Linear predictive speech coding arrangement

• US 4,847,906 A
• Filed: 03/28/1986
• Issued: 07/11/1989
• Est. Priority Date: 03/28/1986
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.), Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Inventors: Ackenhusen, John G.
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): Lynt, Christopher H.
• Application Number:
  US07/845,447
• Time in Patent Office: 1,201 Days
• Field of Search: 381/41, 381/46 MS, 381/36, 381/37 MS, 364/513.5 MS
• US Class Current: 704/217
• CPC Class Codes: G10L 19/04 using predictive techniques

Abstract

A speech analyzer is adapted to produce speech parameter signals from a Pth order autocorrelation analysis of a speech pattern in a digital signal processor. The analyzer includes a plurality of memories of predetermined arrangement to store feature vector signals used in the analysis, a single set of coded signals for controlling the analysis, and a memory address processor for addressing the feature vector signal memories. In each iteration of the analysis, at least one speech parameter signal is produced by the digital signal processor responsive to the same set of control signals and the feature vector memory addressing signals.

Claims

1. A method of speech analysis, of the type comprising the steps:

receiving successive time frame interval portions of a speech pattern;

generating a set of autocorrelation signals R(0), R(1), . . . , R(P) corresponding to the present time frame interval speech pattern portion in response to the present time frame interval portion of said speech pattern; and

generating a set of linear predictive parameter signals for said present time frame interval in response to said autocorrelation signal set;

said linear predictive parameter signal set generating step comprising;

employing Durbin'"'"'s recursion, as follows;

for successive iterations i=1, 2, . . . , P, generating signals ##EQU19## where j is a subordinate index varying from 1 to i-1 within each iteration, and α

_j.sup.(i-1) is an intermediate signal initially generated from a initial reflection coefficient k, where k=s_i /E.sup.(i-1) and e.sup.(i-1) is a residual energy signal from the previous iteration which intermediate signal is to be iteratively developed into a linear predictive coefficient α

_j =α

_j.sup.(P) and ##EQU20## said method being particularly characterized in that the generating step includes generating signals for appended calculations to make each portion of each iteration repetitive of a set of arithmetic operations, so that j varies from P to 1 in each iteration, the generating step (as in FIG.

     2) including storing the autocorrelation signals for successive access for each change of the value j from P to 1 for the first signal s_i ;

storing (as in FIG.

     3) the intermediate values in the order of generation in the previous iteration and continuing through appended values equal in number to P minus the i value for said previous iteration but having P appended values equal to zero in sequence from the first value and in the opposite order, the intermediate values being sequentially accessed in the order of generation for the generation of the first term of the second signal and being sequentially accessed in the inverse order of generation for the generation of the second term of the second signal for values of j from P to 1 in each iteration;

said storing step including replacing the stored intermediate values with new values for the next iteration involving the next higher value of i in like order without affecting (P-i) nearest appended values preceding the first generated value for the previous iteration, where i is the i value of the previous iteration;

and separately accessing (as in FIG.

     2) the values of the intermediate signals in the order of generation in the previous iteration and continuing through appended values equal in number to P minus the i value for said previous iteration, said appended values being appropriate for successive access for each change of the value j from P to 1 in each iteration for the generation of the first signal s_i, the separately accessing step including replacing said stored intermediate values with new values in the order of generation after each completion iteration for a particular value of i, so that one less appended value is stored at the start of each new iteration.

2. A method of the type claimed in claim 1,

said method being further characterized in that

the first intermediate value signal storing step comprises storing, as the appended values, the values 1, 0, 0, . . . 0, where the zeros number P+1-i.

3. A method of the type claimed in claim 1 or claim 2,

said method being further characterized in that

the step of generating the first and second signals includes the steps of temporarily storing (as in section 310 of FIG. 3) the second signal values as j progresses from P to 1.