Adaptive prediction differential PCM-type transmission apparatus and process with shaping of the quantization noise

Claim 2

A coding process of the adaptive prediction differential PCM type comprising the steps of: forming an error signal e t from the difference between a sample of signal y t to be coded and a prediction signal p t of said signal in which t is a sampling time; quantizing said error signal e t ; coding the quantized signal; forming a restored error signal e t from one of said quantized and coded signals; forming a restored signal y t by adding said restored error signal e t to said prediction signal p t ; and forming said prediction signal p t from said restored signals y t and e t by first and second linear filtering operations; said first operation being performed using N successive samples of y t , namely, y t , y t-1 , . . . , y t-N+1 , and comprising taking a sequence of N samples from a first sequence formed by said N samples of y t and from a second sequence obtained by orthogonalizing said N samples of y t , and multiplying said sequence of N samples respectively by coefficients A1 t , A2 t , . . . , AN t , then summing the products obtained to obtain a prediction signal py t ; said second operation being performed using P successive samples of e t , namely, e t , e t-1 , . . . , e t-p+1 , and comprising multiplying said P successive samples respectively by coefficients B1 t , B2 t , . . . , BP t and summing the products obtained to obtain a prediction signal pe t ; adjusting sequentially said coefficients A1 t , A2 t , . . . , AN t and B1 t , B2 t , . . . , BP t at each time t so that the mean power of said error signal e t is minimized; and carrying out at least one of the two following operations (a) and (b): (a) forming a linear filtering of said signal y t by using N successive samples of y t , namely, y t , y t-1 , . . . , y t-N+1 , and comprising taking a sequence of N samples from a first sequence formed by said N samples of y t and from a second sequence formed by N derivative samples obtained by orthogonalizing said N samples of y t , and multiplying said sequence of samples by N coefficients equal to the said coefficients A1 t , A2 t , . . . , AN t , then adding the products obtained to supply a filtered signal py t , then forming on the basis of said signal py t and said signal py t previously obtained by the filtering of y t , a signal pAR t equal to γ AR py t +(1-γ AR )py t , in which γ AR is a regulatable coefficient between 0 and 1 (terminals included); (b) filtering the unquantized error signal e t by multiplying P successive samples of said signal e t , namely, e t , e t-1 , . . . , e t-P+1 , by P coefficients equal respectively to said coefficients B1 t , B2 t , . . . , BP t and adding the products obtained, to supply a filtered signal pe t , then forming on the basis of said signal pe t and the signal pe t obtained previously by filtering e t a signal pMA t which is equal to γ MA pe t +(1-γ MA )pe t , in which γ MA is a regulatable coefficient between 0 and 1 (terminals included), the coefficients γ AR and γ MA not being simultaneously zero; and after said operations (a) and (b) adding the signals pAR t and pMA t , then delaying one sampling time of the sum obtained, to supply said prediction signal p t .

Claim 3

A process according to claim 1, wherein said orthogonalizing of said N successive samples of y t is performed by means of filtering with N-1 coefficients R1 t , R2 t , . . . , R(N-1) t recursively by adjusting said N-1 coefficients, said filtering supplying N orthogonal samples ε1 t , ε2 t , . . . , εN t , which are said derivative samples, then multiplying said derivative samples by said coefficients A1 t , A2 t , . . . , AN t ; and said orthogonalizing of said N successive samples of y t is performed by means of filtering with N-1 coefficients R1 t , R2 t , . . . , R(N-1) t , said filtering supplying N orthogonal samples ε1 t , ε2 t , . . . , εN t which are said derivative samples, then multiplying said derivative samples by the coefficients A1 t , A2 t , . . . , AN t .

Claim 4

A coding apparatus of the adaptive prediction differential PCM type, comprising a subtractor with two inputs receiving a sample of the signal to be coded y t and a prediction signal p t in which t is a sampling time and an output supplying an error signal e t , a quantizer of the error signal e t , followed by a coder of the quantized signal, a circuit able to form a restored error signal e t from the quantized or coded signal, an adder with two inputs receiving the restored error signal and the prediction signal p t and with an output supplying a restored signal y t and a predictor receiving the restored signals y t and e t and supplying the said prediction signal p t , said predictor comprising two linear filters, the first acting on the restored signal y t and comprising N circuits for the formation of coefficients A1 t , A2 t , . . . , AN t , a first group of N multipliers with two inputs respectively receiving N successive samples of y t to be filtered, i.e. y t , y t-1 , . . . , y t-N+1 (or derived samples) and said N coefficients and an adder with N inputs connected to N multipliers of the first group and with an output supplying a prediction signal py t , the second comprising P circuits for the formation of P coefficients B1 t , B2 t , . . . , BP t and a second group of P multipliers with two inputs respectively receiving the P successive samples of e t , i.e. e t , e t-1 , . . . , e t-P+1 and said P coefficients and an adder with P inputs connected to the P multipliers of the second group and with an output supplying a prediction signal pe t , said two filters comprising means for sequentially adjusting at each time t the coefficients A1 t , . . . , AN t and B1.sub. t, . . . , BP t in such a way that the mean power of the error signal e t is minimal, wherein the predictor comprises means for shaping the spectrum of the quantization noise on y t (i.e. Δy t =y t -y t ) by arranging said spectrum in parallel with that of the restored signal y t , said means comprising: (A) at least one of the following circuits: (a) a first circuit constituted by a filter of signal y t comprising a first group of N multipliers with two inputs respectively receiving N successive samples of y t , i.e. y t , y t-1 , . . . , y t-N+1 (or derived samples) and N coefficients respectively equal to said coefficients A1 t , A2 t , . . . , AN t sampled in the first filter of the predictor acting on y t and an adding circuit with N inputs connected to the N multipliers of the first group and with an output supplying a filtered signal py t and by a first algebraic circuit with two inputs, one connected to the output of the filter of y t and receiving the signal py t and the other connected to the output of the filter of y t and receiving the signal py t , said first algebraic circuit supplying at one output a signal pAR t equal to γ AR py t +(1-γ AR ) py t , in which γ AR is a regulatable coefficient between 0 and 1 (terminals included); (b) a second circuit constituted by a filter of the unquantized error signal e t comprising a second group of P multipliers with two inputs respectively receiving P successive samples of e t , i.e. e t , e t-1 , . . . , e t-P+1 and P coefficients equal then respectively to said coefficients B1 t , B2 t , . . . , BP t sampled in the second filter of the predictor acting on e t and an adder with P inputs connected to P multipliers of the second group and with an output supplying a filtered signal pe t and by a second algebraic circuit with two inputs, one connected to the output of the filter of e t and receiving the signal pe t and the other to the output of the filter of e t and receiving the signal pe t , said second algebraic circuit supplying at an output a signal pMA t equal to γ MA pe t +(1-γ MA )pe t , in which γ MA is a regulatable coefficient between 0 and 1 (terminals included), the coefficients γ MA and γ AR not being simultaneously zero; (B) an adder with two inputs connected to the outputs of the first and second algebraic circuits and with an output supplying a signal pAR t +PMA t ; (C) a circuit with a delay of one sampling period with an input connected to the output of the adder and an output supplying the said prediction signal p t .

Claim 5

A coding apparatus of the adaptive prediction differential PCM type, comprising a subtractor with two inputs receiving a sample of the signal to be coded y t and a prediction signal p t in which t is a sampling time and an output supplying an error signal e t , a quantizer of the error signal e t , followed by a coder of the quantized signal, a circuit able to form a restored error signal e t from the quantized or coded signal, an adder with two inputs receiving the restored error signal and the prediction signal p t and with an output supplying a restored signal y t and a predictor receiving the restored signals y t and e t and supplying the said prediction signal p t , said predictor comprising two linear filters, the first acting on the restored signal y t and comprising N circuits for the formation of coefficients A1 t , A2 t , . . . , AN t , a first group of N multipliers with two inputs respectively receiving N successive samples of y t to be filtered, i.e. y t , y t-1 , . . . , y t-N+1 (or derived samples) and said N coefficients and an adder with N inputs connected to N multipliers of the first group and with an output supplying a prediction signal py t , the second comprising P circuits for the formation of P coefficients B1 t , B2 t , . . . , BP t and a second group of P multipliers with two inputs respectively receiving the P successive samples of e t , i.e. e t , e t-1 , . . . , e t-P+1 and said P coefficients and an adder with P inputs connected to the P multipliers of the second group and with an output supplying a prediction signal pe t , said two filters comprising means for sequentially adjusting at each time t the coefficients A1 t , . . . , AN t and B1.sub. t, . . . , BP t in such a way that the mean power of the error signal e t is minimal, wherein the predictor comprises means for shaping the spectrum of the quantization noise on y t (i.e. Δy t =y t -y t ) by arranging said spectrum in parallel with that of the restored signal y t , said means comprising: (A) at least one of the following circuits: (a) a first circuit constituted by a filter of signal y t comprising a first group of N multipliers with two inputs respectively receiving N successive samples of y t , i.e. y t , y t-1 , . . . , y t-N+1 (or derived samples) and N coefficients respectively equal to said coefficients A1 t , A2 t , . . . , AN t sampled in the first filter of the predictor acting on y t and an adding circuit with N inputs connected to the N multipliers of the first group and with an output supplying a filtered signal py t and by a first algebraic circuit with two inputs, one connected to the output of the filter of y t and receiving the signal py t and the other connected to the output of the filter of y t and receiving the signal py t , said first algebraic circuit supplying at one output a signal pAR t equal to γ AR py t +(1-γ AR ) py t , in which γ AR is a regulatable coefficient between 0 and 1 (terminals included); (b) a second circuit constituted by a filter of the unquantized error signal e t comprising a second group of P multipliers with two inputs respectively receiving P successive samples of e t , i.e. e t , e t-1 , . . . , e t-P+1 and P coefficients equal then respectively to said coefficients B1 t , B2 t , . . . , BP t sampled in the second filter of the predictor acting on e t and an adder with P inputs connected to P multipliers of the second group and with an output supplying a filtered signal pe t and by a second algebraic circuit with two inputs, one connected to the output of the filter of e t and receiving the signal pe t and the other to the output of the filter of e t and receiving the signal pe t , said second algebraic circuit supplying at an output a signal pMA t equal to γ MA pe t +(1-γ MA )pe t , in which γ MA is a regulatable coefficient between 0 and 1 (terminals included), the coefficients γ MA and γ AR not being simultaneously zero; (B) an adder with two inputs connected to the outputs of the first and second algebraic circuits and with an output supplying a signal pAR t +PMA t ; (C) a circuit with a delay of one sampling period with an input connected to the output of the adder and an output supplying the said prediction signal p t .

Claim 6

An apparatus according to claim 3, wherein the first filter of the predictor acting on y t is preceded by a first orthogonalizing circuit (28a) of the N successive samples y t , y t-1 , . . . , y t-N+1 , said circuit comprising a lattice filter with N-1 coefficients R1 t , R2 t , . . . , R(N-1) t which are recursively adjusted, said circuit having N outputs (281/1,281/2 . . . 281/N) supplying N orthogonal samples ε1 t ,ε2 t , . . . , εN t which constitute the said sample derivatives, which are applied to the inputs of the N multipliers (22/1, 22/2 . . . 22/N) of the filter of y t , the filter of y t also being preceded by a second orthogonalizing circuit (36) with a lattice filter which receives N successive samples of y t , namely y t , y t-1 , . . . , y t-N+1 and N-1 coefficients R1 t , R2 t , . . . , R(N-1) t sampled in the orthogonalizing circuit (28a) of the first filter acting on y t , said second circuit having N outputs (362/1,362/2, . . . , 362/N) supplying N orthogonal samples ε1 t , ε2 t , . . . , εN t which constitute the sample derivatives, which are then applied to the inputs of the N multipliers (32/1, 32/2 . . . 32/N) of the filter of y t .