Digital speech coder having improved vector excitation source
First Claim
1. A means for providing a set of 2M codebook vectors for a vector quantizer, said codebook vector providing means comprising:
- memory means for storing said set of codebook vectors, said set of stored codebook vectors formed by;
converting a set of selector codewords into a plurality of interim data signals;
inputting a set of M basis vectors;
multiplying said set of basis vectors by said plurality of interim data signals to produce a plurality of interim vectors; and
summing said plurality of interim vectors to produce said set of codebook vectors;
means for addressing said memory means with a particular codeword; and
means for outputting a particular codebook vector from said memory means when addressed with said particular codeword.
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Accused Products
Abstract
An improved excitation vector generation and search technique (FIG. 1) is described for a code-excited linear prediction (CELP) speech coder (100) using a codebook memory of excitation code vectors. A set of M basis vectors vm (n) are used along with the excitation signal codewords (i) to generate the codebook of excitation vectors ui (n) according to a "vector sum" technique (120) of converting stored selector codewords into a plurality of interim data signals, multiplying the set of M basis vectors by the interim data signals, and summing the resultant vectors to produce the set of 2M codebook vectors. Only M basis vectors need to be stored in memory (114), as opposed to all 2M code vectors.
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Citations
12 Claims
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1. A means for providing a set of 2M codebook vectors for a vector quantizer, said codebook vector providing means comprising:
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memory means for storing said set of codebook vectors, said set of stored codebook vectors formed by; converting a set of selector codewords into a plurality of interim data signals;
inputting a set of M basis vectors;multiplying said set of basis vectors by said plurality of interim data signals to produce a plurality of interim vectors; and summing said plurality of interim vectors to produce said set of codebook vectors; means for addressing said memory means with a particular codeword; and means for outputting a particular codebook vector from said memory means when addressed with said particular codeword. - View Dependent Claims (2, 3)
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4. A digital memory containing a codebook of excitation vectors for use in speech analysis or synthesis, said codebook having at least 2M excitation vectors ui(n), each having N elements, where 1≦
- n≦
N, and where 0≦
i≦
2M-1, said codebook vectors generated from a set of M basis vectors vm (n), each having N elements, where 1≦
n≦
N and where 1≦
m≦
M, and from a set of 2M digital codewords Ii, each having M bits, where 0≦
i≦
2M-1, said codebook vectors generated using the steps of;}a} identifying a signal θ
im for each bit of each codeword Ii, such that θ
im has a first value if bit m of codeword Ii is of a first state, and such that θ
im has a second value if bit m of codeword Ii is of a second state; and{b} calculating said codebook of 2M excitation vectors ui (n) according to the equation;
##EQU28## where 1≦
n≦
N.
- n≦
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5. A method of reconstructing a signal from a codebook memory and from a particular excitation codeword, said signal reconstructing method comprising the steps of:
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{a} addressing a codebook memory with a particular codeword, said codebook memory having a set of excitation vectors stored therein, each of said excitation vectors having been produced by; {1} defining a plurality of interim data signals based upon said particular codeword; {2} multiplying a set of basis vectors by said plurality of interim data signals to produce a plurality of interim vectors; and {3} summing said plurality of interim vectors to produce a single excitation vector; {b} outputting, from said codebook memory, a particular excitation vector corresponding to the particular addressing codeword; and {c} signal processing said particular excitation vector to produce said reconstructed signal. - View Dependent Claims (6, 7, 8)
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9. A speech coder comprising:
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input means for providing an input vector corresponding to a segment of input speech; means for providing a set of codewords corresponding to a set of Y possible excitation vectors; memory means for storing said set of Y possible excitation vectors and for providing a particular excitation vector in response to a particular codeword, each of said set of excitation vectors having been produced by; {a} defining at least one selector codeword; {b} defining a plurality of interim data signals based upon said selector codeword; {c} inputting a set of X basis vectors, where X<
Y; and{d} generating each of said excitation vectors by performing linear transformations on said X basis vectors, said linear transformations defined by said interim data signals; said speech coder further comprising; a first signal path including; means for filtering said excitation vectors; means for comparing said filtered excitation vectors to said input vector, thereby providing comparison signals; and controller means for evaluating said set of codewords and said comparison signals, and for providing a particular codeword representative of a single excitation vector which, when passed through said first signal path, most closely resembles said input vector. - View Dependent Claims (10, 11, 12)
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Specification