Title :
Two novel lossless algorithms to exploit index redundancy in VQ speech compression
Author :
Sridharan, Sridha ; Leis, John
Author_Institution :
Speech Res. Lab., Queensland Univ. of Technol., Brisbane, Qld., Australia
Abstract :
We address the problem of speech compression at very low rates, with the short-term spectrum compressed to less than 20 bits per frame. Current techniques apply structured vector quantization (VQ) to the short-term synthesis filter coefficients to achieve rates of the order of 24 to 26 bits per frame. We show that temporal correlations in the VQ index stream can be introduced by dynamic codebook ordering, and that these correlations can be exploited by lossless coding approaches to reduce the number of bits per frame of the VQ scheme. The use of lossless coding ensures that no additional distortion is introduced, unlike other interframe techniques. We then detail two constructive algorithms which are able to exploit this redundancy. The first method is a delayed-decision approach, which dynamically adapts the VQ codebook to allow for efficient entropy coding of the index stream. The second is based on a vector sub-codebook approach, and does not incur any additional delay. Experimental results are presented for both methods to validate the approach
Keywords :
adaptive codes; correlation methods; data compression; delays; entropy codes; filtering theory; spectral analysis; speech coding; vector quantisation; VQ index stream; VQ speech compression; adaptive codebook; delayed-decision approach; dynamic codebook ordering; entropy coding; experimental results; index redundancy; lossless algorithms; lossless coding; short-term spectrum; short-term synthesis filter coefficients; split vector quantizer; structured vector quantization; temporal correlations; vector sub-codebook; very low rates; Australia; Books; Delay; Filters; Laboratories; Signal processing algorithms; Speech processing; Speech synthesis; Training data; Vector quantization;
Conference_Titel :
Acoustics, Speech and Signal Processing, 1998. Proceedings of the 1998 IEEE International Conference on
Conference_Location :
Seattle, WA
Print_ISBN :
0-7803-4428-6
DOI :
10.1109/ICASSP.1998.674366