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== Features ==
* Sampling frequency 8 kHz/13-bit (160 samples for 20 ms frames), filtered to 200–3400 Hz.
* The AMR codec uses eight source codecs with bit-rates of 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kbit/s.
* Generates frame length of 95, 103, 118, 134, 148, 159, 204, or 244 bits for AMR FR bit rates 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, or 12.2 kbit/s, respectively. AMR HR frame lengths are different.
* AMR utilizes [[Discontinuous Transmission]] (DTX), with [[Voice Activity Detection]] (VAD) and [[Comfort noise|Comfort Noise Generation]] (CNG) to reduce bandwidth usage during silence periods
* Algorithmic delay is 20 ms per frame. For bit-rates of 12.2, there is no 'algorithm' look-ahead delay. For other rates, look-ahead delay is 5 ms. Note that there is 5 ms 'dummy' look-ahead delay, to allow seamless frame-wise mode switching with the rest of rates.
* AMR is a hybrid speech coder, and as such transmits both speech parameters and a waveform signal
** [[Linear predictive coding]] (LPC) is used to synthesize the speech from a residual waveform. The LPC parameters are encoded as [[Line spectral pairs]] (LSP).
** The residual waveform is coded using [[Algebraic Code Excited Linear Prediction]] (ACELP).
* The complexity of the algorithm is rated at 5, using a relative scale where [[G.711]] is 1 and [[G.729a]] is 15.
* [[PSQM]] testing under ideal conditions yields [[Mean Opinion Score]]s of 4.14 for AMR (12.2 kbit/s), compared to 4.45 for [[G.711]] (µ-law)
* [[PSQM]] testing under network stress yields [[Mean Opinion Score]]s of 3.79 for AMR (12.2 kbit/s), compared to 4.13 for [[G.711]] (µ-law)
== Licensing and patent issues ==
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