| Enhanced Voice Services (EVS) | |
|---|---|
| Internet media type | audio/EVS |
| Developed by | Fraunhofer,JVCKenwood,Nippon Telegraph and Telephone,NTT Docomo,Panasonic,Ericsson |
| Type of format | Lossyaudio |
| Standard | 3GPP TS 26.441, 26.442 |
Enhanced Voice Services (EVS) is asuperwidebandspeechaudio coding standard that was developed forVoLTE andVoNR. It offers up to 20 kHz audio bandwidth and has high robustness to delay jitter and packet losses due to its channel aware coding[1] and improvedpacket loss concealment.[2] It has been developed in3GPP and is described in3GPP 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 as3GPP 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.[3] The codec was developed collaboratively among chipset, handset and infrastructure manufacturers as well as operators and technology providers.[4]
GSMA requires EVS for their HD Voice+ Logo Licensing Program.[5]
The six patent holders areFraunhofer IIS,JVC Kenwood,Nippon Telegraph and Telephone,NTT Docomo,Panasonic, andEricsson.[6] Other contributors includedHuawei,Nokia,Orange,Qualcomm,Samsung Electronics, VoiceAge, andZTE Corporation.[4] Apatent pool for EVS and IVAS has been listed byVia-LA.[7]
EVS employs similar concepts to its predecessors, such asAMR-WB, to which it retains backward-compatibility. It switches between speech and audio compression modes depending on the content, usingACELP andMDCT.
The following features are present in EVS:[8]
Input sampling rates for EVS can be 8, 16, 32, and 48 kHz. It supports the following bitrates (in kbps) for different bandwidths:[8]
Bitrates can be switched every 20 ms.[3]
Subjective listening tests conducted by Nokia concluded that EVS offers significantly improved quality overAMR andAMR-WB at all operating points.[3]
Operators which have launched EVS poweredVoLTE services include:[9][failed verification]
As of 2024 there are about 200 models from different smartphones manufacturers supporting EVS, including:[9]
Inter-carrier interoperability is a problem, as calls are by default routed over narrowband connections which downgrades the voice to narrowband quality instead of EVS andHD Voice even if the individual phones and carrier networks all support EVS. However, this does not mean it gets disabled though, the call remains on VoLTE or VoNR.[11] Thus, users are encouraged to switch from phone calls to pure VoIP apps such asFaceTime,WhatsApp,Signal,Facebook Messenger, andTelegram when voice call quality remains poor despite good network connectivity.[12] Still in some cases interoperator connection is implemented and phone call remains in EVS.
EVS, like AMR-WB and AMR-WB+, incorporates severalpatents. As with those two codecs, VoiceAge Corporation is in charge of the licensing[13] and offers RAND pricing[14]