|Internet media type||audio/EVS|
|Developed by||Fraunhofer, JVC Kenwood, Nippon Telegraph and Telephone, NTT Docomo, Panasonic, Ericsson|
|Type of format||Lossy audio|
|Standard||3GPP TS 26.441, 26.442|
Enhanced Voice Services (EVS) is a superwideband speech audio 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.
The six patent holders are Fraunhofer IIS, JVC Kenwood, Nippon Telegraph and Telephone, NTT Docomo, Panasonic, and Ericsson. Other contributors included Huawei, Nokia, Orange, Qualcomm, Samsung Electronics, VoiceAge, and ZTE Corporation. A patent pool for EVS has been listed by MPEG LA.
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.
The following features are present in EVS:
Input sampling rates for EVS can be 8, 16, 32, and 48 kHz. It supports the following bitrates (in kbps) for different bandwidths:
Bitrates can be switched every 20 ms.
Subjective listening tests conducted by Nokia concluded that EVS offers significantly improved quality over AMR and AMR-WB at all operating points.
Operators which have launched EVS powered VoLTE services include:
Currently there are about 200 models from different smartphones manufacturers supporting EVS, including:
EVS, like AMR-WB and AMR-WB+, incorporates several patents. As with those two codecs, VoiceAge Corporation is in charge of the licensing.