Encoder apparatus and decoder apparatus

• US 20060251178A1
• Filed: 09/15/2004
• Published: 11/09/2006
• Est. Priority Date: 09/16/2003
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Oshikiri, Masahiro
• Granted Patent: US 7,844,451 B2
• Time in Patent Office: Days
• US Class Current: 375/242
• CPC Class Codes: G10L 19/083 the excitation function being an excitation gain G10L25/90 takes precedence
• CPC Class Codes: H04B 1/667 using a division in frequency subbands for TV signals H04N19/63

Abstract

A coding apparatus capable of coding a spectrum at a low bit rate and with high quality without producing any disturbance in a harmonic structure of the spectrum. In this apparatus, internal state setting section (106) sets an internal state of filtering section (107) using first spectrum S1(k). Pitch coefficient setting section (109) outputs pitch coefficient T by gradually changing it. Filtering section (107) calculates estimated value S′2(k) of second spectrum S2(k) based on pitch coefficient T. Search section (108) calculates the degree of similarity between S2(k) and S′2(k). At this time, pitch coefficient T′ corresponding to the maximum calculated degree of similarity is given to filter coefficient calculation section (110). Filter coefficient calculation section (110) determines filter coefficient β_i using this pitch coefficient T′.

Claims

1-15. -15. (canceled)

16. A spectrum coding apparatus that encodes a spectrum including a first band and a second band, comprising:

an acquisition section that acquires information about a spectrum similar to a spectrum of said second band from a spectrum of said first band based on a harmonic structure; and

a coding section that encodes said information instead of the spectrum of said second band.

17. The spectrum coding apparatus according to claim 16, wherein said information is shape information about a spectrum similar to the spectrum of said second band.

18. The spectrum coding apparatus according to claim 16, wherein said acquisition section generates an estimated spectrum similar to the spectrum of said second band based on a harmonic structure of said spectrum and acquires information about said estimated spectrum.

19. A coding apparatus comprising:

an acquisition section that acquires a spectrum having a low frequency band and a high frequency band;

a generation section that generates a parameter indicating a degree of similarity between said spectrum of the low frequency band and said spectrum of the high frequency band based on a harmonic structure of said spectrum; and

a coding section that encodes said parameter indicating the degree of similarity instead of said spectrum of the high frequency band.

20. The coding apparatus according to claim 19, wherein said generation section comprises:

a spectrum generation section that generates a spectrum similar to said spectrum of the high frequency band based on said spectrum of the low frequency band separated by an integer multiple of a pitch of said harmonic structure from said spectrum of the high frequency band; and

an output section that outputs a parameter indicating a characteristic of said similar spectrum as said parameter indicating the degree of similarity.

21. The coding apparatus according to claim 20, wherein said spectrum generation section generates said similar spectrum using a filter,

said filter comprises said spectrum of the low frequency band separated by an integer multiple of a pitch of said harmonic structure from said spectrum of the high frequency band as an internal state, and

said output section outputs a filter coefficient of said filter as a parameter indicating said degree of similarity.

22. The coding apparatus according to claim 19, wherein said coding section also encodes envelope information about said spectrum of the high frequency band.

23. The coding apparatus according to claim 19, wherein said coding section also encodes information about a power ratio between said spectrum of the low frequency band and said spectrum of the high frequency band.

24. The coding apparatus according to claim 19, wherein said generation section comprises:

an estimation section that estimates said spectrum of the high frequency band using a filter having said spectrum of the low frequency band as an internal state; and

an output section that outputs a parameter indicating a characteristic of said filter,

wherein a filter function of said filter is expressed by the following equation, and

said estimation section performs said estimation using a zero input response of said filter.

$P<br><br>\left(z\right)=\frac{1}{1-\underset{i=-M}{\overset{M}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\beta <br><br>}}_i<br><br>z^{-T+i}}$

where,

P(z);

Filter function

z;

z conversion variable

2M+1;

Order of filter

β

;

Weighting factor

T;

Pitch coefficient

25. The coding apparatus according to claim 24, wherein M=0 and β

0=1 in said filter function.

26. The coding apparatus according to claim 19, wherein said spectrum of the low frequency band is obtained from a signal decoded after being coded in a lower layer through hierarchical coding.

27. A communication terminal apparatus comprising the coding apparatus according to claim 19.

28. A scalable coding apparatus that encodes a voice signal or audio signal separated into a low frequency band and high frequency band, comprising:

a first coding section that encodes a low-frequency band signal of said voice signal or said audio signal; and

a second coding section that encodes a high-frequency band signal of said voice signal or said audio signal using said low-frequency band signal,

wherein said second coding section comprises;

a first spectrum generation section that performs frequency domain conversion on said low-frequency band signal and generates a spectrum of the low frequency band;

a second spectrum generation section that performs frequency domain conversion on said voice signal or said audio signal and generates a spectrum having the low frequency band and high frequency band; and

the coding apparatus of claim 19 wherein said acquisition section acquires spectra generated by said first and second spectrum generation sections.

29. A communication terminal apparatus comprising the scalable coding apparatus according to claim 28.

30. A decoding apparatus comprising:

a spectrum acquisition section that acquires a spectrum of a low frequency band out of a spectrum having a low frequency band and high frequency band;

a parameter acquisition section that acquires a parameter indicating a degree of similarity between said spectrum of the low frequency band and said spectrum of the high frequency band; and

a decoding section that decodes said spectrum of the low frequency band and said spectrum of the high frequency band using said spectrum of the low frequency band and said parameter.

31. The decoding apparatus according to claim 30, further comprising an envelope information acquisition section that acquires envelope information of said spectrum of the high frequency band,

wherein said decoding section performs said decoding using also said envelope information.

32. The decoding apparatus according to claim 30, wherein said decoding section comprises an estimation section that includes said spectrum of the low frequency band as an internal state and estimates said spectrum of the high frequency band using a filter having said parameter as a filter characteristic,

a filter function of said filter is expressed by the following equation, and

said estimation section performs said estimation using a zero input response of said filter.

$P$

(z)=11-∑

i=-MM⁢

 

⁢

β

i⁢

z-T+i

where,

P(z);

Filter function

z;

z conversion variable

2M+1;

Order of filter

β

;

Weighting factor

T;

Pitch coefficient

33. The decoding apparatus according to claim 32, wherein M=0 and β

0=1 in said filter function.

34. The decoding apparatus according to claim 30, wherein said spectrum of the low frequency band is generated from a signal decoded in a lower layer through hierarchical coding.

35. A communication terminal apparatus comprising the decoding apparatus according to claim 30.

36. A coding method comprising the steps of:

acquiring a spectrum having a low frequency band and a high frequency band;

generating a parameter indicating a degree of similarity between said spectrum of the low frequency band and said spectrum of the high-frequency band based on a harmonic structure of said spectrum; and

encoding said parameter indicating the similarity instead of said spectrum of the high frequency band.

37. A decoding method comprising the steps of:

acquiring a spectrum having a low frequency band out of a spectrum having a low frequency band and high-frequency band;

acquiring a parameter indicating a degree of similarity between said spectrum of the low frequency band and said spectrum of the high frequency band; and

decoding said spectrum of the low frequency band and said spectrum of the high frequency band using said spectrum of the low frequency band and said parameter.