Enhanced Voice Services

Enhanced Voice Services (EVS)
Internet media type	audio/EVS
Developed by	Fraunhofer, JVCKenwood, 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 and VoNR. 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 improved packet loss concealment.^[2] 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.

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.^[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 are Fraunhofer IIS, JVC Kenwood, Nippon Telegraph and Telephone, NTT Docomo, Panasonic, and Ericsson.^[6] Other contributors included Huawei, Nokia, Orange, Qualcomm, Samsung Electronics, VoiceAge, and ZTE Corporation.^[4] A patent pool for EVS has been listed by MPEG LA.^[7]

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:^[8]

source-controlled variable bit-rate (SC-VBR)
voice/sound activity detector (VAD)
comfort noise generation (CNG)
error concealment (EC) for packet loss in networks
channel-aware mode to improve frame/packet error resilience
jitter buffer management (JBM)

Input sampling rates for EVS can be 8, 16, 32, and 48 kHz. It supports the following bitrates (in kbps) for different bandwidths:^[8]

Narrowband (NB): 5.9, 7.2, 8, 9.6, 13.2, 16.4, 24.4
Wideband (WB): 5.9, 7.2, 8, 9.6, 13.2, 13.2 channel-aware, 16.4, 24.4, 32, 48, 64, 96, 128 (6.6 ~ 23.85 for AMR-WB IO)
Super-wideband (SWB): 9.6, 13.2, 13.2 channel-aware, 16.4, 24.4, 32, 48, 64, 96, 128
Fullband (FB): 16.4, 24.4, 32, 48, 64, 96, 128

Bitrates can be switched every 20 ms.^[3]

Subjective listening tests conducted by Nokia concluded that EVS offers significantly improved quality over AMR and AMR-WB at all operating points.^[3]

Adoption

Operators which have launched EVS powered VoLTE services include:^[9]^{[failed verification]}

As of 2024 there are about 200 models from different smartphones manufacturers supporting EVS, including:^[9]

Interoperability

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 and HD Voice even if the individual phones and carrier networks all support EVS.^[11] Thus, users are encouraged to switch from phone calls to pure VoIP apps such as FaceTime, WhatsApp, Signal, Facebook Messenger, and Telegram when voice call quality remains poor despite good network connectivity.^[12]

Licensing

EVS, like AMR-WB and AMR-WB+, incorporates several patents. As with those two codecs, VoiceAge Corporation is in charge of the licensing^[13] and offers RAND pricing^[14]

References

^ Atti, V.; Sinder, D. J.; Subasingha, S.; Rajendran, V.; Dewasurendra, D.; Chebiyyam, V.; Varga, I.; Krishnan, V.; Schubert, B. (2015-04-01). "Improved error resilience for volte and VoIP with 3GPP EVS channel aware coding". 2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). pp. 5713–5717. doi:10.1109/ICASSP.2015.7179066. ISBN 978-1-4673-6997-8. S2CID 17443373.
^ Lecomte, J.; Vaillancourt, T.; Bruhn, S.; Sung, H.; Peng, K.; Kikuiri, K.; Wang, B.; Subasingha, S.; Faure, J. (2015-04-01). "Packet-loss concealment technology advances in EVS". 2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). pp. 5708–5712. doi:10.1109/ICASSP.2015.7179065. ISBN 978-1-4673-6997-8. S2CID 11693594.
^ ^a ^b ^c The 3GPP Enhanced Voice Services (EVS) codec. Nokia white paper.
^ ^a ^b Enhanced Voice Services (EVS) Codec. Fraunhofer Technical Paper, 2015
^ "HD Voice". Future Networks. Retrieved 2020-05-10.
^ "Licensors Included in the EVS Patent Portfolio License". MPEG LA. Retrieved 10 July 2019.
^ MPEG LA Facilitating Development of Enhanced Voice Services Patent Pool License Archived 2016-03-09 at the Wayback Machine. MPEG LA News Release, 20.01.2016
^ ^a ^b Järvinen, Kari. "Enhanced Voice Services Codec for LTE". 3GPP.
^ ^a ^b "EVS". Fraunhofer Institute for Integrated Circuits IIS. Retrieved 2020-05-10.
^ https://www.howardforums.com/threads/att-evs.1918271/ ^{[bare URL]}
^ Segan, Sascha (April 2018). "How to Make Your Cell Phone Calls Sound Better". PCMAG.
^ "What to Do If Your Smartphone's Voice Call Quality Sucks". Lifehacker. 13 April 2018. Retrieved 29 December 2022.
^ "VoiceAge EVS". voiceageevs.com.
^ "RAND pricing". voiceageevs.com.