IETF RFC 4788 PDF

This document updates the Enhanced Variable Rate Codec (EVRC) RTP payload formats defined in RFC 3558 with several enhancements and extensions. In particular, it defines support for the header-free and interleaved/bundled packet formats for the EVRC-B codec, a new compact bundled format for the EVRC and EVRC-B codecs, as well as discontinuous transmission (DTX) support for EVRC and EVRC-B-encoded speech transported via RTP. Voice over IP (VoIP) applications operating over low bandwidth dial-up and wireless networks require such enhancements for efficient use of the bandwidth.