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G.721 describes a method for compressing 64 kbit/s speech signals to 32 kbit/s

.The method, known as Adaptive Delta Pulse Code Modulation (ADPCM), is based on the difference between neighbouring signals

and the prediction of the next following signal. The G.721 speech codec achieves half the data rate ofG.711 at a resolution of 4 bits at 32 kbit/s, with hardly any noticeable loss in quality. The speech quality has a Mean Opinion Score (MOS) of 4.2 in contrast to 4.4 for G.711.

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Englisch: G721
Updated at: 20.09.2011
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