Editing Adaptive Multi-Rate Wideband (section)

==AMR modes==
AMR-WB operates, like [[Adaptive Multi-Rate|AMR]], with nine different bit rates. The lowest bit rate providing excellent speech quality in a clean environment is 12.65&nbsp;kbit/s. Higher bit rates are useful in background noise conditions and for music. Also, lower bit rates of 6.60 and 8.85&nbsp;kbit/s provide reasonable quality, especially when compared to narrow-band codecs.

The frequencies from 6.4&nbsp;kHz to 7&nbsp;kHz are only transmitted in the highest bitrate mode (23.85&nbsp;kbit/s), while in the rest of the modes the decoder generates sounds by using the lower frequency data (75–6400&nbsp;Hz) along with random noise (in order to simulate the high frequency band).<ref>Kuo, Sen M., Bob H. Lee, and Wenshun Tian. Real-Time Digital Signal Processing: Fundamentals, Implementations and Applications. John Wiley & Sons, 2013.</ref>

All modes are sampled at 16&nbsp;kHz (using 14-bit resolution) and processed at 12.8&nbsp;kHz.

The bit rates are the following:

* Mandatory multi-rate configuration
** 6.60&nbsp;kbit/s (used for circuit switched [[GSM]] and [[UMTS]] connections; should only be used temporarily during bad radio connections and is not considered [[Wideband audio|wideband]] speech)
** 8.85&nbsp;kbit/s (used for circuit switched GSM and UMTS connections; should only be used temporarily during bad radio connections and is not considered [[Wideband audio|wideband]] speech; provides quality equal to [[G.722]] at 48&nbsp;kbit/s for clean speech)
** 12.65&nbsp;kbit/s (main anchor bitrate; used for circuit switched GSM and UMTS connections; offers superior audio quality to AMR at and above this bit rate; provides quality equal to or better than G722 at 56&nbsp;kbit/s for clean speech)
* Higher bitrates for speech in adverse background noise environments, combined speech and music, and multi-party conferencing.
** 14.25&nbsp;kbit/s
** 15.85&nbsp;kbit/s
** 18.25&nbsp;kbit/s
** 19.85&nbsp;kbit/s
** 23.05&nbsp;kbit/s (not targeted for full-rate GSM channels)
** 23.85&nbsp;kbit/s (provides quality equal to G.722 at 64&nbsp;kbit/s for clean speech; not targeted for full-rate GSM channels)
Notes: "The codec mode can be changed every 20 ms in 3G WCDMA channels and every 40 ms in GSM/GERAN channels. (For Tandem Free Operation interoperability with GSM/GERAN, mode change rate is restricted in 3G to 40 ms in AMR-WB encoders.)" <ref>3GPP [http://www.3gpp.org/DynaReport/26976.htm 3GPP TS 26.976 – Performance characterization of the Adaptive Multi-Rate Wideband (AMR-WB) speech codec; Chapter 4.2 ] Retrieved on 2014-04-10.</ref>