This paper presents the design of a full-duplex multi-rate vocoder which implements an LPC-10, CELPC and VSELPC algorithms in real time. A single commercially available digital signal processor IC, the TMS320C25, is u...This paper presents the design of a full-duplex multi-rate vocoder which implements an LPC-10, CELPC and VSELPC algorithms in real time. A single commercially available digital signal processor IC, the TMS320C25, is used to perform the digital processing. The channel interfaces are configured with the design of ASIC, and including timing and control logic circuits.展开更多
A new type of vocoder system based upon formant analysis is presented in this paper. The LMS adaptive algorithm is used for tracking formants of speech signals. The results of computer simulation show that the new voc...A new type of vocoder system based upon formant analysis is presented in this paper. The LMS adaptive algorithm is used for tracking formants of speech signals. The results of computer simulation show that the new vocoder has better synthesized speech quality.展开更多
This letter presents two improvements on 2.4 kb/s Mixed-Excitation Linear Prediction (MELP) vocoder. The one is a new parameter Redzc named energy to differential zerocrossing rate which is used in adaptation of V/UV ...This letter presents two improvements on 2.4 kb/s Mixed-Excitation Linear Prediction (MELP) vocoder. The one is a new parameter Redzc named energy to differential zerocrossing rate which is used in adaptation of V/UV decision of transitional segments and low energy level speech segments. The other is a multi-path searching method for Multi-Stage Vector Quantization (MSVQ) of line spectral frequency. Subjective tests show that the intelligiblity and naturallity of improved MELP vocoder are preferable to those of the original one.展开更多
The description precision of an excitation signal greatly influences the quality of reconstructed speech in low bit rate vocoders.To improve the reconstruction quality,the DCT_M model is proposed to express the excita...The description precision of an excitation signal greatly influences the quality of reconstructed speech in low bit rate vocoders.To improve the reconstruction quality,the DCT_M model is proposed to express the excitation spectral parameter,which transforms the variable length vector to fixed dimension vector through DCT transformation.It then quantizes the fixed length vector using multi-stage vector quantization.Tests show that the proposed method can keep the shape of the entire spectral envelope and reduce model error thus greatly improve the description precision.Test results in the sine excitation linear prediction(SELP)vocoder show that the DCT_M model can improve the naturalness of reconstructed speech,with subjective test score of 65%.展开更多
Although CELP coding has provided good quality synthetic speech at medium and low bit rates,the computation of an exhaustive search for stochastic codebook is extremely complex. This paper studies the exhaustive searc...Although CELP coding has provided good quality synthetic speech at medium and low bit rates,the computation of an exhaustive search for stochastic codebook is extremely complex. This paper studies the exhaustive search procedure for determining the optimum excitation,and develops an effective search method by using improved populating codebook as excitation source. The computational cost of CELP coder was reduced to 1/26 that of a conventional full-gaussian codebook search.展开更多
文摘This paper presents the design of a full-duplex multi-rate vocoder which implements an LPC-10, CELPC and VSELPC algorithms in real time. A single commercially available digital signal processor IC, the TMS320C25, is used to perform the digital processing. The channel interfaces are configured with the design of ASIC, and including timing and control logic circuits.
文摘A new type of vocoder system based upon formant analysis is presented in this paper. The LMS adaptive algorithm is used for tracking formants of speech signals. The results of computer simulation show that the new vocoder has better synthesized speech quality.
文摘This letter presents two improvements on 2.4 kb/s Mixed-Excitation Linear Prediction (MELP) vocoder. The one is a new parameter Redzc named energy to differential zerocrossing rate which is used in adaptation of V/UV decision of transitional segments and low energy level speech segments. The other is a multi-path searching method for Multi-Stage Vector Quantization (MSVQ) of line spectral frequency. Subjective tests show that the intelligiblity and naturallity of improved MELP vocoder are preferable to those of the original one.
基金supported by the National Natural Science Foundation of China (Grant No.60272020).
文摘The description precision of an excitation signal greatly influences the quality of reconstructed speech in low bit rate vocoders.To improve the reconstruction quality,the DCT_M model is proposed to express the excitation spectral parameter,which transforms the variable length vector to fixed dimension vector through DCT transformation.It then quantizes the fixed length vector using multi-stage vector quantization.Tests show that the proposed method can keep the shape of the entire spectral envelope and reduce model error thus greatly improve the description precision.Test results in the sine excitation linear prediction(SELP)vocoder show that the DCT_M model can improve the naturalness of reconstructed speech,with subjective test score of 65%.
文摘Although CELP coding has provided good quality synthetic speech at medium and low bit rates,the computation of an exhaustive search for stochastic codebook is extremely complex. This paper studies the exhaustive search procedure for determining the optimum excitation,and develops an effective search method by using improved populating codebook as excitation source. The computational cost of CELP coder was reduced to 1/26 that of a conventional full-gaussian codebook search.
