A Unified Formulation of Segment Companding Laws and Synthesis of Codecs and Digital Compandors

fi-laiv and the A-laxv. Instantaneous companding of PCM is used to maintain a reasonablyconstant signal to quantizing noise ratio for a wide dynamic range of the input voice signal. A logarithmic "/x-law" is a typical "smooth" input/ output transfer characteristic that has been approximated in the D1 channel bank realized by a diode compandor. 1,2 In contrast to the smooth law, segment type companding laws, which are piecewise linear approximations to the continuous laws, have also been considered. In early experimental PCM systems a segment law was used primarily to avoid implementation difficulties associated with tracking of diode compandors. 3,4 However, since the mid-sixties segment laws have been reconsidered from the view point of digital linearization to cater to the possibility of digital processing in an integrated digital network. Two of the segment law families have been stressed--the 13-segment A-law,8,0 and the 15-segment /x-law used in the D2 channel bank. 7 The major advantage of the segment laws resides in the digital linearization feature, through which digital processing such as digital 1555