Interpolating the history improved excitation coding for high quality CELP coding

A procedure is presented where the conventional innovation codebook approach of CELP coding is replaced by an interpolative scheme. A generalized LTP-codebook constitutes the basis for the interpolation. A pre-requisite to efficient interpolation concerns establishing the neighboring vectors of a given LTP entry. We discuss several working approximations for establishing a suitable neighborhood concept. By simulations we have found that the interpolative scheme leads to 17-20 bits for the excitation coding of one block. In addition to this, some 3-4 bits are required for block gain. A standard CELP typically spends 25 bits or more for one block of excitation coding. The subjective quality of our proposed coding scheme compares favorably with standard CELP. In particular, the interpolation improves the pitch-related properties giving a less noisy subjective impression.

[1]  Per Hedelin.  Spectral Coding at 20 bits , 1994 .

[2]  Per Hedelin.  A multi-stage perspective on CELP speech coding , 1992, [Proceedings] ICASSP-92: 1992 IEEE International Conference on Acoustics, Speech, and Signal Processing.

[3]  John Makhoul,et al.  Adaptive noise spectral shaping and entropy coding in predictive coding of speech , 1979 .

[4]  Peter Kroon,et al.  Pitch predictors with high temporal resolution , 1990, International Conference on Acoustics, Speech, and Signal Processing.

[5]  Manfred R. Schroeder,et al.  Code-excited linear prediction(CELP): High-quality speech at very low bit rates , 1985, ICASSP '85. IEEE International Conference on Acoustics, Speech, and Signal Processing.

[6]  Roar Hagen,et al.  A robust single-stage vq for spectral coding , 1993, Proceedings., IEEE Workshop on Speech Coding for Telecommunications,.

[7]  Kuldip K. Paliwal,et al.  Efficient vector quantization of LPC parameters at 24 bits/frame , 1990, [Proceedings] ICASSP 91: 1991 International Conference on Acoustics, Speech, and Signal Processing.