Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1999-12-22
2002-06-18
Banks-Harold, Marsha D. (Department: 2654)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S223000
Reexamination Certificate
active
06408268
ABSTRACT:
This application is the national phase under 35 U.S.C. § of prior PCT International Application No. PCT/JP97/03366 which has an International filing date of Sep. 24, 1997 which designated the United States of America.
TECHNICAL FIELD
This invention relates to a method and apparatus for speech encoding, which performs compression-encoding for a speech signal to be a digital signal, and speech decoding, which performs expansion-decoding for the digital signal to be the speech signal. In addition, this invention relates to a method and apparatus for speech coding/decoding in which the speech encoding and the speech decoding are combined.
BACKGROUND ART
In many conventional speech coding/decoding apparatuses, an input speech is divided into spectrum-envelope information and an excitation signal. Then, the excitation signal is encoded per frame, and the encoded excitation signal is decoded to generate an output speech.
The spectrum-envelope information represents a general figure of an amplitude (power) spectrum of speech signal. The excitation signal is an energy source for generating speech. In a speech coding process and a speech synthesis, the excitation signal is represented by a form using a periodic pattern or a periodic series of pulses to be approximately shown. Many improvements have been performed especially for the method of excitation signal coding/decoding in order to enhance the quality of coding/decoding. A speech coding/decoding apparatus applying “celp” (code-excited linear predictive coding) is known as the most typical speech coding/decoding apparatus.
FIG. 13
shows a whole configuration of the conventional speech coding/decoding apparatus applying celp. In
FIG. 13
, a coding unit
1
, decoding unit
2
, multiplexing unit
3
, separating unit
4
, input speech
5
, code
6
and an output speech
7
are shown. The coding unit
1
is composed of a linear prediction analyzing unit
8
, linear predictive coefficient coding unit
9
, adaptive excitation coding unit
10
, stochastic excitation coding unit
11
and a gain coding unit
12
. The decoding unit
2
is composed of a linear predictive coefficient decoding unit
13
, synthesis filter
14
, adaptive excitation decoding unit
15
, stochastic excitation decoding unit
16
and a gain decoding unit
17
.
A speech of around 5 to 50 ms long is defined as a frame in the conventional speech coding/decoding apparatus. The speech in the frame is divided into spectrum-envelope information and an excitation signal in order to be encoded.
The operation of the conventional speech coding/decoding apparatus will now be described. First, in the coding unit
1
, the linear prediction analyzing unit
8
analyzes the input speech
5
, and extracts a linear predictive coefficient which is the spectrum-envelope information of the speech. The linear predictive coefficient coding unit
9
encodes the linear predictive coefficient, and outputs the encoded code to the multiplexing unit
3
as a coded linear predictive coefficient
18
for excitation signal encoding.
Referring to
FIGS. 20
,
21
and
22
, the excitation signal encoding is now explained. As shown in
FIG. 20
, a plurality of old excitation signals (that is, Sold excitation signals) is stored as adaptive excitations
113
corresponding to adaptive excitation codes
111
in an adaptive excitation codebook
110
of the adaptive excitation coding unit
10
. A time series vector
114
is generated by periodically repeating the adaptive excitation
113
, that is the old excitation signal, corresponding to each adaptive excitation code
111
. Then, a temporary synthetic signal
116
is generated by multiplying each time series vector
114
by an appropriate gain “g” and filtering the multiplied time series vector
114
by using a synthesis filter
115
in which the coded linear predictive coefficient
18
is used. An error signal
118
is obtained based on a differential between the temporary synthetic signal
116
and the input speech
5
to calculate the distance between the temporary synthetic signal
116
and the input speech
5
. This process is repeated S times by using each adaptive excitation
113
. Then, the adaptive excitation code
111
which makes the distance shortest is selected. The time series vector
114
corresponding to the selected adaptive excitation code
111
is output as the adaptive excitation
113
, and one of the error signals
118
corresponding to the selected adaptive excitation code
111
is also output.
As shown in
FIG. 21
, a plurality of stochastic excitations
133
(that is, T stochastic excitations) corresponding to stochastic excitation codes
131
is stored in a stochastic excitation codebook
130
of the stochastic excitation coding unit
11
. A temporary synthetic signal
136
is generated by multiplying each stochastic excitation
133
by the appropriate gain “g” and filtering the multiplied stochastic excitation
133
by using a synthesis filter
135
in which the coded linear predictive coefficient
18
is used. The distance between the temporary synthetic signal
136
and the error signal
118
is calculated. This process is repeated T times by using each stochastic excitation
133
. Then, the stochastic excitation code
131
which makes the distance shortest is selected and the stochastic excitation
133
corresponding to the selected stochastic excitation code
131
is also output.
As shown in
FIG. 22
, a plurality of gain groups (that is, U gain groups) corresponding to gain codes
151
is stored in a gain codebook
150
of the gain coding unit
12
. A gain vector
154
(g
1
, g
2
) corresponding to each gain code
151
is generated. A temporary synthetic signal
156
is generated by multiplying the adaptive excitation
113
(time series vector
114
) by the element g
1
of each gain vector
154
with using a multiplier
166
, multiplying the stochastic excitation
133
by the element g
2
of each gain vector
154
with using a multiplier
167
, adding the multiplied values with using an adder
968
, and filtering the added value by using a synthesis filter in which the coded linear predictive coefficient
18
is used. The distance between the temporary synthetic signal
156
and the input speech
5
is calculated. This process is repeated U times by using each gain. Then, the gain code
151
which makes the distance shortest is selected. An excitation signal
163
is generated by multiplying the adaptive excitation
113
by the element g
1
of the gain vector
154
corresponding to the selected gain code
151
, multiplying the stochastic excitation
133
by the element g
2
of the gain vector
154
corresponding to the selected gain code
151
, and adding the multiplied values. The adaptive excitation coding unit
10
updates the adaptive excitation codebook
110
by using the excitation signal
163
.
The multiplexing unit
3
multiplexes the coded linear predictive coefficient
18
, adaptive excitation code
111
, stochastic excitation code
131
and the gain code
151
and outputs the multiplexed value as the code
6
. The separating unit
4
separates the code
6
into the coded linear predictive coefficient
18
, adaptive excitation code
111
, stochastic excitation code
131
and the gain code
151
.
In the decoding unit
2
, the linear predictive coefficient decoding unit
13
decodes a linear predictive coefficient out of the coded linear predictive coefficient
18
and sets the decoded coefficient as a coefficient of the synthesis filter
14
. The adaptive excitation decoding unit
15
stores old excitation signals in an adaptive excitation codebook, and outputs a time series vector
128
made by periodically repeating plural old excitation signals corresponding to an adaptive excitation code. The stochastic excitation decoding unit
16
stores plural stochastic excitations in a stochastic excitation codebook, and outputs a time series vector
148
corresponding to a stochastic excitation code. The gain decoding unit
17
stores plural gain groups in a gain codebook and outputs a gain vector
168
corresponding to a
Banks-Harold Marsha D.
Lerner Martin
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Voice encoder, voice decoder, voice encoder/decoder, voice... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Voice encoder, voice decoder, voice encoder/decoder, voice..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Voice encoder, voice decoder, voice encoder/decoder, voice... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2920107