Modification of fixed codebook search in G.729 Annex E audio coding
First Claim
1. A method of providing a fixed codebook vector value set for ITU Recommendation G.729 Annex E compliant signal encoding, comprising the steps of:
- initializing a vector set for the fixed codebook based upon a generally even distribution of available samples;
performing a codebook search according to ITU Recommendation G.729 Annex E; and
updating said initialized vector set when said codebook search yields a vector set having a minimum mean square error value, andmaintaining said initialized vector set when said codebook search does not yield a minimum mean square error value.
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Abstract
ITU Recommendation G.729 Annex E teaches in the implementation of a fixed codebook search to determine the selected sample combination providing the minimal difference between the original input speech and the reconstructed speech after implementation of the codec. A large number of sample sets are processed and the difference between the original input signal and the reconstructed signal for each set is determined and stored in a register. Under certain conditions, the register can overflow resulting in invalid difference values. When such a condition occurs, the fixed codebook search cannot determine the sample combination providing the minimal mean square error between the weighted input speech and the weighted reconstructed speech. An initialization vector for the codvec vector is used to provide valid data which conforms to the G.729 Annex E specifications and minimizes changes to the G.729 source code while providing robust quality signal processing in the event of register overflow condition.
9 Citations
12 Claims
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1. A method of providing a fixed codebook vector value set for ITU Recommendation G.729 Annex E compliant signal encoding, comprising the steps of:
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initializing a vector set for the fixed codebook based upon a generally even distribution of available samples; performing a codebook search according to ITU Recommendation G.729 Annex E; and updating said initialized vector set when said codebook search yields a vector set having a minimum mean square error value, and maintaining said initialized vector set when said codebook search does not yield a minimum mean square error value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification