tan-1

US006115685A

Ulllted States Patent [19]

[11] Patent Number:

6,115,685

Inoue et al.

[45]

Sep. 5, 2000

[54]

PHASE DETECTION APPARATUS AND METHOD, AND AUDIO CODING

Date of Patent:

[56]

References Cited

APPARATUS AND METHOD

U.S. PATENT DOCUMENTS 4,065,665

[75]

Inventors: Akira Inoue, Tokyo; Masayuki Nishiguchi, KanagaWa, both of Japan

5,381,512 5,727,119

[73] Assignee: Sony Corporation, Tokyo, Japan

Attorney, Agent, or Firm—Jay H. Maioli

_

_

_

_

[JP]

cycle is cutout of an input signal Waveform and then that

Japan ............................. .. P10-019963

Int. Cl.7 ........................... .. G10L 11/04; G10L 19/04 U-S. Cl. ........................ ..

Cutout One-Pitch Cycle is dimension Converted into

2k-sample data. The data conversion is performed on respec ?ve higher harmonic Components Ofthe input Signal accord [O a real part and an imaginary part of the Orthogonal data

704/220 [58]

ABSTRACT

Phase detection apparatus and method, wherein a one-pitch

Forelgn Apphcatlon Pnonty Data

Jan. 30, 1998

[51]

[57]

Jan. 26, 1999 _

[30]

Rietsch .................................... .. 702/72

1/1995 Holton etal. ......................... .. 704/232 3/1998 Davidson et a1. .................... .. 704/203

tEExjgiyjggazéilRlégspeth

[21] Appl. No.: 09/236,500 [22] Filed:

12/1977

that has been converted.

Field of Search ................................... .. 704/205, 207,

704/219, 220

18 Claims, 10 Drawing Sheets

CUT OUT ONE-PITCH WAVEFORM SIGNAL STARTING AT ANALYSIS POINT

DIMENSION CONVERSION

l 1 tan-1

U.S. Patent

Sep. 5,2000

Sheet 1 0f 10

6,115,685

0&lmJ?4 m: + m \ F2 _

M25x9M:mP5Em3sw H\zNEmo_.2~;zhmZ

mwwe“: zsmEuom1m: kuI :052 mm m

\ m h

.MHWmw?2JEv

5 m258.1mm“;5

MM 753M&\0.1 5

m irmmwozbPSv9?“mw?a mm3c|o.zwE0m?2u6:wmzo50_.Emau5o_Y

the m'th_harmomcs Com‘ ponent at time n (nlénénz) has an amplitude that can be obtained as folloWs using linear interpolation of the ampli

synthesis backWard from time n2, so that these Wveforms are Subjected to Overlap add

tude data at time n1 and n2.

V1 (n) : ZAlmcOS(ma)l(n_nl)+¢lm)

Suppose that the frequency change of the m-th harmonics

_

(2Q)

_

_

Component between the time H1 and n2 is (linear 25 According to the phase detection apparatus having the component)+(?xed ?uctuaton) as Shown below aforementioned con?guration, it is possible to rapidly detect a phase of a desired harmonics component using a prede

tectded pitch frequency by Way of the FFT processing and the linear interpolation. This enables to realiZe a Waveform

@mm) = "1131

3O reproduction (regeneration) in an audio signal sinusoidal encoding or an audio encoding using sinusoidal encoding on Here, the m-th harmonics component at time n has a phase

the LPC residue of the audio Signal. _

6m(n)(rad) which can be expressed by Expression (12) By calculation of the Expression (12), it is possible to obtain Expression (13) below

3

0mm) = f"@m(§)d§+ ¢1m

_

_

I It should be noted that the present ‘invention is not to be hhhted t0 the aforethehtlehed embedhheht- Ih the eehhgu' ration of FIG. 1, the respective components are described as hardWard, but it is also possible to realiZe these components by a softWare program using a so-called DSP (digital signal

(11)

processor).

(12)

phase detection apparatus and method according to the

"1

As is clear from the aforementioned explanation, in the

= f" ("15,1 "rs “?ags-"1 + Aampgarqhm n1

L

L n _ n1 )2

=m5)1("—"1)+m(5’2-5’1)

2L

40 present invention, one-pitch cycle is cut out from an input signal Waveform based on an audio signal on a time axis, and

+M’mL+¢1m (13)

samples of the cut out one-pitch cycle are subjected to dimension conversion into a 2k-sample data, Which is then subjected to an orthogonal conversion such as 2k-point FFT. the m-th harmonics at time n2 has a phase ¢2m(rad) Which 45 A real part and an imaginary part of the orthogonally can be expressed by Expression (15) beloW. converted data are used to detect a phase information of each

higher harmonics component of the input signal, thus ¢2m : gmmz)

(14)

enabling to easily detect the phase information of the

original Waveform, improving the Waveform reproductivity. : m?bi +5)2)L + M) L+ ¢

2

m

(15)

50

1'"

Using a predetected pitch for the dimension conversion

and the FFT (fast Fourier transform), it is possible to rapidly

detect the phase of each harmonics (higher harmoncs) component. When this is applied to sinusoidal encoding, it is possible to enhance the Waveform reproductivity. For

Cohseqhehtly, each harmonic COIhPOheht has afrequency

Change Aw,” (rad/sample) expressed by EXPTeSSiOII (16)

example, it is possible to prevent the synthesiZe audio from 55 becoming unnatural.

~

(¢lm _¢2m)

"1(5), + (32)

(16)

What is claimed is:

Awm : T _ f

1. A phase detection apparatus comprising: Waveform cut-out means for cutting out on a time axis a

one-pitch cycle of an input signal Waveform derived For the m-th harmonics component, phase (1)1," and (1)2," at 60 thhe h1 ahd h2 are giVeh~Aee0rdihg1Y> it is Possible Ohtaih

the ?xed ?uctuation Arum of the frequency change from the Expresson (16) and the phase 6m at time n from the

Said Cut-Out One-pitch cycle of the input signal Wave form into 2k-sample data: Wherein k is an integer;

EXpression (13)- Thus, time WaVefOrIIl Wm(h) by the IIl-th harmonics component can be expressed as folloWs.

Wm(n)=Am(n)cos(6m(n))(n1énénz)

orthogonal conversion means for performing orthogonal 65

(17)

from an audio signal; dimension conversion means for dimension-converting

conversion on said 2k-sample data Which has been

dimension-converted by said dimension conversion means; and

6,115,685 11

12

phase detection means for detecting phase information of

orthogonal conversion means for performing orthogonal

respective higher harmonics components of said input

conversion on said 2k-sample data Which has been dimension-converted by said dimension conversion

signal Waveform according to a real part and an imagi

nary part of orthogonal data from said orthogonal

means; and

conversion means.

phase detection means for detecting phase information of

2. The phase detection apparatus as claimed in claim 1, Wherein said input signal Waveform is an audio signal

respective higher harmonics components of said input signal for said sinusoidal synthesis according to a real part and an imaginary part of orthogonal data from said

Waveform. 3. The phase detection apparatus as claimed in claim 1,

Wherein said input signal Waveform is a signal Waveform of a short-term prediction residue of an audio signal. 4. The phase detection apparatus as claimed in claim 1, Wherein said dimension conversion means includes means

for performing dimension conversion into the 2k-sample data by oversampling and linear interpolation of said cut-out one-pitch cycle of the input signal Waveform from said

15

Waveform cut-out means.

5. The phase detection apparatus as claimed in claim 1, Wherein said orthogonal conversion means comprises a fast

orthogonal conversion means. 11. The audio coding apparatus as claimed in claim 10, Wherein said input signal Waveform is an audio signal Waveform. 12. The audio coding apparatus as claimed in claim 10, Wherein said input signal Waveform is a short-term predic tion signal of an audio signal Waveform. 13. The audio coding apparatus as claimed in claim 10, Wherein said dimension conversion means includes means

Fourier transform circuit for performing a 2k-point fast Fourier transform processing on said 2k-sample data from

for performing dimension conversion into the 2k-sample data by oversampling and linear interpolation of said cut-out one-pitch cycle of the input signal Waveform from said

said dimension conversion means.

Waveform cut-out means.

6. The phase detection apparatus as claimed in claim 1,

14. The audio coding apparatus as claimed in claim 10, Wherein said orthogonal conversion means comprises a fast

Wherein said phase detection means includes means for

obtaining a phase value for each said higher harmonics component by calculating an inverse tangent (tan-1) using a real part and an imaginary part of the orthogonal data from

25

dimension conversion means.

said orthogonal conversion means.

15. The audio coding apparatus as claimed in claim 10,

7. A phase detection method comprising:

Wherein said phase detection means includes means for

a Waveform cut-out step for cutting out on a time aXis a

obtaining a phase value for each higher harmonics compo nent by calculating an inverse tangent (tan_1) using a real part and an imaginary part of the orthogonal data from said

one-pitch cycle of an input signal Waveform derived from an audio signal;

a dimension conversion step for dimension-converting said cut-out one-pitch cycle of the input signal Wave form into 2k-sample data: Wherein k is an integer;

orthogonal conversion means. 35

obtaining a pitch for each of said blocks, and performing

conversion on said 2k-sample data Which has been dimension-converted in said dimension conversion

sinusoidal Wave analysis-by-synthesis encoding on each of

said blocks, said method comprising:

step; and a phase detection step for detecting a phase information of

a Waveform cut-out step for cutting out on the time aXis

a one-pitch cycle of said input signal Waveform;

respective higher harmonics components of said input

a dimension conversion step for dimension-converting

signal according to a real part and an imaginary part of

orthogonal data from said orthogonal conversion step. 45

sion conversion into the 2k-sample data by oversampling and linear interpolation of said cut-out one-pitch cycle of the input signal Waveform data from said Waveform cut-out

step; and a phase detection step for detecting a phase information of

9. The phase detection method as claimed in claim 7, Wherein said phase detection step obtains a phase value for each higher harmonics component by calculating an inverse tangent (tan_1) using a real part and an imaginary part of the

respective higher harmonics components of said input signal for said sinusoidal synthesis according to a real part and an imaginary part of orthogonal data from said 55

Waveform based on an audio signal into blocks on a time

orthogonal conversion step. 17. The audio coding method as claimed in claim 16, Wherein said dimension conversion step performs a dimen

sion conversion into the 2k-sample data by oversampling and linear interpolation of said cut-out one-pitch cycle of the input signal Waveform from said Waveform cut-out step.

axis, obtaining a pitch for each of said blocks, and perform ing sinusoidal Wave analysis-by-synthesis encoding on each

of said blocks, said apparatus comprising:

18. The audio coding method as claimed in claim 16, Wherein said phase detection step obtains a phase value for each higher harmonics component by calculating an inverse tangent (tan_1) using a real part and an imaginary part of the

Waveform cut-out means for cutting out on the time aXis

a one-pitch cycle of said input signal Waveform; dimension conversion means for dimension-converting

said cut-out one-pitch cycle of the input signal Wave form into 2k-sample data: Wherein k is an integer equal

said cut-out one-pitch cycle of said input signal Wave form into 2k-sample data: Wherein k is an integer; an orthogonal conversion step for performing orthogonal conversion on said 2k-sample data Which has been dimension-converted in said dimension conversion

step.

orthogonal data from said orthogonal conversion step. 10. An audio coding apparatus for dividing an input signal

16. An audio coding method for dividing an input signal based on an audio signal into blocks on a time axis,

an orthogonal conversion step for performing orthogonal

8. The phase detection method as claimed in claim 7, Wherein said dimension conversion step performs a dimen

Fourier transform circuit for performing 2k-point fast Fou rier transform processing on said 2k-sample data from said

65

orthogonal data from said orthogonal conversion step.

to or greater than a number of samples of said one pitch

cycle;

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