Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1999-01-19
2002-06-11
Le, Vu (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06404815
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of prior PCT International Application No. PCT/JP97/03825 which has an International filing date of Oct. 23, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
1. Technical Field
The present invention relates to a highly efficient picture (image) encoding and decoding system for performing motion compensated prediction of a picture (image) to be encoded or decoded for encoding a prediction error, and for decoding reference picture (image) data together with the prediction error by referring to an encoded picture (image).
2. Background of the Invention
Conventional motion compensated prediction methods for performing highly efficient encodation of a picture are described below.
The first example of a conventional motion compensated prediction method which will be discussed is a motion compensated prediction method using block matching that compensates for translational motion of an object. For example, in ISO/IEC 11172-2 (also known as the MPEG 1 video standard), a forward/backward/interpolative motion compensated prediction method using block matching is described. The second example of a conventional motion compensated prediction method which will be discussed is a motion compensated prediction method using an affine motion model. For example, “Motion Compensated Prediction Using An Affine Motion Model” (the technical report of IE94-36, by the Institute of Electronics, Information and Communication Engineers of Japan) describes the motion compensated prediction method in which the displacement of an object in each arbitrarily shaped segment is modeled and expressed using affine motion parameters, and in which the affine motion parameters are detected so as to perform motion compensated prediction.
Now, the conventional motion compensation method using block matching by a translational motion and the conventional motion compensation method using the affine motion model will be described in more detail below.
FIG. 42
shows a known motion compensated prediction which utilizes block matching. In
FIG. 42
, i represents a position of a block on a display as a unit used for motion compensated prediction; fi(x, y, t) represents the pel value (x, y) in the block i at time t on the display; R represents a motion vector search range; and v represents a motion vector (&egr;R). Block matching is a process for detecting, within the search range R of a reference picture
201
, a block whose pel value is most approximate to the pel value fi(x, y, t) of the block i in an input picture
202
, or for detecting a pel value fi+v (x, y, t−1) which will minimize a prediction error power Dv which may be expressed in one of the following equations (1)
D
v
=
∑
x
,
y
{
f
i
+
v
(
x
,
y
,
t
-
1
)
-
f
i
(
x
,
y
,
t
)
}
2
or
∑
x
,
y
|
f
i
+
v
(
x
,
y
,
t
-
1
)
-
f
i
(
x
,
y
,
t
)
|
(
1
)
The value v which minimizes Dv will be the motion vector. In
FIG. 42
, a block matching search method using real sample point integer pels in a reference picture is referred to as an integer pel precision search, and a block matching search method using half-pels (interposed midway between the integer pels) in addition to integer pels is referred to as a half-pel precision search. Generally, under the same block matching search range, more search pel points can be obtained in the half-pel precision search than in the integer pel precision search. Consequently, increased prediction accuracy will be obtained with the half-pel precision search.
FIG. 43
is a block diagram showing a configuration of a motion compensated predictor (also referred to as a block matching section) using a motion compensated prediction method in accordance with, for example, the MPEGI video standard.
In the figure, reference numeral
207
is a horizontal displacement counter,
208
is a vertical displacement counter,
211
is a memory readout-address generator,
213
is a pattern matching unit, and reference numeral
216
is a minimum prediction error power determinator. Reference numeral
203
is a horizontal displacement search range indication signal,
204
is a vertical displacement search range indication signal,
205
is input picture block data,
206
is an input picture block position indication signal,
209
is horizontal displacement search point data,
210
is vertical displacement search point data,
212
is a readout address,
214
is readout picture data,
215
is a prediction error power signal,
217
is a motion vector,
218
is a minimum prediction error power signal, and
219
is a frame memory for storing reference picture data.
FIG. 44
is a flow chart showing the operations of the conventional motion compensated predictor having the above-mentioned configuration of FIG.
43
.
In
FIG. 44
, dx represents a horizontal displacement search pel point;
dy represents a vertical displacement search pel point;
range_h_min represents a lower limit in a horizontal displacement search range;
range_h_max represents an upper limit in the horizontal displacement search range;
range_v_min represents a lower limit in a vertical displacement search range;
range_v_max represents an upper limit in the vertical displacement search range;
D_min represents the minimum prediction error power;
(x, y) are coordinates representing the position of a pel in a macroblock;
D(dx, dy) represents prediction error power produced when dx and dy are searched;
f(x, y) is the value of a pel (x, y) in an input picture macroblock;
fr(x, y) is the value of a pel (x, y) in a reference picture;
D(x, y) is a prediction error for the pel (x, y) when dx and dy are searched;
MV_h is a horizontal component of a motion vector (indicating horizontal displacement); and
MV_v is a vertical component of a motion vector (indicating vertical displacement).
The block matching operation will be described in more detail, by referring to
FIGS. 43 and 44
.
1) Motion Vector Search Range Setting
Range_h_min and range_h_max are set through the horizontal displacement counter
207
according to the horizontal displacement search range indication signal
203
. Range_v_min and range_v_max are set through the vertical displacement counter
208
according to the vertical displacement search range indication signal
204
. In addition, the initial values of dx for the horizontal displacement counter
207
and dy for the vertical displacement counter
208
are set to range_h_min and range_v_min, respectively. In the minimum prediction error power determinator
216
, the minimum prediction error power D_min is set to a maximum integer value MAXINT (for example, OxFFFFFFFF). These operations correspond to step S
201
in FIG.
44
.
2) Possible Prediction Picture Readout Operation
Data on the pel (x+dx, y+dy) in a reference picture, which are distant from the pel (x, y) in the input picture macroblock by dx and dy are fetched from the frame memory. The memory readout address generator
211
illustrated in
FIG. 43
receives the value of dx from the horizontal displacement counter
207
and the value of dy from the vertical displacement counter
208
, and generates the address for the pel (x+dx, y+dy) in the frame memory.
3) Prediction Error Power Calculation
First, the prediction error power D(dx, dy) for the motion vector representing (dx, dy) is initialized to zero. This corresponds to step S
202
in FIG.
44
. The absolute value for the difference between the pel value readout in 2) and the value of the pel (x, y) in the input picture macroblock is accumulated into D(dx, dy). This operation is repeated until the value of x and the value of y become x=y=16. Then, the prediction error power D(dx, dy) produced when (dx, dy) is searched, or Dv given by numeral equations (1) is obtained. This operation is executed by the pattern matching unit
213
illustrated in FIG.
43
. Then, the pattern matching unit
213
supplies D(dx, dy) to the minimum p
Asai Kohtaro
Hasegawa Yuri
Isu Yoshimi
Kuroda Shin-ichi
Murakami Tokumichi
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