NDLI: High performance CELP coder utilizing a novel adaptive forward-backward LPC quantization

Content Provider	IEEE Xplore Digital Library
Author	Zijun Yang Vass, J. Yunxin Zhao Xinhua Zhuang
Copyright Year	1997
Description	Author affiliation: Dept. of Comput. Eng. & Comput. Sci., Missouri Univ., Columbia, MO, USA (Zijun Yang)
Abstract	A highly efficient algorithm termed adaptive forward-backward vector quantization (AFBVQ) is developed for variable bit rate quantization of linear predictive coding (LPC) coefficients and integrated with the FS1016 Federal Standard Code Excited Linear Predictive (CELP) coder. This results in a high performance low bit rate speech coder called as AFBVQ-CELP which brings in two-fold bit rate reduction by backward LPC indexing and by forward LPC VQ. In AFBVQ, a previously decoded and temporally close speech signal is re-segmented into overlapping blocks. As the LPC coefficients calculated from one of those synthetic blocks are spectrally close to the current unquantized LPC coefficients, the backward LPC indexing is used to encode the current speech block; otherwise, the forward linear prediction is practised with the split vector quantization supported by a very efficient codebook initialization termed Mixture Gaussian Clustering (MGC). When compared to FS1016 CELP coder, AFBVQ-CELP reduces the LPC bit rate by 18 bit-per-frame (bpf) at the same spectral distortion. It means the overall bit rate is reduced from 4.8 kbps (FS1016 CELP) to 4.2 kbps. Furthermore, the proposed AFBVQ consistently outperforms the traditional forward LPC VQ by 3 bpf with the same spectral distortion. Subjective listening tests show that with AFBVQ-CELP the LPC bit rate can be further reduced to 8.4 bpf, resulting in 3.94 kbps overall bit rate without compromising the decoded speech quality.
Starting Page	131
Ending Page	136
File Size	326360
Page Count	6
File Format	PDF
ISBN	0780337808
DOI	10.1109/MMSP.1997.602625
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1997-06-23
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Linear predictive coding Bit rate Decoding Vector quantization Code standards Indexing Speech coding Computer buffers Computer science Standards development
Content Type	Text
Resource Type	Article

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