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Enhanced Voice Services Codec for LTE

By Kari Järvinen, Chairman, TSG SA WG4

3GPP SA4 has completed work on the Enhanced Voice Services (EVS) Codec, in Release 12, to enable vastly improved voice quality, network capacity and advanced features for voice services over LTE and other radio access technologies standardized by 3GPP. 

EVS is the first 3GPP conversational codec offering up to 20 kHz audio bandwidth, delivering speech quality that matches other audio input such as stored music, while offering high robustness to delay jitter and packet losses.

Designed to meet the demands of packet-switched mobile communications networks, the EVS codec has been developed and standardized under the lead of the 3GPP Codec Working Group, 3GPP TSG SA WG4.

EVS image2The new codec includes a multi-rate audio codec, a source controlled variable bit-rate (SC-VBR) scheme, a voice/sound activity detector (VAD), a comfort noise generation (CNG) system, and an error concealment (EC) mechanism to neutralize the detrimental effects of transmission errors resulting in lost packets. The codec also features a channel-aware mode which further improves frame/packet error resilience. To reduce the impact of variable transmission time - A jitter buffer management (JBM) is also provided.

For narrowband and wideband audio bandwidths, the EVS codec delivers higher quality, higher frame/packet error resilience, and higher compression efficiency than previous speech codecs, leading to improved user experience and system efficiency. Further quality enhancement is provided through the introduction of super-wideband and fullband audio bandwidths. The EVS codec also provides enhanced interoperation with the AMR-WB codec over all nine operational bit-rates. When the EVS codec is supported, the EVS AMR-WB Inter-Operable mode may serve as an alternative implementation of AMR-WB codec.

With a host of novel features designed to enhance operation in harsh operating environments, and advanced compression techniques that apply tailored algorithms to cover a wide range of inputs, the EVS codec, along with a tight integration with LTE and the next-generation mobile communications systems, will deliver unrivaled quality and capacity compared to any current multimedia telephony system while opening up opportunities for new services and devices.

The EVS codec supports operating points as shown in the following table:

Bandwidth

Bit Rate (kbps)

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

New and updated Technical Specifications bringing support for EVS into 3GPP are:

Spec

Title

3GPP TS 26.441

"Codec for Enhanced Voice Services (EVS); General Overview".

3GPP TS 26.442

"Codec for Enhanced Voice Services (EVS); ANSI C code (fixed-point)".

3GPP TS 26.443(*)

"Codec for Enhanced Voice Services (EVS); ANSI C code (floating point)".

3GPP TS 26.444

"Codec for Enhanced Voice Services (EVS); Test Sequences".

3GPP TS 26.445

"Codec for Enhanced Voice Services (EVS); Detailed Algorithmic Description".

3GPP TS 26.446

"Codec for Enhanced Voice Services (EVS); AMR-WB Backward Compatible Functions".

3GPP TS 26.447

"Codec for Enhanced Voice Services (EVS); Error Concealment of Lost Packets".

3GPP TS 26.448

"Codec for Enhanced Voice Services (EVS); Jitter Buffer Management".

3GPP TS 26.449

"Codec for Enhanced Voice Services (EVS); Comfort Noise Generation (CNG) Aspects".

3GPP TS 26.450

"Codec for Enhanced Voice Services (EVS); Discontinuous Transmission (DTX)".

3GPP TS 26.451

"Codec for Enhanced Voice Services (EVS); Voice Activity Detection (VAD)".

3GPP TS 26.114(*)

"IP Multimedia Subsystem (IMS); Multimedia telephony; Media handling and interaction".

 (*) To be updated to include EVS by Dec 2014 after SA#66 meeting approval

Detailed information on the performance of EVS codec will be available in the following Technical Report: 

3GPP TR 26.952

"Codec for Enhanced Voice Services (EVS); Performance Characterization".

The CODEC Specifications and Reports in the 26 Series are available here: http://www.3gpp.org/DynaReport/26-series.htm

3GPP Contacts on this topic:

This email address is being protected from spambots. You need JavaScript enabled to view it. – EVS SWG Chairman
This email address is being protected from spambots. You need JavaScript enabled to view it. – TSG SA4 WG Chairman

 

 

 

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