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The Adaptive Multi-Rate (AMR, AMR-NB or GSM-AMR) audio codec is an audio compression format optimized for speech coding. AMR is a multi-rate narrowband speech codec that encodes narrowband (200–3400 Hz) signals at variable bit rates ranging from 4.75 to 12.2 kbit/s with toll quality [ 3 ] speech starting at 7.4 kbit/s.
AMR-WB was developed by Nokia [1] and VoiceAge and it was first specified by 3GPP. [2] AMR-WB is codified as G.722.2, an ITU-T standard speech codec, formally known as Wideband 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 the 3GPP AMR-WB.
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.
AMR audio (various) 8000 20 Adaptive Multi-Rate audio RFC 4867 dynamic (or profile) AMR-WB audio (various) 16000 20 Adaptive Multi-Rate Wideband audio (ITU-T G.722.2) RFC 4867 dynamic (or profile) AMR-WB+ audio 1, 2 or omit 72000 13.3–40 Extended Adaptive Multi Rate – WideBand audio RFC 4352 dynamic (or profile) vorbis audio (various) (various)
#!AMR: 0 amr Adaptive Multi-Rate ACELP (Algebraic Code Excited Linear Prediction) Codec, commonly audio format with GSM cell phones. 23 21 53 49 4C 4B 0A #!SILK␊ 0 sil Audio compression format developed by Skype 23 3F 52 41 44 49 41 4E 43 45 0A #?RADIANCE␊ 0 hdr Radiance High Dynamic Range image file 23 40 7E 5E #@~^ 0 vbe VBScript Encoded ...
AMR: Speech: 1999-06 Patent encumbered No Yes No Yes Yes No No Yes AMR-NB, AMR-WB: G.728: Speech: 1992-09 Expired patents No No No No Yes No No No No Speex: Speech: 2003-03 Open source [100] ACM [d] No No No No No No No No QCELP: Speech: 1994 Proprietary: No No Yes Yes No No No No 13K Other Other — Varies Musepack, WavPack, TTA, any format ...
The quality for stereo is satisfactory to modest requirements at 96 kbit/s in joint stereo mode; however, hi-fi transparency demands data rates of at least 128 kbit/s . Tests [which?] of MPEG-4 audio have shown that AAC meets the requirements referred to as "transparent" for the ITU at 128 kbit/s for stereo, and 384 kbit/s for 5.1 audio. [7]
The audio/modem riser (AMR) is a riser expansion slot found on the motherboards of some Pentium III, Pentium 4, Duron, and Athlon personal computers. It was designed by Intel to interface with chipsets and provide analog functionality, such as sound cards and modems , on an expansion card.