The Standard

G.723.1 is a dual rate speech coder standard from International Telecommunication Union–Telecommunication standardization sector (ITU-T), for compressing the toll quality speech (8000 samples/second). The typical applications of this speech coder are in telephony over packet networks, like Voice-over-Internet-Protocol (VoIP). This speech coder is extensively used for coding the speech component in the video conferencing applications and is a part of the overall H.324 family of standards.

This coder has two bit rates, 5.3 and 6.3 Kbps. Both bit rates share the same short-term analysis techniques for processing the speech. For long-term analysis of speech, the algorithms used are different. For 5.3 Kbps coder, Algebraic Code Excited Linear Prediction (ACELP) principles are used where as in 6.3 Kbps coder, Multi Pulse-Maximum Likelihood Quantization (MP-MLQ) techniques are used.

The coder works on a frame of 240 speech samples (30 msec). Besides, there is a look ahead of 60 samples (7.5 msec). So the total algorithmic delay for the coder is 37.5 msec.

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