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Programmable Gain Driven Linear Pcm to Mu-Law Conversion

IP.com Disclosure Number: IPCOM000044656D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Galand, C: AUTHOR [+2]

Abstract

In a digital voice transmission wherein logarithmic code conversion and gain control operations have to be performed consecutively, both operations may be combined judiciously. In the system considered here, the logarithmic code conversion is a 12- to 8-bit conversion performed in a dichotomic two-step process. This process is based on the use of T prestored values representing the extremities of segments, which segments represent the consecutive elements of the logarithmic function. Each voice signal sample to be code converted is first compared to the T1-T8 (T values) in the dichotomic process to determine the two values between which said sample is located. Then the 8-bit determination is performed by considering the slope of the segment joining the two determined values.

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Programmable Gain Driven Linear Pcm to Mu-Law Conversion

In a digital voice transmission wherein logarithmic code conversion and gain control operations have to be performed consecutively, both operations may be combined judiciously. In the system considered here, the logarithmic code conversion is a 12- to 8-bit conversion performed in a dichotomic two-step process. This process is based on the use of T prestored values representing the extremities of segments, which segments represent the consecutive elements of the logarithmic function. Each voice signal sample to be code converted is first compared to the T1-T8 (T values) in the dichotomic process to determine the two values between which said sample is located. Then the 8-bit determination is performed by considering the slope of the segment joining the two determined values. Using such a process enables easily combining the code conversion operation with a gain operation. Prior to starting the dichotomic operation the T1- T8 values are shifted right or left a number of steps corresponding to the binary value of the gain to be applied.

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