Coded data generation or conversion – Digital code to digital code converters – Adaptive coding
Reexamination Certificate
2000-11-15
2002-07-16
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
Adaptive coding
C382S232000, C382S250000, C382S248000
Reexamination Certificate
active
06420979
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for compressing of image signals and decompressing of image signals and to an apparatus to implement of image signals compressing of image signals and decompressing of image signals.
The present application claims the Convention Priority of Japanese Patent Application No. Hei11-326188 filed on Nov. 16, 1999, which is hereby incorporated by reference.
2. Description of the Related Art
Conventionally, when a digitized image is transmitted, since an amount of image information is enormous, the image information is compressed prior to its transmission. As one of methods for compressing image information, international standard coding systems called MPEG (Moving Picture Experts Group) and JPEG (Joint Photographic Experts Group) are known. In the international standard coding systems, input image data is compressed by DCT (Discrete Cosine Transformation) and compressed image data is returned to its original image data by IDCT (Inverse Discrete Cosine Transformation).
The DCT used in the international standard coding systems is performed in accordance with the following equation (17) provided for in International Standard (STD•IEC 61834-2-ENGL 1, 998) 8-8 DTC, which prescribes the international standard coding systems. The IDCT used in the international standard coding systems is performed in accordance with the following equation (18) provided for in the International Standard (STD•IEC 61834-2-ENGL 1, 998) 8-8 IDCT, which also prescribes the international standard coding systems.
F
(
h
,
v
)
=
C
(
v
)
C
(
h
)
∑
y
=
0
7
∑
x
=
0
7
{
f
(
x
,
y
)
cos
α
}
cos
β
where
C
(
h
)
=
1
2
2
(
h
=
0
)
,
C
(
h
)
=
1
2
(
h
=
1
,
2
,
…
,
7
)
C
(
v
)
=
1
2
2
(
v
=
0
)
,
C
(
v
)
=
1
2
(
v
=
1
,
2
,
…
,
7
)
α
≡
π
v
(
2
y
+
1
)
16
,
β
≡
π
h
(
2
x
+
1
)
16
(
17
)
f
(
x
,
y
)
=
∑
v
=
0
7
∑
h
=
0
7
{
C
(
v
)
C
(
h
)
F
(
h
,
v
)
cos
α
·
cos
β
}
where
C
(
h
)
=
1
2
2
(
h
=
0
)
,
C
(
h
)
=
1
2
(
h
=
1
,
2
,
…
,
7
)
C
(
v
)
=
1
2
2
(
v
=
0
)
,
C
(
v
)
=
1
2
(
h
=
1
,
2
,
…
,
7
)
α
≡
π
v
(
2
y
+
1
)
16
,
β
≡
π
h
(
2
x
+
1
)
16
.
(
18
)
An example of an 8-8 DCT device (called a “first technology” in this application) is disclosed in the Japanese Patent Application Laid-open No. Hei5-181896, in which the 8-8 DCT is performed on every block composed of “8×8” picture element data constituting image data, which is constructed of a product obtained by multiplying eight pieces of picture element data arranged in a transverse direction by eight pieces of picture element data arranged in a longitudinal direction, in accordance with following equation (19) and equation (20).
[
F
0
F
4
F
2
F
6
]
=
[
a
0
+
a
1
+
a
3
+
a
2
0
0
a
0
-
a
1
+
a
3
-
a
2
0
0
0
a
0
-
a
3
a
1
-
a
2
0
-
a
1
-
a
2
a
0
-
a
3
]
[
P
3
P
5
P
1
]
[
F
1
F
3
F
5
F
7
]
=
[
a
4
a
5
a
6
a
7
-
a
6
a
4
-
a
7
-
a
5
-
a
5
a
7
a
4
a
6
a
7
a
6
-
a
5
a
4
]
[
P
6
P
4
P
2
P
0
]
}
(
19
)
1
2
[
f
0
+
f
4
f
1
+
f
5
f
2
+
f
6
f
3
+
f
7
]
=
[
a
0
+
a
3
a
2
a
1
a
0
-
a
3
-
a
1
a
2
a
0
-
a
3
a
1
-
a
2
a
0
+
a
3
-
a
2
-
a
1
]
[
P
3
P
5
P
1
]
1
2
[
f
0
-
f
4
f
1
-
f
5
f
2
-
f
6
f
3
-
f
7
]
=
[
a
5
a
7
-
a
6
-
a
4
a
6
a
5
a
4
-
a
7
-
a
7
-
a
4
a
5
-
a
6
a
4
-
a
6
-
a
7
a
5
]
[
P
6
P
4
P
2
P
0
]
}
(
20
)
In the 8-8 DCT devices, the 8-8 DCT and 8-8 IDCT are performed by arithmetic operations according to a determinant equation (19) and determinant equation (20) derived from the equation (17) and the equation (18).
The first technology disclosed in the above Japanese Patent Application Laid-open No. Hei5-181896 includes two 8-8 DCT devices. One of the two 8-8 DCT, which performs the 8-8 DCT by arithmetic operations according to the determinant equation (19), is composed of eight selecting circuits adapted to select one piece of input data out of 8 pieces of input data (a
0
to a
7
), seven fixed coefficient multipliers connected to the selecting circuits and adapted to multiply each of selected signals output from the selecting circuits by a different coefficient and 5 types of adding/subtracting units connected to outputs of the fixed coefficient multipliers and adapted to perform adding and subtracting operations to each of output signals from the fixed coefficient multipliers in a variety of differently combined ways and is so configured that three types of the adding/subtracting units out of the five types of the adding/subtracting units are used for the cosine transformation and the remaining two types of the adding/subtracting units for the inverse cosine transformation and that eight cosine transformation coefficients are obtained by switching, four times, the way of selecting data in the selecting circuits and by switching, four times, the calculating way from the addition to subtraction or vice versa in the adding and subtracting units. However, input data (a
0
to a
7
), when the cosine transformation is performed, include a
0
=x
0
+x
7
, a
1
=x
1
+x
6
, a
2
=x
2
+x
5
, a
3
=x
3
+x
4
, a
4
=x
0
−x
7
, a
5
=x
1
−x
6
, a
6
=x
2
−x
5
and a
7
=x
3
−x
4
, which can be obtained from 8 input image data (x
0
to x
7
). Input data (a
0
to a
7
), when the inverse cosine transformation is performed, includes a
0
=x
0
, a
1
=x
6
, a
2
=x
2
, a
3
=x
4
, a
4
=−x
7
, a
5
=x
1
, a
6
=−x
5
and a
7
=x
3
, which can be obtained from eight input image data (x
0
to x
7
).
The other out of the two 8-8 DCT devices is composed of four selecting circuits adapted to select one piece of input data out of eight pieces of input data (a
0
to a
7
), four fixed coefficient multipliers connected to the selecting circuits and adapted to multiply each of selected signals output from the selecting circuits by a different coefficient and five types of adding/subtracting units connected to outputs of the fixed coefficient multipliers and adapted to perform adding or subtracting operations to each of output signals from the fixed coefficient multipliers in a variety of differently combined ways and is so configured that two types of the adding/subtracting units out of the four types of the adding/subtracting units are used for the cosine transformation and the remaining two types of the adding/subtracting units for the inverse cosine transformation and that eight cosine transformation coefficients are obtained by switching, eight times, the way of selecting data in the selecting circuits, and by switching, eight times, the calculating way from the addition to subtraction or vice versa in the adding and subtracting units and by switching, eight times, the selection of two types of coefficients in the fixed coefficient multipliers. Eight pieces of input data (a
0
to a
7
) for this DCT device are the same as those for the above one out of the two DCT devices.
In both these two DCT devices, DCT coefficients can be calculated by performing the DCT on input data obtained from each line composed of eight pieces of picture element data, which constitutes the block composed of 8×8 pict
Dickstein , Shapiro, Morin & Oshinsky, LLP
Jean-Pierre Peguy
NEC Corporation
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