Editing Adaptive Multi-Rate audio codec (section)

== Features ==
* Sampling frequency 8&nbsp;kHz/13-bit (160 samples for 20&nbsp;ms frames), filtered to 200–3400&nbsp;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&nbsp;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&nbsp;kbit/s, respectively. AMR&nbsp;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&nbsp;ms per frame. For bit-rates of 12.2, there is no "algorithm" look-ahead delay. For other rates, look-ahead delay is 5&nbsp;ms. Note that there is 5&nbsp;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&nbsp;kbit/s), compared to 4.45 for [[G.711]] (μ-law){{citation needed|date=October 2019}}
* PSQM testing under network stress yields [[mean opinion score]]s of 3.79 for AMR (12.2&nbsp;kbit/s), compared to 4.13 for [[G.711]] (μ-law)