Enhanced Voice Services


Enhanced Voice Services 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 . The application areas of EVS consist of improved telephony and teleconferencing, audiovisual conferencing services, and streaming audio.

History

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 and 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.

Technology

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 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.

Adoption

Operators which have launched EVS powered VoLTE services include:
Currently there are about 200 models from different smartphones manufacturers supporting EVS, including: