| G.722.2 | |
|---|---|
| Wideband coding of speech at around 16 kbit/s using Adaptive Multi-Rate Wideband (AMR-WB) | |
| Status | In force |
| Year started | 2002 |
| Latest version | (08/18) August 2018 |
| Organization | ITU-T |
| Committee | ITU-T Study Group 16 |
| Domain | telecommunication |
| License | Freely available |
| Website | https://www.itu.int/rec/T-REC-G.722.2 |
Adaptive Multi-Rate Wideband (AMR-WB) is apatentedwidebandspeechaudio coding standard developed based onAdaptive Multi-Rate encoding, using a similar methodology toalgebraic code-excited linear prediction (ACELP). AMR-WB provides improved speech quality due to a wider speech bandwidth of 50–7000 Hz compared tonarrowband speech coders which in general are optimized forPOTS wireline quality of 300–3400 Hz. AMR-WB was developed byNokia[1] and VoiceAge and it was first specified by 3GPP.[2]
AMR-WB is codified as G.722.2, anITU-T standard speech codec, formally known asWideband coding of speech at around 16 kbit/s using Adaptive Multi-Rate Wideband (AMR-WB). G.722.2 AMR-WB is the same codec as the3GPP AMR-WB. The corresponding 3GPP specifications are TS 26.190 for the speech codec[3] and TS 26.194 for the Voice Activity Detector.[4]
The AMR-WB format has the following parameters:[5]
A commonfile extension for the AMR-WB file format is.awb. There also exists another storage format for AMR-WB that is suitable for applications with more advanced demands on the storage format, like random access or synchronization with video. This format is the 3GPP-specified3GPcontainer format, based on theISO base media file format.[7] 3GP also allows use of AMR-WB bit streams for stereo sound.
AMR-WB operates, likeAMR, with nine different bit rates. The lowest bit rate providing excellent speech quality in a clean environment is 12.65 kbit/s. Higher bit rates are useful in background noise conditions and for music. Also, lower bit rates of 6.60 and 8.85 kbit/s provide reasonable quality, especially when compared to narrow-band codecs.
The frequencies from 6.4 kHz to 7 kHz are only transmitted in the highest bitrate mode (23.85 kbit/s), while in the rest of the modes the decoder generates sounds by using the lower frequency data (75–6400 Hz) along with random noise (in order to simulate the high frequency band).[8]
All modes are sampled at 16 kHz (using 14-bit resolution) and processed at 12.8 kHz.
The bit rates are the following:
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.)"[9]
When used in mobile phone networks, there are three different configurations (combinations of bitrates) that may be used for voice channels:
This limitation was designed to simplify the negotiation of bitrate between the handset and the base station, thus vastly simplifying the implementation and testing. All other bitrates can still be used for other purposes in mobile phone networks, including multimedia messaging, streaming audio, etc.
AMR-WB has been standardized by a mobile phone manufacturer consortium for future usage in networks such asUMTS. Its speech quality is high, but older networks will have to be upgraded to support a wideband codec.[citation needed]
In October 2006, the first AMR-WB tests were conducted in a deployed network by T-Mobile in Germany, in cooperation with Ericsson.[10][11]
In 2007 an end-to-end AMR-WB TrFO capable 3G & VoIP product line was commercially released byNSN (M13.6MSS, U3CMGW). AMR-WB TFO support was commercially released in 2008 (M14.2, U4.0). End-to-end TFO/TrFO negotiation and mid-call optimization (e.g. onhandover,CF orCT events) was released in 2009 (M14.3, U4.1).
In late 2009,Orange UK announced that it would be introducing AMR-WB on its network in 2010.[12][13] In FranceOrange S.A. and SFR are using AMR-WB format on their 3G+ networks since the end of summer 2010.
WIND Mobile in Canada launched HD Voice (AMR-WB) on its 3G+ network in February, 2011. WIND Mobile also announced that several handsets will support HD Voice (AMR-WB) in the first half of 2011,[14] with the first one being Alcatel Tribe.[15]
In January 2013, T-Mobile became the first GSM/UMTS based network in the US to enable AMR-WB.[16]
In Feb 2013, Chunghwa Telecom became the first GSM/UMTS based network in Taiwan to enable AMR-WB.[17]
In August 2013 the AMR-WB standard was introduced in Ukraine by Kyivstar.[18]
Nokia developed[19] theVMR-WB format forCDMA2000 networks, which is fully interoperable with 3GPP AMR-WB. AMR-WB is also a widely adapted format in mobile handsets for ringtones.[20]
The AMR wideband speech format shall be supported in3G multimedia services whenwideband speech working at 16 kHz sampling frequency is supported. This requirement is defined in 3GPP technical specifications forIP Multimedia Subsystem (IMS),Multimedia Messaging Service (MMS) and Transparent end-to-end Packet-switched Streaming Service (PSS).[21][22][23] In 3GPP specifications is AMR-WB format also used in 3GP container format.
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The patent for AMR expired in 2024.[24] Previously G.722.2 was licensed by VoiceAge Corporation.[25][26][27][28]
For encoding and decoding AMR-WB, an open-source library namedOpenCORE exists. The OpenCORE codec can be used inffmpeg.
For encoding, another open-source library exists as well, provided byVisualOn. It is included in theAndroid mobile operating system.