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Very Low Complexity CELP Speech Coding with Adaptive Phase Codebooks

Authors:
Gerlach, C. G.
Book Title:
Proceedings of IEEE Workshop on Speech Coding (SCW)
Pages:
p.p. 43-44
Address:
Annapolis, Maryland, USA
Date:
Sep. 1995
Language:
English

Abstract

In analysis-by-sythesis speech coders the computational complexity of the search for an optimum innovation is still high through transformations were proposed to decrease the complexity. This limits practial codebook sizes and vector dimensions (block lengths). In [2] a transform coding interpretation of analysis-by-synthesis was started. Further it has been shown that unity magnitude codebooks in the frequency domain with the correct phase information allow near original speech quality. So unity magnitude codebooks with structured phases were proposed, that permit a computational complexity which increase only proportional to the bit rate and not to the codebook size. But in this simple approach slight perceptual degradations remained. In continuation to these ideas, an adaptive product codebook is proposed in this contribution, which allows more natural phase contours to eliminate the degradations, while keeping the complexity extreme low. Essential for the new concept, is the dynamic bit allocation to frequency intervals with variable bandwidth. conciderable improvements of both objective and subjective quality were achieved.

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