Enhanced Voice Services (EVS) is a superwidebandspeechaudio coding standard that was developed for VoLTE. It offers up to 20 kHz audio bandwidth and has high robustness to delay jitter and packet losses due to its channel aware coding and improved packet loss concealment. It has been developed in 3GPP and is described in 3GPP TS 26.441. The application areas of EVS consist of improved telephony and teleconferencing, audiovisual conferencing services, and streaming audio. Source code of both decoder and encoder in ANSI C is available as 3GPP TS 26.442 and is being updated regularly. Samsung uses the term HD+ when doing a call using EVS.
Work on EVS was started in 2007. The standardization process lasted from 2010 to 2014, being completed in December 2014 with 3GPP Release 12. The codec was developed collaboratively among chipset, handset and infrastructure manufacturers as well as operators and technology providers.
GSMA requires EVS for their HD Voice+ Logo Licensing Program.
EVS employs similar concepts to its predecessors, such as AMR-WB, to which it retains backward-compatibility. It switches between speech and audio compression modes depending on the content, using ACELP and MDCT.
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^ abcThe 3GPP Enhanced Voice Services (EVS) codec. Nokia white paper.