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Backward Adaptation of Quantizing Resources

IP.com Disclosure Number: IPCOM000060525D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 17K

Publishing Venue

IBM

Related People

Galand, C: AUTHOR

Abstract

Subband Coding associated with adaptive (or dynamic) allocation of bit resources has been shown to be an efficient approach for digital coding of speech signals. The input signal S(n) sampled at 8 KHz, is split into p subbands. Then each subband signal is quantized by a Block Companded PCM quantizer (BCPCM). The quantizer parameters are updated per block of samples, to take into account the short-term variations of the formant's frequencies and energies. Let S(i, j) denote the j-th sample of the i-th subband, and let us assume the block duration corresponds to N subband samples. For each subband signal S(i,j), for i=1, ...,p, one determines the so-called subband characteristic: (Image Omitted) The characteristic terms are locally used to derive the bit resources which should be allocated to each subband.

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Backward Adaptation of Quantizing Resources

Subband Coding associated with adaptive (or dynamic) allocation of bit resources has been shown to be an efficient approach for digital coding of speech signals. The input signal S(n) sampled at 8 KHz, is split into p subbands. Then each subband signal is quantized by a Block Companded PCM quantizer (BCPCM). The quantizer parameters are updated per block of samples, to take into account the short-term variations of the formant's frequencies and energies. Let S(i, j) denote the j-th sample of the i-th subband, and let us assume the block duration corresponds to N subband samples. For each subband signal S(i,j), for i=1, ...,p, one determines the so-called subband characteristic:

(Image Omitted)

The characteristic terms are locally used to derive the bit resources which should be allocated to each subband. This technique may generate a long end to end delay in the transmission of coded signal, due to the necessity of processing samples by blocks to derive the C(i)'s for each block. This drawback may be avoided by using the Ci's with one block of delay. In other words, the dynamic quantizing resources are allocated to the kth block, based on the consideration of C(i)'s for the (k-1)th block.

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