Extended Adaptive Multi-Rate – Wideband (AMR-WB+) is an audio codec that extends AMR-WB. It adds support for stereo signals and higher sampling rates. Another main improvement is the use of transform coding (transform coded excitation – TCX) additionally to ACELP. This greatly improves the generic audio coding. Automatic switching between transform coding and ACELP provides both good speech and audio quality with moderate bit rates.
As AMR-WB operates at internal sampling rate 12.8 kHz, AMR-WB+ also supports various internal sampling frequencies ranges from 12.8 kHz to 38.4 kHz. AMR-WB uses 16 kHz sampling frequency with a resolution of 14 bits left justified in a 16-bit word. AMR-WB+ uses 16/24/32/48 kHz sampling frequencies with a resolution of 16 bits in a 16-bit word.
3GPP originally developed the AMR-WB+ audio codec for streaming and messaging services in Global System for Mobile communications (GSM) and Third Generation (3G) cellular systems. Its primary target applications are Packet-Switched Streaming service (), Multimedia Messaging Service (MMS) and Multimedia Broadcast and Multicast Service (MBMS).
The AMR-WB+ codec has a wide bit-rate range, from 5.2 to 48 kbit/s. Mono rates are scalable from 5.2 to 36 kbit/s, and stereo rates are scalable from 6.2 to 48 kbit/s, reproducing bandwidth up to 20 kHz (approaching CD quality). Moreover, it provides backward compatibility with AMR wideband.
Licensing and patent issues
AMR-WB+ compression incorporate several patents of Nokia Corporation, Telefonaktiebolaget L. M. Ericsson and VoiceAge Corporation. VoiceAge Corporation is the License Administrator for the AMR and AMR-WB+ patent pools. VoiceAge also accepts submission of patents for determination of their possible essentiality to these standards.
- Adaptive Multi-Rate (AMR)
- Adaptive Multi-Rate Wideband (AMR-WB)
- Comparison of audio coding formats
- RTP audio video profile
- 3GPP TS 26.290; Audio codec processing functions; Extended Adaptive Multi-Rate – Wideband (AMR-WB+) codec; Transcoding functions, Page 10, Retrieved on 2009-07-08
- RFC 4352, page 30
- "State-of-the-art AMR-WB+ Hi-fi Audio Compression is Now Available for Helix". sys-con. 2005-09-28. Retrieved 2009-09-11.
- "AMR-WB+ audio codec being integrated into Helix". Helix Community mailinglist. 2005-09-28. Retrieved 2009-09-11.
- VoiceAge Corporation (2007-10-14). "AMR-WB+ Licensing Terms". Archived from the original on 2007-10-14. Retrieved 2009-09-12.
- VoiceAge Corporation (November 2006). "AMR-WB+ Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12.
- VoiceAge Corporation. "Licensing – Patent Calls". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12.
- VoiceAge Corporation (2007-10-14). "Licensing – Patent Calls". Archive.org. Archived from the original on 2007-10-14. Retrieved 2009-09-12.
- 3GPP codecs specifications; 3G and beyond / GSM, 26 series
- 3GPP TS 26.290; Audio codec processing functions; Extended Adaptive Multi-Rate – Wideband (AMR-WB+) codec; Transcoding functions
- RFC 4352 – RTP Payload Format for the Extended Adaptive Multi-Rate Wideband (AMR-WB+) Audio Codec
- RFC 4281 – The Codecs Parameter for "Bucket" Media Types