Adaptive prediction differential PCM-type transmission apparatus and process with shaping of the quantization noise
First Claim
1. A coding process of the adaptive prediction differential PCM type comprising the steps of:
- forming an error signal et from the difference between a sample of signal yt to be coded and a prediction signal pt of said signal in which t is a sampling time;
quantizing said error signal et ;
coding the quantized signal;
forming a restored error signal et from one of said quantized and coded signals;
forming a restored signal yt by adding said restored error signal et to said prediction signal pt ; and
forming said prediction signal pt from said restored signals yt and et by first and second linear filtering operations;
said first operation being performed using N successive samples of yt, namely, yt, yt-1, . . . , yt-N+1, and comprising taking a sequence of N samples from a first sequence formed by said N samples of yt and from a second sequence obtained by orthogonalizing said N samples of yt, and multiplying said sequence of N samples respectively by coefficients A1t, A2t, . . . , ANt, then summing the products obtained to obtain a prediction signal pyt ;
said second operation being performed using P successive samples of et, namely, et, et-1, . . . , et-p+1, and comprising multiplying said P successive samples respectively by coefficients B1t, B2t, . . . , BPt and summing the products obtained to obtain a prediction signal pet ;
adjusting sequentially said coefficients A1t, A2t, . . . , ANt and B1t, B2t, . . . , BPt at each time t so that the mean power of said error signal et is minimized; and
carrying out at least one of the two following operations (a) and (b);
(a) forming a linear filtering of said signal yt by using N successive samples of yt, namely, yt, yt-1, . . . , yt-N+1, and comprising taking a sequence of N samples from a first sequence formed by said N samples of yt and from a second sequence formed by N derivative samples obtained by orthogonalizing said N samples of yt, and multiplying said sequence of samples by N coefficients equal to the said coefficients A1t, A2t, . . . , ANt, then adding the products obtained to supply a filtered signal pyt, then forming on the basis of said signal pyt and said signal pyt previously obtained by the filtering of yt, a signal pARt equal to γ
AR pyt +(1-γ
AR)pyt, in which γ
AR is a regulatable coefficient between 0 and 1 (terminals included);
(b) filtering the unquantized error signal et by multiplying P successive samples of said signal et, namely, et, et-1, . . . , et-P+1, by P coefficients equal respectively to said coefficients B1t, B2t, . . . , BPt and adding the products obtained, to supply a filtered signal pet, then forming on the basis of said signal pet and the signal pet obtained previously by filtering et a signal pMAt which is equal to γ
MA pet +(1-γ
MA)pet, 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 pARt and pMAt, then delaying one sampling time of the sum obtained, to supply said prediction signal pt.
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Abstract
A coding process for the adaptive prediction differential PCM type. An error signal et is formed between a sample of signal yt to be coded and a prediction signal pt of said signal. The prediction signal pt is formed from restored signals yt and et by two linear filtering operations, the first relating to N successive samples of yt and using coefficients A1t, A2t, . . . , ANt and the second relating to P successive samples of et and using coefficients B1t, B2t, . . . , BPt, the coefficients A1t, A2t, . . . , ANt and B1t, B2t, . . . , BPt being sequentially adjusted at each time t so that the mean power of error signal et is minimal. Instead of carrying out the prediction on the basis of signals yt and et only according to the invention, use is also made of the real signal yt and the real error et. A linear filtering of yt using the coefficients A1t, A2t, . . . , ANt, these coefficients affecting N successive samples of the signal yt, a linear filtering of et using the coefficients B1t, B2t, . . . , BPt are performed. In addition, the quantities thus obtained are respectively weighted by two coefficients between 0 and 1 and not simultaneously zero.
141 Citations
4 Claims
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1. A coding process of the adaptive prediction differential PCM type comprising the steps of:
- forming an error signal et from the difference between a sample of signal yt to be coded and a prediction signal pt of said signal in which t is a sampling time;
quantizing said error signal et ;
coding the quantized signal;
forming a restored error signal et from one of said quantized and coded signals;
forming a restored signal yt by adding said restored error signal et to said prediction signal pt ; and
forming said prediction signal pt from said restored signals yt and et by first and second linear filtering operations;
said first operation being performed using N successive samples of yt, namely, yt, yt-1, . . . , yt-N+1, and comprising taking a sequence of N samples from a first sequence formed by said N samples of yt and from a second sequence obtained by orthogonalizing said N samples of yt, and multiplying said sequence of N samples respectively by coefficients A1t, A2t, . . . , ANt, then summing the products obtained to obtain a prediction signal pyt ;
said second operation being performed using P successive samples of et, namely, et, et-1, . . . , et-p+1, and comprising multiplying said P successive samples respectively by coefficients B1t, B2t, . . . , BPt and summing the products obtained to obtain a prediction signal pet ;
adjusting sequentially said coefficients A1t, A2t, . . . , ANt and B1t, B2t, . . . , BPt at each time t so that the mean power of said error signal et is minimized; and
carrying out at least one of the two following operations (a) and (b);(a) forming a linear filtering of said signal yt by using N successive samples of yt, namely, yt, yt-1, . . . , yt-N+1, and comprising taking a sequence of N samples from a first sequence formed by said N samples of yt and from a second sequence formed by N derivative samples obtained by orthogonalizing said N samples of yt, and multiplying said sequence of samples by N coefficients equal to the said coefficients A1t, A2t, . . . , ANt, then adding the products obtained to supply a filtered signal pyt, then forming on the basis of said signal pyt and said signal pyt previously obtained by the filtering of yt, a signal pARt equal to γ
AR pyt +(1-γ
AR)pyt, in which γ
AR is a regulatable coefficient between 0 and 1 (terminals included);(b) filtering the unquantized error signal et by multiplying P successive samples of said signal et, namely, et, et-1, . . . , et-P+1, by P coefficients equal respectively to said coefficients B1t, B2t, . . . , BPt and adding the products obtained, to supply a filtered signal pet, then forming on the basis of said signal pet and the signal pet obtained previously by filtering et a signal pMAt which is equal to γ
MA pet +(1-γ
MA)pet, 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 pARt and pMAt, then delaying one sampling time of the sum obtained, to supply said prediction signal pt. - View Dependent Claims (2)
- forming an error signal et from the difference between a sample of signal yt to be coded and a prediction signal pt of said signal in which t is a sampling time;
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3. 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 yt and a prediction signal pt in which t is a sampling time and an output supplying an error signal et, a quantizer of the error signal et, followed by a coder of the quantized signal, a circuit able to form a restored error signal et from the quantized or coded signal, an adder with two inputs receiving the restored error signal and the prediction signal pt and with an output supplying a restored signal yt and a predictor receiving the restored signals yt and et and supplying the said prediction signal pt, said predictor comprising two linear filters, the first acting on the restored signal yt and comprising N circuits for the formation of coefficients A1t, A2t, . . . , ANt, a first group of N multipliers with two inputs respectively receiving N successive samples of yt to be filtered, i.e. yt, yt-1, . . . , yt-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 pyt, the second comprising P circuits for the formation of P coefficients B1t, B2t, . . . , BPt and a second group of P multipliers with two inputs respectively receiving the P successive samples of et, i.e. et, et-1, . . . , et-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 pet, said two filters comprising means for sequentially adjusting at each time t the coefficients A1t, . . . , ANt and B1.sub. t, . . . , BPt in such a way that the mean power of the error signal et is minimal, wherein the predictor comprises means for shaping the spectrum of the quantization noise on yt (i.e. Δ
- yt =yt -yt) by arranging said spectrum in parallel with that of the restored signal yt, said means comprising;
(A) at least one of the following circuits; (a) a first circuit constituted by a filter of signal yt comprising a first group of N multipliers with two inputs respectively receiving N successive samples of yt, i.e. yt, yt-1, . . . , yt-N+1 (or derived samples) and N coefficients respectively equal to said coefficients A1t, A2t, . . . , ANt sampled in the first filter of the predictor acting on yt and an adding circuit with N inputs connected to the N multipliers of the first group and with an output supplying a filtered signal pyt and by a first algebraic circuit with two inputs, one connected to the output of the filter of yt and receiving the signal pyt and the other connected to the output of the filter of yt and receiving the signal pyt, said first algebraic circuit supplying at one output a signal pARt equal to γ
AR pyt +(1-γ
AR) pyt, 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 et comprising a second group of P multipliers with two inputs respectively receiving P successive samples of et, i.e. et, et-1, . . . , et-P+1 and P coefficients equal then respectively to said coefficients B1t, B2t, . . . , BPt sampled in the second filter of the predictor acting on et and an adder with P inputs connected to P multipliers of the second group and with an output supplying a filtered signal pet and by a second algebraic circuit with two inputs, one connected to the output of the filter of et and receiving the signal pet and the other to the output of the filter of et and receiving the signal pet, said second algebraic circuit supplying at an output a signal pMAt equal to γ
MA pet +(1-γ
MA)pet, 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 pARt +PMAt ; (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 pt. - View Dependent Claims (4)
- yt =yt -yt) by arranging said spectrum in parallel with that of the restored signal yt, said means comprising;
Specification