Table Lookup Algorithm for ADPCM Audio Codecs
Original Publication Date: 2002-Jul-11
Included in the Prior Art Database: 2002-Jul-11
This document describes an algorithm for doing a fast table lookup in an ADPCM Codecs such as the ITU-T G.726 speech vocoder. G.726 is finding wide acceptance as a standard codec for transporting voice over packet networks such as IP, ATM, and Frame Relay. In order to be competitive, a packet telephony system must be able to operate within tight real-time constraints. The method presented here will quantize a 12-bit signal in about half the time as a binary search, uses less memory, and is time-invariant in processor uses (an important feature in real-time systems).