Image analysis – Image compression or coding – Shape – icon – or feature-based compression
Reexamination Certificate
2001-02-07
2004-11-02
Do, Anh Hong (Department: 2621)
Image analysis
Image compression or coding
Shape, icon, or feature-based compression
C382S232000, C382S240000, C382S236000
Reexamination Certificate
active
06813388
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an image coding method, image coding apparatus and data storage medium and, more particularly, to an image coding method and image coding apparatus which perform coding of an image signal having no shape value in combination with coding of a shape value independent of a pixel value, and generate a multiplex coded signal including shape value information and pixel value information, and a data storage medium which contains a program for implementing the coding process according to the image coding method by software.
BACKGROUND OF THE INVENTION
In recent years, we have greeted the age of multimedia in which audio, video and other data are integrally handled, and the conventional information media (i.e., means for transmitting information to men), such as newspapers, magazines, televisions, radios, and telephones, have been adopted as the subjects of multimedia. Generally, “multimedia” means to represent, not only characters, but also diagrams, speeches, and especially images in relation with each other. In order to handle the conventional information media as the subjects of multimedia, it is necessary to transform the information into a digital format.
When the quantity of data possessed by each information medium described above is estimated as the quantity of digital data, in the case of characters, the data quantity for each character is 1~2 bytes. However, in the case of speech, the data quantity is 64 kbits per second (quality for telecommunication) and, in the case of moving picture, it is more than 100 Mbits per second (quality for current television broadcasting). So, as for most of the information media described above, it is not practical to handle such massive data as it is in the digital format. For example, although visual telephones have already been put to practical use by ISDN (Integrated Services Digital Network) having a transmission rate of 64 kbps~1.5 Mbps, it is impossible to transmit an image of a television camera as it is by the ISDN.
So, data compression technologies are demanded. In the case of visual telephones, the moving picture compression technologies standardized as H.261 and H.263 by ITU-T (International Telecommunication Union-Telecommunication Sector) are employed. Further, according to the data compression technology based on MPEG1, it is possible to record image data, together with audio data, in an ordinary music CD (compact disk).
MPEG (Moving Picture Experts Group) is an international standard of data compression for data of a moving picture (an image signal of a moving picture). In MPEG1, data of a moving picture is compressed to 1.5 Mbps, i.e., data of a television signal is compressed to about 1/100. Since the transmission rate to which MPEG1 is directed is limited to mainly about 1.5 Mbps, MPEG2 is standardized to meet the demand for higher image quality. In MPEG2, data of a moving picture is compressed to 2~15 Mbps.
Under the existing circumstances, standardization of MPEG4 is now proceeded by the working group for standardization of MPEG1 and MPEG2 (ISO/IEC JTC1/SC29/WG11). MPEG4 enables coding and signal processing. in object units, and thereby realizes new functions required in the age of multimedia.
MPEG4 is characterized in that the coding of image signals is performed in object units. In MPEG4, the image signals are not coded in units of frame as an image space having a rectangular shape as in MPEG1 and MPEG2, but the coding of the image signals is performed in object units. To be specific, a shape value which indicates the shape of an object and a pixel value which indicates the design of the object are coded as the image signal.
When the shape value of the object is coded in this way, the new function that the users can freely compose images corresponding to coded image signals and display the images can be realized, as in image composition process in the computer graphics. For the pixel value of a pixel located outside of the object. (outside-object pixel value) which does not require the coding, the coding process can be omitted and thereby the compression rate for the image signal can be improved.
FIG. 24
is a schematic diagram for explaining an image signal including shape information.
The image signal including the shape information includes two signal values, i.e., a pixel value which represents the design of an object to be displayed and a shape value which represents the shape of the object to be displayed. For example, as shown in
FIG. 24
, an image signal including shape information of a moving picture includes pixel values which form each of pixel VOPs (Fv
1
~Fv
5
) and shape values which form each of shape VOPs (Fs
1
~Fs
5
). Here, the pixel VOPs (Fv
1
~Fv
5
) and their corresponding shape VOPs (Fs
1
~Fs
5
) are displayed at display times t
1
~t
5
, respectively, as shown in FIG.
24
.
When a natural image is taken by a camera, an image signal obtained by picture-taking by the camera as the camera output includes only a pixel value out of the two signal values (shape value and pixel value). Thus, in the prior art image coding process, the process for generating a shape value indicating the shape of a specific area (object) in the natural image is performed on the basis of the pixel value included in the image signal, with using the image processing technology for subjecting the frame of the natural image to a processing such as area separation, area segmentation and area extraction.
FIG. 25
is a block diagram illustrating a structure of a prior art image coding apparatus which performs the image coding process, using the shape value according to MEG4.
In MEPG4, the concept equivalent to a frame which constitutes video-of natural images or the like, i.e., the frame which constitutes video of a specific area (object) and which is updated with the passage of time is defined as VOP (video object plane). Further, the coding in MPEG4 is performed in block units and macroblock units as in MPEG1 and MPEG2. Here, the macroblocks are image areas which are obtained by dividing the VOP. Each of the image areas is composed of 16 pixels×16 pixels. The blocks are image areas which constitute the macroblock. Each of the image areas is composed of 8 pixels×pixels.
This image coding apparatus
200
has an IP decision unit
1
for deciding whether a target VOP for which various parameters are set and which is to be coded on the basis of these parameters is assumed to be a VOP subjected to intra-frame coding (I-VOP) or a VOP subjected to inter-frame coding (P-VOP), and outputting a coding mode signal IPmode indicating which type of the coding is to be performed to the target VOP, and a shape extractor
2
for extracting a shape value Spel indicating the shape of the specific area on the basis of the pixel value Vpel associated with the specific area.
This image coding apparatus
200
further has a transparency judgement unit
3
for judging whether the target block in the target VOP to be subjected to the coding requires the coding or not on the basis of the shape value Spel, and outputting the result of the judgement as block transparency information Dtran of the target block, a shape encoder
4
for coding the shape value Sple on the basis of the block transparency information Dtran and the coding mode signal IPmode, and a pixel encoder
5
for coding the pixel value Vpel on the basis of the block transparency information Dtran, the coding mode signal IPmode, and the shape value Spel.
The transparency judgement unit
3
judges whether the pixels in the target block are all outside-shape pixels located outside of the specific area and the target block does not require coding, or at least part of the pixels in the target block are inside-shape pixels located inside of the specific area and the target block requires coding, and outputs the block transparency information Dtran corresponding to the result of the judgement. The shape encoder
4
has a structure which outputs a code for indicating that the target block is an outside-object block when the block transparency
Do Anh Hong
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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