Method and apparatus for determining the excitation signal in VS

Details Method and apparatus for determining the excitation signal in VS Method and apparatus for determining the excitation signal in VS

1992-02-14

1994-04-26

Fleming, Michael R.

G10L 900

Patent

active

053074602

ABSTRACT:
A new basis vector search process that directly results in an optimal linear weighting for a VSELP (Vector Sum Excited Linear Prediction) coder, thus avoiding the need to perform an extensive search. In the present invention, the conventional search process is replaced by a direct formula, thus avoiding the time consuming searching procedure. Using a simple mathematical relationship, the process of filtering the basis signals with an impulse response filter h(n) every subframe is avoided. A simple theorem has been developed to reduce the computation involved in carrying out the filtering of the basis signals with h(n), and is referred to as the switching convolution theorem. As a result, the computation time necessary to produce the optimal weighting is reduced by a factor of from 3 to 4, while maintaining the output quality of the coder. The new apparatus and method are based upon a set of equations that includes several experimentally justified assumptions. The apparatus and method have been implemented successfully for use in a digital cellular telephone. The present invention reduces of the complexity of VSELP coders while maintaining voice quality comparable to conventional full-search coders.

REFERENCES:
patent: 4896361 (1990-01-01), Gerson
patent: 4907276 (1990-03-01), Aldersburg
patent: 4963030 (1990-10-01), Makur
patent: 5208862 (1993-05-01), Ozawa
patent: 5214706 (1993-05-01), Minde

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