Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | AMR-WB, Adaptive Multi-Rate - Wideband Speech Codec |
| 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. |
| 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 |
| 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 patent claims | Licensing for AMR-WB is handled by VoiceAge; see also Open AMR-WP Initiative. |
| 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. |
| Normal rendering for sound | Not investigated for this page. |
| Fidelity (support for 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. |
| Sound field (support for multi-channel audio) | None. |
| Functionality beyond normal sound rendering | Not investigated for this page. |
| Tag type | Value | Note |
| Filename Extension | See AMR; Comments welcome | |
| Internet Media Type | See AMR; Comments welcome | |
| Magic numbers | See AMR; Comments welcome |
| General | From the VoiceAge Web site (consulted in April 2007): 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 |
URLs
From the 3GPPP Web site, via menu page (http://www.3gpp.org/ftp/Specs/html-info/26-series.htm):
• Wikipedia AMR-WB+ entry, consulted April 2, 2007 (http://en.wikipedia.org/wiki/AMR-WB+)
• ETSI licensing and patent Web site (http://webapp.etsi.org/IPR/home.asp)
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