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Adaptive Bit Allocation Technique

IP.com Disclosure Number: IPCOM000043058D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Crouse, WG: AUTHOR [+2]

Abstract

This article describes a technique for dynamically allocating bits in a speech encoding device or processor. The technique is relatively fast and may be used with adaptive transform coding where a large number of samples must be quantized with their individual bit allocation. The technique favors the low frequency components which are needed to improve speech quality. The technique may utilize up to three phases to ensure the assignment of all "N" bits. The phases are identified as phase 1, phase 2, and phase 3. The flow charts which implement each of these phases on a microcomputer are given in Figs. 1 through 3. Depending on the outcome of each phase, the microcomputer may use one or all three phases of the technique to dynamically assign the available number of bits.

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Adaptive Bit Allocation Technique

This article describes a technique for dynamically allocating bits in a speech encoding device or processor. The technique is relatively fast and may be used with adaptive transform coding where a large number of samples must be quantized with their individual bit allocation. The technique favors the low frequency components which are needed to improve speech quality. The technique may utilize up to three phases to ensure the assignment of all "N" bits. The phases are identified as phase 1, phase 2, and phase 3. The flow charts which implement each of these phases on a microcomputer are given in Figs. 1 through 3. Depending on the outcome of each phase, the microcomputer may use one or all three phases of the technique to dynamically assign the available number of bits. PHASE 1 The phase 1 steps may be summarized as follows: (a) Set a test threshold equal to one-half of the maximum energy magnitude. (b) Assign a bit to all samples exceeding the threshold, then reduce those samples to one-half

their present value. (c) Lower the threshold by one-half again (now

equal to one-quarter maximum magnitude), and

proceed as in (b) above. (d) Repeat this process until the maximum

allowable number of bits are assigned or exceeded. If the maximum number of bits are assigned, end; or else go to phase 2. PHASE 2 (a) Go back one step in the phase 1 procedure as far as energy test levels and the bit assignment

are concerned. The bit assignment now has less

than...