"