Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1997-10-24
2003-10-14
Kelley, Chris (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
Reexamination Certificate
active
06633611
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for inputting and encoding a moving image and to an apparatus for decoding the encoded moving image. This invention particularly relates to a technique for encoding an image frame by first partitioning it into multiple regions and to a technique for decoding the encoded image frame.
2. Description of the Related Art
FIG. 1
is a block diagram of a first prior art showing the configuration of a moving image encoder based on ITU-T recommendation H.263, wherein numeral
1
indicates an input digital image signal (hereinafter referred to simply as an input image), numeral
101
indicates a differentiator, numeral
102
indicates a prediction signal, numeral
103
indicates a prediction error signal, numeral
104
indicates an encoder, numeral
105
indicates encoded data, numeral
106
indicates a decoder, numeral
107
indicates a decoded prediction error signal, numeral
108
indicates an adder, numeral
109
indicates a local decoded image signal, numeral
110
indicates a memory, numeral
111
indicates a prediction section, and numeral
112
indicates a motion vector.
The input image
1
to be encoded is first input to differentiator
101
. Differentiator
101
takes the difference between input image
1
and prediction signal
102
for output as prediction error signal
103
. Encoder
104
encodes input image
1
, which is an original signal, or prediction error signal
103
, and outputs encoded data
105
. The encoding method in encoder
104
employs a technique in the above-mentioned recommendation where prediction error signal
103
is transformed from a space region to a frequency region using Discrete Cosine Transformation (DCT), a type of orthogonal transformation, and the obtained transformation coefficient is linearly quantized.
Encoded data
105
is branched into two directions, where one is transmitted to a receiver, or an image decoding apparatus (not shown) and the other is input to decoder
106
within the present apparatus. Decoder
106
performs an operation which is the opposite of encoder
104
, and generates and outputs decoded prediction error signal
107
from encoded data
105
. Adder
108
adds prediction signal
102
with decoded prediction error signal
107
and outputs the result as decoded image signal
109
. Prediction section
111
performs motion-compensated prediction using input image
1
and decoded image signal
109
of the previous frame stored in memory
110
, and outputs prediction signal
102
and motion vector
112
. At this time, motion compensation is performed in block units of a fixed size called a macro block comprising 16×16 pixels. As an optional function for a block within a region having large movements, motion-compensated prediction can be performed with the macro block partitioned into four sub-block units of 8×8 pixels. The obtained motion vector
112
is transmitted toward the image decoding apparatus, and prediction signal
102
is sent to differentiator
102
and adder
108
. According to this apparatus, the amount of data of the moving image can be compressed while maintaining image quality through the use of motion-compensated prediction.
In this prior art, the shape of the encoding unit region is limited to two types. Moreover, both shapes are rectangular. Therefore, there is naturally a limit in the encoding which can be adapted to the scene structure or features of an image. For example, if it is desired to increase the amount of code only for an object having large movements, it is preferable, although difficult in this prior art, to define a region having a shape identical to that of the object.
FIG. 2
is a block diagram of an image encoding apparatus concerning a second prior art. This apparatus is based on an encoding method that was proposed in “A Very Low Bit Rate Video Coder Based on Vector Quantization” by L. C. Real et al (IEEE Transactions on Image Processing, Vol. 5, No. 2, February 1996). In the same figure, numeral
113
indicates a region partitioning section, numeral
114
indicates a prediction section, numeral
115
indicates a region determination section, numeral
116
indicates encoding mode information including inter-frame encoding and intra-frame encoding information, numeral
117
indicates a motion vector, numeral
118
indicates an encoder, and numeral
119
indicates encoded data.
In this apparatus, input image
1
is first partitioned into multiple regions by region partitioning section
113
. Region partitioning section
113
determines the size of regions in accordance with the motion-compensated prediction error. Region partitioning section
113
performs judgment using a threshold with regard to dispersion of the inter-frame signal and assigns small blocks to regions having large movement and large blocks to regions, such as backgrounds, having small movement from among ten types of block sizes of 4×4, 4×8, 8×4, 8×8, 8×16, 16×8, 16×16, 16×32, 32×16, and 32×32 prepared in advance. In concrete terms, a dispersion value is calculated by region determination section
115
for the prediction error signal obtained by prediction section
114
, and based on it the block size is determined. Attribute information
116
, such as region shape information and encoding mode information, as well as motion vector
117
are determined at this time, and the prediction error signal or the original signal is encoded by encoder
118
in accordance with the encoding mode information to yield encoded data
119
. Subsequent processes arc the same as those of the first prior art.
This prior art is richer in processing flexibility than the first prior art from the viewpoint of preparing multiple sized blocks. However, this apparatus also limits each region to a rectangular shape. Therefore, even with rectangular shapes in ten sizes, there is room for improvement in adaptability with respect to arbitrarily shaped image regions.
SUMMARY OF THE INVENTION
The present invention takes into consideration these problems with the object of providing a moving image encoding technique for performing more flexible processing according to the conditions of the image to be processed. The object of this invention, in more concrete terms, is to provide a moving image encoding technique using region partitioning techniques that can accurately handle various image structures. Another object of this invention is to provide a partitioning criterion based on various points of view when partitioning regions for encoding. Still another object of this invention is to provide a technique for correctly decoding the encoded data of regions that have been partitioned into various shapes.
The moving image encoding method of this invention includes two steps. A first step partitions an input image into multiple regions based on a predetermined partitioning judgment criterion. Until this point, the encoding process is the same as the general conventional region-based encoding. However, in a second step, this invention integrates each of partitioned multiple regions with adjacent regions based on a predetermined integration judgment criterion. Thereafter, in a third step, the image signal is encoded for each of the regions remaining after integration. According to this method, the integration process allows regions to take on various shapes. Thus, a region having a shape closely matching the structure of an image or outline of an object can be generated.
The moving image encoding apparatus of this invention includes a region partitioning section and an encoder. The region partitioning section includes a partitioning processing section for partitioning the input image into multiple regions based on a predetermined partitioning judgment criterion, and a integration processing section for integrating each of multiple regions partitioned by the partitioning processing section with adjacent regions based on a predetermined integration judgment criterion. The encoder encodes
Asai Kohtaro
Isu Yoshimi
Sekiguchi Shun-ichi
Kelley Chris
Vo Tung
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