EVS Standard

  • The new codec for Enhanced Voice Services (“EVS”), successor to the current mobile HD voice codec AMR-WB, was standardized by the 3rd Generation Partnership Project (“3GPP”) in September 2014. The EVS codec employs cutting-edge technology to significantly enhance the communication quality, efficiency and versatility of 3GPP mobile communication systems.

  • The EVS codec was developed through collaboration among several leading companies in the industry including chipset, handset and infrastructure manufacturers, operators, and technology providers. The standardization followed the rigorous 3GPP process of setting aggressive requirements and design constraints, verified through the qualification, selection, and characterization phases with extensive subjective testing performed by world-class independent test labs.

  • Key applications for enhanced voice services include:
    • Improved classical telco-grade telephony, and high-quality multi-party conferencing and audio-visual communications, offering a ‘being-there’ quality of experience.
    • Delivery of high-performance streaming and offline voice and audio are also enabled by the EVS codec.

Advantages and Features of the EVS Codec

Mobile Telephony

  • EVS is especially designed for Voice over LTE (“VoLTE”) services.

Full-HD Voice Audio Quality

  • EVS delivers unprecedented quality for speech, background music and mixed content,
    and outperforms AMR-WB at all operational points.

  • EVS enables discontinuous transmission (“DTX”) with algorithms for voice/sound activity detection (“VAD”)
    and comfort noise generation (“CNG”).

Higher Efficiency and Versatility

  • EVS offers Variable Bit Rate (“VBR”) across a wide range of bit rates from 5.9 kbit/s to 128 kbit/s, allowing service providers to optimize network capacity and call quality as desired for their service.

  • EVS improves the compression efficiency at all operational rates.

  • EVS is capable of switching bit rates at every 20-ms frame allowing the codec to easily adapt to changes in channel capacity.

Increased Reliability

  • EVS utilizes unique concealment techniques to minimize the impact of packet loss caused by
    adverse conditions in the transmission channel.

  • EVS includes a system for Jitter Buffer Management (“JBM”).

Backward Compatibility With Existing VoLTE Services

  • The codec’s integrated AMR-WB interoperability mode eliminates the need for a separate AMR-WB implementation allowing the signal to quickly switch between VoLTE (4G) and circuit switched networks (3G).

Comparison of Codec Standards

EVS Technology Characteristics

Standardized 3GPP 2014
Sampling rates 8, 16, 32 and 48 kHz
Modes & Encoded Bandwidth NB (20-4000 Hz)
WB (20-8000 Hz)
SWB (20-16000 Hz)
FB (20-20000 Hz)
Modes & Encoded Bandwidth ACELP/MDCT (content-driven switching between speech and audio compression)
Improved ACELP extended with specialized modes for different speech content
MDCT-based coding in different variants for audio coding
Efficient MDCT coding at low delay/low bitrates
Seamless and reliable switching between the speech and the audio cores
Bandwidth extensions optimized for diverse content
Bit rate (kbps) NB: 7.2, 8, 9.6, 13.2, 16.4, 24.4
WB: 7.2, 8, 9.6, 13.2, 16.4, 24.4, 32, 48, 64, 96, 128
SWB: 9.6, 13.2, 16.4, 24.4, 32, 48, 64, 96, 128
FB: 16.4, 24.4, 32, 48, 64, 96, 128

NB & WB VBR: ~5.9 kbps

AMR WB Interoperable Mode:
6.6, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05, 23.85
Frame size

20 ms
12 ms (extra encoder and decoder delay)
Quality NB: Improved quality and packet loss robustness over AMR-NB
WB: Improved quality and packet loss robustness over AMR-WB
SWB: Unprecedented SWB quality at mobile bit rates (starting at 9.6 kbps)
Mixed content and music: Significantly improved quality over AMR-WB
Jitter Buffer Management Included
VAD/DTX/CNG Included

EVS Specifications

3GPP TS 26.441 General Overview
3GPP TS 26.442 ANSI C code (fixed-point)
3GPP TS 26.443 ANSI C code (floating point)
3GPP TS 26.444 Test Sequences
3GPP TS 26.445 Detailed Algorithmic Description
3GPP TS 26.446 AMR-WB Backward Compatible Functions
3GPP TS 26.447 Error Concealment of Lost Packets
3GPP TS 26.448 Jitter Buffer Management
3GPP TS 26.449 Comfort Noise Generation (CNG) Aspects
3GPP TS 26.450 Discontinuous Transmission (DTX)
3GPP TS 26.451 Voice Activity Detection (VAD)

Technical Report

3GPP TR 26.952: EVS Codec Performance characterization
The TR provides information on the EVS codec Selection, Verification and Characterization Phases

Service-Related Specifications

EVS RTP Payload Format: Specified in Annex A of 3GPP TS 26.445.
Media Type Parameters descriptions and handlings: specified in this Annex A of 3GPP TS 26.445 and in 3GPP TS 26.114 (which also specifies other guidelines and operations necessary for the handling of the EVS codec such as QoS handling, codec control, and interworking with other networks)