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A DPCM TECHNIQUE WITH DUAL CODE ASSIGNMENT

IP.com Disclosure Number: IPCOM000024714D
Original Publication Date: 1981-Oct-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 4 page(s) / 89K

Publishing Venue

Xerox Disclosure Journal

Abstract

The proposed DPCM (Differential Pulse Code Modulation) system encodes data from 6 bits to 4 bits as shown by the encoder in Figure 1, and by the decoder in Figure 2. In general, the technique could be extended to encode from m to n bits to achieve data packing.

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XEROX DISCLOSURE JOURNAL

A DPCM TECHNIQUE WITH DUAL CODE ASSIGNMENT U.S. CI. 358/133 Henry H. Liao

                                 Proposed Classification Int. C1. H04n 7/12
The proposed DPCM (Differential Pulse Code Modulation) system encodes data from 6 bits to 4 bits as shown by the encoder in Figure 1, and by the decoder in Figure 2. In general, the technique could be extended to encode from m to n bits to achieve data packing.

Figure 1

where Xk, Xk - : the current and previous signal

              
dk = Xk - Xk-l - ek ek = qk - dk
The function of quantization and mapping of the output qk to nk is shown in Table
1. It is noticed that the n signals 11 11, 1101, 1100 have dual assignments representing quantization steps of +5k, +47, +37, respectively. The decoder shall make a decision whenever one of the three codes is presented. If the signal level is 31 or less, a positive quantization step is used; if the signal level is 32 or more, a negative quantization step is used. Furthermore, the decoded signal may overshoot (greater than 63) or undershoot (less than 0). A supressor or limiter can be used to confine the signals between 0 and 63.

Volume 6 Number 5 September/October 1981 27 1

L,

Figure 2

dk qk ek "k

Then,

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A DPCM TECHNIQUE WITH DUAL CODE ASSIGNMENT (Cont'd)

DPCM LOOK-UP TABLE

:':i +53

No in grow

11 +58 1111

11 +47 - 1101

+ 37

+28

9

9

9

1100

0111

01 10

7 +11 0111

    XEROX DISCLOSURE JOURNAL Volume 6 Number 5 September/October 1981

+ 19

+...