초록 ▼

A codebook excited linear prediction coding system providing improved digital speech coding for high quality speech at low bit rates with side-by-side codebooks for segments of the modeled input signal to reduce the complexity of the codebook search. A linear predictive filter responsive to an input

A codebook excited linear prediction coding system providing improved digital speech coding for high quality speech at low bit rates with side-by-side codebooks for segments of the modeled input signal to reduce the complexity of the codebook search. A linear predictive filter responsive to an input signal desired to be modeled is used for identifying a basis vector from a first codebook over predetermined intervals as a subset of the input signal. A long term predictor and a vector quantizer provide synthetic excitation of modeled waveform signal components corresponding to the input signal desired to be modeled from side-by-side codebooks by providing codevectors with concatenated signals identified from the basis vector over the predetermined intervals with respect to the side-by-side codebooks. Once a codevector is identified, the codebook at the next segment is searched and a concatenation of codevectors is provided by selecting up to but not including the current segment. The codevector is treated as an additional basis vector for the codebook search at the current segment. It is possible to significantly reduce the complexity of the VSELP codebook search by precomputing and storing the terms for the code search that do not change from segment to segment. Using these techniques, the complexity of searching a 45 bit VSELP codebook (N=40, M=45, M'=9, J=5) was found to be approximately equivalent to searching a traditionally structured 10 bit VSELP codebook (N=40, M=10, J=1). A concatenation of codevectors or carry-along basis vectors are formed as a concatenation of VSELP codevectors selected up to but not including the current segment.

대표청구항 ▼

What is claimed is: 1. A codebook excited linear prediction (CELP) coding system comprising: a first excitation codebook; a first selector for selecting a codevector from the first excitation codebook; a second excitation codebook comprising a VSELP codebook, with the codevector being selected from

What is claimed is: 1. A codebook excited linear prediction (CELP) coding system comprising: a first excitation codebook; a first selector for selecting a codevector from the first excitation codebook; a second excitation codebook comprising a VSELP codebook, with the codevector being selected from the first excitation codebook used as an additional VSELP basis vector for searching the second codebook; a second selector for selecting a codevector from the second excitation codebook; and an output generator for providing at least one codeword that is a function of at least the first selected codevector and the second selected codevector while intentionally using a same gain value for each of the first and second selected codevector. 2. A coding system as recited in claim 1, wherein said first excitation codebook comprises a VSELP codebook. 3. A coding system as recited in claim 1, comprising an index generated from said first selector, said index corresponding to the selected codevector from said first codebook, wherein said output generator provides the codeword as a function at least of the first index. 4. A coding system as recited in claim 3, comprising a second index generated from said second selector, said second index corresponding to the selected codevector from said second codebook. 5. A coding system as recited in claim 1, comprising: a third excitation codebook comprising a second VSELP codebook, with an additional VSELP basis vector at least dependent on a linear superposition of the codevector selected from the first excitation codebook and of the codevector selected from the second excitation codebook, said additional VSELP basis vector is provided for searching the third codebook; a third selector for selecting a codevector from the third excitation codebook; and said output generator providing said at least one codeword as a function of the first selected codevector, the second selected codevector, and the third selected codevector. 6. A coding system as recited in claim 5, wherein said first selector selects the first codevector from the first codebook to generate an index for the selected codevector from the first codebook, said second selector selects the second codevector from the second codebook to generate an index for the selected codevector from the second codebook, and said third selector selects the third codevector from the third codebook to generate an index for the selected codevector from the third codebook; and said output generator provides at least one codeword as a function of the first index, the second index, and the third index. 7. A codebook excited linear prediction (CELP) coding system comprising: a first excitation codebook; a linear predictive filter responsive to an input signal desired to be modeled for identifying a codevector over predetermined intervals as a subset of the input signal; a selector for identifying a preferred codevector, said selector defining an additional basis vector for a second excitation codebook as a function of at least the codevector identified from said first codebook wherein both the additional basis vector and a basis vector as corresponds to the first excitation codebook intentionally have a same gain value applied thereto; a vector quantizer for synthetic excitation for modeling waveform signal components corresponding to the input signal desired to be modeled. 8. A coding system as recited in claim 7, comprising a long term predictor responsive to at least the input signal. 9. A coding system as recited in claim 7, wherein the codevector identified over the predetermined intervals is derived from said first codebook for use by said linear predictive filter for modeling the waveform signal components over the predetermined intervals. 10. A coding system as recited in claim 9, further comprising a second codebook comprising a VSELP codebook that includes said additional basis vector for identifying a codevector over a second predetermined interval corresponding to the input signal desired to be modeled by concatenation with signals generated from the selected codevector from the first codebook and the codevectors from said second codebook. 11. A coding system as recited in claim 10, wherein the additional basis vector for said second codebook comprises a carry-along basis vector. 12. A coding system as recited in claim 11, wherein the input signal desired to be modeled is divided into J predetermined intervals each of which correspond to codebooks each comprising M' basis vectors. 13. A coding system as recited in claim 12, wherein the M' basis vectors span K samples, wherein K is equal to the subframe length N of the input signal desired to be modeled. 14. A coding system as recited in claim 12, wherein J codebooks each comprising M' bit basis vectors over the predetermined intervals each provide a subset of the input signal desired to be modeled. 15. A coding system as recited in claim 14, wherein each of said J codebooks correspond to side-by-side segments of the modeled input signal to reduce the complexity of the codebook search. 16. A coding system as recited in claim 15, wherein said selector includes a generator that precomputes energy terms G for identical side-by-side segments of the modeled input signal. 17. A coding system as recited in claim 14, wherein each of the J codebooks contain identical M' basis vectors. 18. A method of generating codevectors from an excitation codebook for synthetic excitation to model waveform signal components, comprising: inputting a first codebook as a set of M' basis vectors; generating at least one selector codeword; modeling a waveform signal component from said codebook vectors by performing linear transformations on said M' basis vectors; inputting a carry-along basis vector based on at least the first selector codeword for a second codebook, wherein both the carry-along basis vector and the first selector codeword have a same gain value intentionally applied thereto; and modeling an additional waveform signal component by performing linear transformations on said second codebook. 19. A method for synthetic excitation of modeled waveform signal components as recited in claim 18, wherein the selector for the first codebook identifies a codevector for a predetermined interval as a subset of an input signal modeled waveform component over the predetermined interval. 20. A method for synthetic excitation of modeled waveform signal components as recited in claim 19, comprising identifying a codevector over a second predetermined interval from the second codebook corresponding to the modeled waveform for concatenation with signals generated from the codevector of the first codebook. 21. A method for synthetic excitation of modeled waveform signal components as recited in claim 20, wherein the input signal desired to be modeled is divided into J predetermined intervals each of which corresponds to codebooks each comprising M' basis vectors. 22. A method for synthetic excitation of modeled waveform signal components as recited in claim 21, wherein the M' basis vectors span K samples equal to the subframe length N of the modeled signal. 23. A method for synthetic excitation of modeled waveform signal components as recited in claim 22, wherein J codebooks each comprise M' basis vectors over the predetermined intervals each providing a subset of the input signal desired to be modeled. 24. A method for synthetic excitation of modeled waveform signal components as recited in claim 23, wherein each of the J codebooks are provided as identical codebooks each containing M' basis vectors.