Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1997-09-17
2001-02-06
Rao, Andy (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S404100, C348S405100, C348S407100, C348S420100
Reexamination Certificate
active
06185254
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention broadly relates to a data processing method and apparatus, an image encoding method and apparatus, an image decoding method and apparatus, an image transmitting method, and recording mediums. More particularly, the invention relates to a data processing method and apparatus, an image encoding method and apparatus, an image decoding method and apparatus, an image transmitting method, and recording mediums, in all of which quantizing errors are minimized, and temporal jitter of motion pictures, which is caused by a change in the phase of ringing noise between frames, is suppressed.
2. Description of the Related Art
In quantization processing executed to order to perform digital-data compression, input data c is, in general, quantized according to the following equation:
c′=int
(
c/Q
+0.5) (1)
where Q indicates the quantization step size, and into represents the function for rounding down the remainder. In contrast, to perform de-quantization processing for reproducing the data, the following equation is calculated.
c″=c′×Q
(2)
The foregoing two processing operations expressed by the respective equations (1) and (2) are referred to as “linear quantization” and “linear de-quantization”, respectively. The value nQ (n is an integer) of the reproduced data designates, as illustrated in
FIG. 25
, the center value of each of the ranges incremented by the respective quantizing steps, and corresponds to all the input data in a range represented by the following expression.
nQ−Q/
2≦
c<nQ+Q/
2 (3)
On the other hand, nonlinear quantizing processing is executed on the data having a large frequency distribution, such as the one shown in FIG.
26
. More specifically, as shown in
FIG. 27
, a larger level of distribution frequency is quantized by a smaller quantizing step in order to decrease the overall quantizing errors.
FIG. 28
is a schematic diagram illustrating an example of conventional motion-picture encoding apparatuses. In this encoding apparatus
1
, motion-picture data to be encoded is input into a frame memory
12
via an input terminal and stored therein. A motion-vector detector
11
detects a motion vector v from the input image stored in the frame memory
12
generally by performing block matching by a block unit of non-overlapping and small 16×16-pixel regions (hereinafter referred to as “the macroblocks”). Alternatively, to obtain higher precision a matching operation by a half-pixel unit may be sometimes performed.
A motion compensator
20
, which contains a frame memory
21
, predicts the individual pixel values of the image to be encoded from the wholly encoded and partially decoded previous image which is stored in the frame memory
21
. The predicted value I′[i,j,t] of the pixel I[i,j,t] located at the position (i,j) of the image which was input at time t is determined from the motion vector v=(vx(i,j,t), vy(i,j,t)) by the following equation:
I′[i,j,t
]=(
I[i′,j′,t−T]+I[i′+
1,
j′,t−T]+I[i′,j′+
1,
t−T]+I[i′+
1,
j′+
1,
t−T]/
4 (4)
wherein i′ and j′ are expressed by the following equation:
i′=int
(
i+vx
(
i,j,t
)
T
)
j′=int
(
j+vy
(
i,j,t
)
T
)
wherein T indicates a difference between the time at which the image I to be predicted was input and the time at which the previous image stored in the frame memory
12
was input; (I[i′,j′,t−T], I[i′+1,j′,t−T], I[i′,j′+1,t−T], and I[i′+1,j′+1,t−T] on the right side of equation (4) represent the pixel values stored in the frame memory
21
; and int(x) designates the maximum integer not greater than x.
A differential-image generator
13
calculates a difference between the pixel value to be encoded and the predicted value obtained by the motion compensator
20
, and then calculates the sum s of the absolute values of the differences within each macroblock according to the following equation:
[Mathematical equation 1]
S
=
∑
(
i
,
j
)
∈
MB
pq
&LeftBracketingBar;
I
[
i
,
j
,
t
]
-
[
I
′
[
i
,
j
,
t
]
&AutoRightMatch;
&RightBracketingBar;
(
5
)
wherein MB
pq
indicates a macroblock designated by pq. When the value of equation (5) is smaller than the threshold T
1
, each differential value corresponding to the designated macroblock is output. In contrast, when the value of equation (5) is equal to or greater than the threshold T
1
, the pixel value to be encoded rather than the differential value is output. The macroblocks from which the pixel values are output are referred to as “the intra-macroblocks”, while the macroblocks other than the intra-macroblocks are referred to as “the inter-macroblocks”.
The flag f representing whether or not the macroblock to be output is an intra-macroblock is transmitted to a variable-length encoder/multiplexer
16
and is multiplexed with a bit stream, and is further sent to an image adder
19
.
A discrete cosine transform (DCT) unit
14
performs two-dimensional DCT on a 8×8-pixel block. Then, a quantizer(Q)
15
quantizes the DCT coefficient c obtained by the DCT unit
14
by using a suitable step size Q according to the following equation.
c′=int
(
c/Q
) (6)
The quantized DCT coefficient c′ is sent to the variable-length encoder/multiplexer
16
and de-quantizer (Q
−1
)
17
. The de-quantizer
17
de-quantizes the DCT coefficient c′ according to the following equation by using the same step size Q as the one used in the quantizer
15
.
c″=c′×Q
(7)
Inverse DCT (IDCT) is conducted on the de-quantized data which is expressed by a 8×8-pixel block by an inverse discrete cosine transform (IDCT) unit
18
.
The image adder
19
reproduces the pixel value from the data output from the IDCT unit
18
and the predicted value output from the motion compensator
20
in accordance with the flag f transmitted from the differential-image generator
13
. If the flag f represents an intra-macroblock, the data output from the IDCT unit
18
represents the pixel value. Accordingly, no processing is performed in the image adder
19
. In contrast, if the flag f indicates an inter-macroblock, the image adder
19
adds the predicted value from the motion compensator
20
to the data from the IDCT unit
18
, and then reproduces the pixel value. The reproduced pixel value is transmitted to the motion compensator
20
and stored in the frame memory
21
.
The variable-length encoder/multiplexer
16
variable-length encodes and multiplexes the following elements: the DCT coefficient c quantized by the quantizer
15
, the motion vector v detected by the motion-vector detector
11
, and the flag f obtained by the differential-image generator
13
. The multiplexed data in the form of a bit stream is then transmitted to a predetermined transmission line
22
or recorded on a recording medium
23
.
FIG. 29
is a block diagram illustrating an example of a motion-picture decoding apparatus which receives the bit stream output from the motion-picture encoding apparatus
1
shown in FIG.
28
and decodes the received bit stream. The decoding apparatus
31
receives the bit stream from the predetermined transmission line
22
or the recording medium
23
via an input terminal. Then, a de-multiplexer/variable-length decoder
41
variable-length decodes and demultiplexes the bit stream encoded and multiplexed by the variable-length encoder/multiplexer
16
of the encoding apparatus
1
, thereby reproducing the quantized DCT coefficient, the motion vector v, and the flag f from the bit stream. The reproduced DCT coefficient is transmitted to t
Frommer William S.
Frommer Lawrence & Haug LLP.
Rao Andy
Sony Corporation
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