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1. WO1995006310 - CODEUR VOCAL ADAPTABLE A PREDICTION LINEAIRE A EXCITATION PAR CODE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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Claims
What is claimed is :
1. Apparatus for determining a codeword in a speech coder which codes a speech signal, which speech coder provides a target signal formed in response to filtering said speech signal to remove ringing information and pitch information and which speech coder provides a linear prediction coefficient synthesis filter in response to said speech signal, said apparatus comprising:
impulse response means for determining the impulse response of said synthesis filter;
a first filter for filtering said target signal with said impulse response thereby forming a search signal;
search means for searching said search signal for the position of the largest positive and largest negative values; and
formation means for forming a codeword comprising a series of values, wherein all values in the codeword are zero except for a first value and a second value, wherein said first value is positioned in said .codeword in response to the position of said largest positive value and said second value is positioned in response to the position of said largest negative value.
2. The apparatus of claim 1, wherein said first value is +1 and said second value is -1.
3. The apparatus of claim 1, wherein said impulse comprises a series of impulse response values and wherein said impulse response means comprises truncation means for truncating the number of impulse response values.
4. The apparatus of claim 3, further comprising gain means for determining a gain value in conjunction with said codeword, wherein said gain means calculates said gain value in relation to the full impulse response.
5. The apparatus of claim 1, further comprising transform means for transforming said codeword, wherein said codeword is determined in relation to being transformed.

6. The apparatus of claim 5, wherein said transform is a Hadamard transform.
7. A speech coder for converting analog speech signals to digital speech signals for transmission, said speech coder comprising:
a first filter for filtering out the spectral information from said speech signal and for providing said spectral information for transmission;
a second filter for filtering out the pitch information from said speech signal and for providing said pitch information for transmission; and
a codevector generator for determining the characteristics of a bi-pulse codevector representative of the speech signal after said spectral information and said pitch information have been filtered out and for providing said characteristics for transmission.
8. The coder of claim 7, wherein said first filter has an impulse response and wherein said codevector generator comprises a truncator for truncating said impulse response and utilizing such truncated impulse response for determining said characteristics .
9. The coder of claim 7, wherein said characteristics are capable of being determined by calculating the value a fraction having a numerator and a denominator in relation to a number of codevector possibilities, wherein said codevector generator only calculates said numerator and examines said numerators to determine which is the largest positive and largest negative.
10. The coder of claim 9, wherein said codevector generator determines a set of largest positive values and a set of largest negative values for said numerator.
11. A speech coder for converting analog speech signals to digital speech signals for transmission, said speech coder comprising:
a first filter for filtering out the spectral information from said speech signal and for providing said spectral information for transmission;

a second filter for filtering out the pitch information from said speech signal and for providing said pitch information for transmission; and
a codevector generator for determining the characteristics of a bi-pulse codevector representative of the speech signal after said spectral information and said pitch information have been filtered out and for providing said characteristics for transmission, said codevector generator comprising transform means transforming codevector possibilities from being representative of pulse-like sound to being representative of noise-like sound.
12. The coder of claim 11, wherein said transform means comprises a Hadamard transform.
13. The coder of claim 12, wherein said codevector generator further comprises a scrambler for modifying the sequency properties of transformed codevector possibilities.
14. The coder of claim 13 , wherein said characteristics are capable of being determined by calculating the value a fraction having a numerator and a denominator in relation to a number of codevector possibilities, wherein said codevector generator only calculates said numerator and examines said numerators to determine which is the largest positive and largest negative.
15. A speech coder for converting analog speech signals to digital speech signals for transmission, said speech coder comprising:
a first filter for filtering out the spectral information from said speech signal and for providing said spectral information for transmission;
a second filter for filtering out the pitch information from said speech signal and for providing said pitch information for transmission;
a first codevector generator for determining first characteristics of a bi-pulse codevector representative of the speech signal after said spectral information and said pitch information have been filtered out and for providing said first characteristics for transmission;

a second codevector generator for determining second characteristics of a bi-pulse codevector representative of the speech signal after said spectral information and said pitch information have been filtered out and for providing said second characteristics for transmission, said codevector generator comprising transform means transforming codevector possibilities from being representative of pulse-like sound to being representative of noise-like sound;
a third codevector generator for determining third characteristics of a single-pulse codevector representative of the speech signal after said spectral information and said pitch information have been filtered out and for providing said third characteristics for transmission; and
a comparator for evaluating the characteristics determined by said first, second and third codebook generators and choosing one of said first, second or third characteristics .
16. The coder of claim 15, further comprising a weightor, for providing a weighting factor to one of said first, second and third characteristics.
17. The coder of claim 16 wherein said weighting factor is provided to said second characteristics.