Gyuhyeok Jeong

Bandwidth Scalable Wideband Codec Using Hybrid Matching Pursuit Harmonic/CELP Scheme

A novel hybrid harmonic/CELP scheme for bandwidth scalable wideband codec is proposed that utilizes a band-split technique, where the low-band (0-4 kHz) is critically subsampled and coded using 11.8 kbps G.729E. The high-band signal is divided into stationary mode (SM) and non-stationary mode (NSM) components based on its unique characteristics. In the SM portion, the high-band signal is compressed using a multi-stage coding combined sinusoidal model based on the matching pursuit (MP) algorithm and CELP with the circular codebook. In the NSM portion, the high-band signals are coded by CELP with both pulse and circular codebooks. For efficient bit allocation and enhanced performance, the pitch of the high-band codec is estimated using the quantized pitch parameter in low-band codec. In an informal listening test, the subjective speech quality was rated as comparable to that obtainable with 48 kbps G.722 and 12.85 kbps G.722.2.

Analysis-by-Synthesis Sinusoidal Model without an Overlapping Scheme

A new sinusoidal modeling approach for the analysis-by-synthesis (AbS) of parameters that characterize a linear combination of damped sinusoids is proposed. In addition to the typical sinusoidal parameters, two different damping factors, which represent the time-varying nature of speech, were used to efficiently reduce the modeling error. Even though the proposed model does not employ the overlap-adding synthesis or smoothly interpolative synthesis scheme, it shows substantially better modeling performance in the synthesis of voiced and transient segments.

A Method For Improvement Of Split Vector Quantization Of The ISF Parameters Using Adaptive Extended Codebook

This paper presents a method for improving the performance of ISF coefficients quantizer through compensating the defect of the split structure vector quantization using the ordering property of ISF coefficients. And design the ISF coefficients quantizer for wideband speech codec using proposed method. The wideband speech codec uses split structure vector quantizer which could not use the correlation between ISF coefficients fully to reduce complexity and the size of codebook. The proposed algorithm uses the ordering property of ISF coefficients to overcome the defect. Using the ordering property, the codebook redundancy could be figured out. The codebook redundancy is replaced by the adaptive-extended codebook to improve the performance of the quantizer through using the ordering property, ISF coefficient prediction and interpolation of existing codebook. As a result, the proposed algorithm shows that the adaptive-extended codebook algorithm could get about 2 bit gains in comparison with the existing split structure ISF quantizer of AMR-WB (G.722.2) in the points of spectral distortion.