Fractional excitation and other efficient transformed codebooks for CELP coding of speech
M. Delprat, C. Gruet, F. Dervaux, C. Baroux · 1992
The authors deal with the design and efficient codebooks in terms of quality and complexity for code excited linear prediction (CELP) coding of speech. For this purpose, a transformed codebook approach is proposed and it is shown that several well-known CELP schemes can be formulated in this way. Comparative results are given for different transformation matrices, including a new method called fractional excitations. Another technique based on singular value decomposition (SVD) of the impulse response matrix is introduced. In this technique an innovation sequence appears as a linear combination of a set of eigenvectors with optimally vector quantized coefficients. Preliminary results are presented for this new SVD-CELP technique. The authors describe a multi-codebook approach which enabled a significant bit rate reduction of the speech coder submitted to GSM half rate standardization.>