Low bit-rate pattern coding with recursive orthogonal decision of parameters

• US 4,724,535 A
• Filed: 04/16/1985
• Issued: 02/09/1988
• Est. Priority Date: 04/17/1984
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Ono, Shigeru
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Telesz, Jr., Andrew J.
• Application Number:
  US06/723,987
• Time in Patent Office: 1,029 Days
• Field of Search: 370/118, 375/25, 375/26, 375/34, 375/122, 358/138, 381/29, 381/31
• US Class Current: 375/241
• CPC Class Codes: G10L 19/10 the excitation function being a multipulse excitation

Abstract

Instead of an excitation pulse sequence producing circuit which is used according to prior art in calculating locations of excitation pulses and pulse amplitudes thereof, an excitation pulse sequence parameter producing circuit is used in a low bit-rate pattern coding device in recursively giving delays of the respective pulse locations to a discrete impulse response sequence to provide a system of delayed impulse responses and in transforming the delayed impulse response system into an orthogonal set of set elements. Meanwhile, the pulse locations are determined with element amplitudes or factors calculated for the respective system elements by the use of the system elements and each segment of a discrete pattern signal sequence. The pulse locations and the element amplitudes are used as parameters descriptive of the excitation pulses. Alternatively, the pulse locations are determined one at a time after quantization of each of the recursively determined element amplitudes. Preferably, the discrete impulse response sequence and the segment are weighted in consideration of auditory or like sensual effects. In a counterpart decoder, the pulse amplitudes are calculated by the use of the pulse locations and the system elements which are calculated by using the pulse locations and another parameter sequence which, in turn, is derived in the coding device from the segment in the manner in the art of multi-pulse excitation.

Claims

1. A method of coding each segment of a discrete pattern signal sequence derived from an original pattern signal into an output code sequence consisting of a first and a second code sequence, said second code sequence being equivalent to a sequence of codes representative of a predetermined number of excitation pulses, respectively, which are for use in reproducing said original pattern signal by exciting a synthesizing filter and which have pulse locations in said segment, respectively, said method comprising the steps of:

using said segment in calculating a first parameter sequence of reflection coefficients;

coding said first parameter sequence into said first code sequence;

using said first parameter sequence in calculating the discrete impulse response of said synthesizing filter;

using said segment and said discrete impulse response in recursively determining said pulse locations by recursively producing a set of delayed impulse responses with said discrete impulse responses given delays which are equal to the respective pulse locations, by recursively transforming said set of delayed impulse responses into an orthogonal set of set elements which are equal in number to said excitation pulses and for which element amplitudes are defined, respectively, and to recursively determining said element amplitudes;

using the recursively determined pulse locations and the recursively determined element amplitudes collectively as a second parameter sequence; and

coding said second parameter sequence into said second code sequence.

2. The method of coding as recited in claim 1, wherein the step of recursively determining said pulse locations includes

quantizing the recursively determined element amplitudes into quantized element amplitudes.

3. The method of coding as recited in claim 2 further including the steps of:

using said segment and said first parameter sequence in calculating a discrete segment which is weighted in consideration of a frequency characteristic of said synthesizing filter, and

calculating a discrete impulse response that is weighted in consideration of said frequency characteristic, and

using said weighted impulse response and said weighted segment in said recursive determination of pulse locations.

4. The method of coding as recited in claim 1 further including the steps of:

using said segment and said first parameter sequence in calculating a discrete segment which is weighted in consideration of a frequency characteristic of said synthesizing filter, and

calculating a discrete impulse response that is weighted in consideration of said frequency characteristic

and using said weighted impulse response and said weighted segment in said recursive determination of pulse locations.

5. A method of coding each segment of an original pattern signal into an output code sequence, said method comprising the steps of:

generating a predetermined number of signal sequences which can be used in approximating said segment by a linear sum of discrete signals given by multiplying said signal sequences by signal amplitudes defined therefor, respectively;

transforming a set of said signal sequences into an orthogonal set of set elements which are equal in number to said signal sequences and for which element amplitudes are defined, respectively;

using said segment and said orthogonal sequences in recursively determining said element amplitudes so as to minimize a difference between said segment and a linear sum of products which are given by multiplying said set elements by the recursively determined element amplitudes, respectively;

quantizing the recursively determined element amplitudes and said set elements into quantized element amplitudes and quantized system elements; and

using said quantized element amplitudes and said quantized set elements collectively as said output code sequence.

6. A method of decoding an input code sequence consisting of a first and a second code sequence into a reproduced pattern signal, said second code sequence being equivalent to a sequence of codes representative of a predetermined number of excitation pulses, respectively, which are for use in reproducing a segment of an original pattern signal as said reproduced pattern signal by exciting a synthesizing filter and each of which has a pulse instant in said segment and a pulse amplitude, said first and said second code sequences being produced by:

using said segment in calculating a first parameter sequence of reflection coefficients;

coding said first parameter sequence into said first code sequence;

using said first parameter sequence in calculating the discrete impulse response of said synthesizing filter;

using said segment and said discrete impulse response in recursively determining said pulse locations by recursively producing a set of delayed impulse responses with said discrete impulse response given delays which are equal to the respective pulse locations, by recursively transforming said set of delayed impulse responses into an orthogonal set of elements which are equal in number of said excitation pulses and for which element amplitudes are defined, respectively, and by recursively determining said element amplitudes;

using the recursively determined pulse locations and the recursively determined element amplitudes collectively as a second parameter sequence; and

coding said second parameter sequence into said second code sequence;

said method comprising the steps of;

decoding said first code sequence into a reproduction of said first parameter sequence;

using said reproduction of said first parameter sequence in calculating a reproduction of said discrete impulse response;

decoding said second code sequence into reproductions of said pulse locations and reproductions of said element amplitudes;

using said reproduction of said discrete impulse response, said reproductions of pulse locations, and said reproductions of element amplitudes in calculating calculated amplitudes which correspond to the pulse amplitudes of the respective excitation pulses; and

using said reproduction of said first parameter sequence in defining said synthesizing filter and using said reproductions of pulse locations and said calculated amplitudes in producing said reproduced pattern signal by exciting the synthesizing filter defined by said reproduction of said first parameter sequence.

7. The method of coding as recited in claim 6 further including the steps of:

using said segment and said first parameter sequence in calculating a discrete segment which is weighted in consideration of a frequency characteristic of said synthesizing filter, and

calculating a discrete impulse response that is weighted in consideration of said frequency characteristic, and

using said weighted impulse response and said weighted segment in said recursive determination of pulse locations.

8. A method of decoding an input code sequence consisting of a first and a second code sequence into a reproduced pattern signal, said second code sequence being equivalent to a sequence of codes representative of a predetermined number of excitation pulses, respectively, which are for use in reproducing a segment of an original pattern signal as said reproduced pattern signal by exciting a synthesizing filter and each of which has a pulse location in said segment and a pulse amplitude, said first and said second code sequences being produced by:

using said segment in calculating a first parameter sequence of reflection coefficients;

coding said first parameter sequence into said first code sequence;

using said first parameter sequence in calculating the discrete impulse response of said synthesizing filter;

using said segment and said discrete impulse response in recursively determining said pulse locations by recursively producing a set of delayed impulse responses with said discrete impulse response given delays, which are equal to the respective pulse locations, by recursively transforming said set of delayed impulse responses into an orthogonal set of set elements which are equal in number to said excitation pulses and for which element amplitudes are defined, respectively, and by recursively determining said element amplitudes, and by quantizing the recursively determined element amplitudes into quantized element amplitudes;

using the recursively determined pulse locations and said quantized element amplitudes collectively as a second parameter sequence; and

coding said second parameter sequence into said second code sequence;

said method comprising the steps of;

decoding said first code sequence into a reproduction of said first parameter sequence;

using said reproduction of first parameter sequence in calculating a reproduction of said discrete impulse response;

decoding said second code sequence into reproductions of said pulse locations and reproductions of said element amplitudes;

using said reproduction of said discrete impulse response, said reproductions of said pulse locations, and said reproductions of element amplitudes in calculating calculated amplitudes which correspond to the pulse amplitudes of the respective excitation pulses; and

using said reproduction of said first parameter sequence in defining said synthesizing filter and using said reproductions of pulse locations and said calculated amplitudes in producing said reproduced pattern signal by exciting the synthesizing filter defined by said reproduction of said first parameter sequence.

9. The method of coding as recited in claim 8 wherein:

the step of recursively determining said pulse locations includes quantizing the recursively determined element amplitude into quantized element amplitudes; and

the method includes the further steps of;

using said segment and said first parameter sequence in calculating a discrete segment which is weighted in consideration of a frequency characteristic of said synthesizing filter, and

calculating a discrete impulse response that is weighted in consideration of said frequency characteristic, and

using said weighted impulse response and said weighted segment in said recursive determination of pulse locations.

10. A method of decoding an input code sequence into a reproduced pattern signal, said input code sequence being produced by coding each segment of an original pattern signal into an output code sequence by:

generating a predetermined number of signal sequences which can be used in approximating said segment by a linear sum of discrete signals given by multiplying said signal sequences by signal amplitudes defined therefor, respectively;

transforming a set of said signal sequences into an orthogonal set of set elements which are equal in number to said signal sequences and for which element amplitudes are defined, respectively;

using said segment and said set of orthogonal sequences in recursively determining said element amplitudes so as to minimize a difference between said segment and a linear sum of products which are given by multiplying said set elements by the recursively determined element amplitudes, respectively;

quantizing the recursively determining element amplitudes and said set elements into quantized element amplitudes and quantized set elements; and

using said quantized element amplitudes and said quantized set elements collectively as said output code sequence;

said method comprising the steps of;

decoding said quantized set elements into reproductions of said set elements;

decoding said quantized element amplitudes into reproductions of said element amplitudes; and

using said reproductions of system elements and said reproductions of element amplitudes in producing a reproduction of said linear sum of products as said reproduced pattern signal.

11. A device for coding each segment of an original pattern signal into an output code sequence, said device comprising:

means for generating a predetermined number of signal sequences which can be used in approximating said segment by a linear sum of discrete signals given by multiplying said signal sequences by signal amplitudes defined therefor, respectively;

means for transforming a set of said signal sequences into an orthogonal set of set elements which are equal in number to said signal sequences and for which element amplitudes are defined, respectively;

means responsive to said segment and said orthogonal set for recursively determining said element amplitudes so as to minimize a difference between said segment and a linear sum of products which are given by multiplying said set elements by the recursively determined element amplitudes, respectively; and

means for producing said output code sequence by quantizing the recursively determined element amplitudes and said set elements into quantized element amplitudes and quantized set elements.