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AMR-WB, Adaptive Multi-Rate - Wideband Speech Codec

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name AMR-WB, Adaptive Multi-Rate - Wideband Speech Codec (G.722.2)
Description

Audio data compression scheme optimized for speech coding in GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System), an elaboration of AMR, and featuring Algebraic Code Excited Linear Prediction (ACELP) compression coding.

The AMR-WB bitrates are 6.60, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05 and 23.85 kbps. Compared to narrowband speech codecs (like AMR) optimized for traditional telephone voice quality of 300-3400 Hz, the AMR-WB codec's wider bandwidth of 50-7000 Hz provides excellent speech quality.

Although AMR-WB pre-dates AMR-WB+, it is more constrained and is therefore treated as a subtype of AMR-WB+ at this Web site; Comments welcome.

Production phase Final-state for end-user delivery.
Relationship to other formats
    Subtype of AMR-WB+, Extended Adaptive Multi-Rate - Wideband Speech Codec. . Comments welcome.

Local use Explanation of format description terms

LC experience or existing holdings AMR-WB+ has been selected as the audio codec for LC-produced Digital Talking Books; see also DTB.
LC preference None

Sustainability factors Explanation of format description terms

Disclosure

Open standard. Developed by 3GPP, a collaboration of telecommunications industry and standards groups in Europe, Asia, and North America. The key European organization is ETSI (European Telecommunications Standards Institute).

AMR-WB is also codified by ITU-T (International Telecommunication Union-Telecommunication Standardization Sector).

    Documentation

3GPP TS 26.171 v.6.0.0 (2004-12), Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); AMR speech codec, wideband; General Description, and other specifications listed in Format specifications below. Some of the other specifications carry different version numbers; it is not clear to the compiler of this Web page if AMR-WB in and of itself has a version number; Comments welcome. The 3GPP Web site lists versions of this documents dating to 2001.

AMR-WB is also specified as ITU-T G.722.2, Wideband coding of speech at around 16 kbit/s using Adaptive Multi-Rate Wideband (AMR-WB). The earliest of the group of specifications under this number is dated 2002; the ITU-T specifications were not inspected by the compiler of this page at this time.

Adoption Not investigated for this page.
    Licensing and patents VoiceAge holds related patents and offers licensing. An Open AMR-WB Initiative (active between 2005 and 2012) made a free codec for Windows available for non-commercial use. However, this initiative cannot be found on the VoiceAge site as of October 2013. See Open AMR-WB Initiative page from Oct 2012 via Internet Archive.
Transparency Depends upon algorithms and tools to read; will require sophistication to build tools.
Self-documentation Not investigated for this page.
External dependencies Not investigated for this page.
Technical protection considerations Not investigated for this page.

Quality and functionality factors Explanation of format description terms

Sound
Normal rendering Not investigated for this page.
Fidelity (high audio resolution) The available bitrates are: 6.60, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05 and 23.85 kbps. The lowest rate that provides excellent speech quality in a clean environtment is 12.65 kbps. Higher rates are useful in background noise conditions and in the case of music. Rates of 6.60 and 8.85 provide reasonable quality when compared to narrow band codecs like AMR.
Multiple channels None.
Functionality beyond normal rendering Not investigated for this page.

File type signifiers Explanation of format description terms

Tag Value Note
Filename extension See related format.  See AMR; Comments welcome
Internet Media Type audio/AMR-wb
 
Magic numbers Hex: 0x2321414d522d57420a
ASCII: #!AMR-WB\n
From RFC 4867

Notes Explanation of format description terms

General From the VoiceAge Web site (consulted in April 2007, now linked via Internet Archive, after redesign of VoiceAge site): Most speech coding systems in use today are based on telephone-bandwidth narrowband speech, nominally limited to about 200-3400 Hz and sampled at a rate of 8 kHz. This limitation built into the public switched telephone network (PSTN) dates back to the first transcontinental telephone service at the beginning of the 20th century and imposes a constraint on communication quality. Today, the increasing penetration of end-to-end digital networks such as the second- and third-generation wireless systems (2G and 3G) and voice over packet networks permits the use of wider speech bandwidth. . . . The AMR-WB speech codec utilizes the ACELP (Algebraic Code Excitation Linear Prediction) technology, which is also employed in the AMR narrowband and EFR speech codecs as well as in ITU-T G.729 and G.723.1 at 5.3 kbit/s, among others. The AMR-WB speech codec consists of nine speech codec modes with bit rates of 23.85, 23.05, 19.85, 18.25, 15.85, 14.25, 12.65, 8.85 and 6.6 kbps. AMR-WB also includes a background noise mode that is designed to be used in discontinuous transmission (DTX) operation in GSM and as a low bit rate source-dependent mode for coding background noise in other systems. In GSM the bit rate of this mode is 1.75 kbps. . . . Wideband speech coding results in major subjective improvements in speech quality. Compared to narrowband telephone speech, low-frequency enhancement in AMR-WB from 50 to 200 Hz contributes to increased naturalness, presence, and comfort. The high-frequency extension from 3400 to 7000 Hz provides better fricative differentiation (for example, between words like fin and thin), and therefore higher intelligibility. The adoption of AMR-WB by ETSI/3GPP and ITU-T (where it is referred to as G.722.2) is of significant importance because, for the first time, the same codec has been adopted for wireless as well as wireline services. This eliminates the need for transcoding and eases the implementation of wideband voice applications and services across a wide range of communication systems and platforms.
History  

Format specifications Explanation of format description terms


Useful references

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Last Updated: Thursday, 20-Feb-2014 07:31:33 EST