Image analysis – Image compression or coding – Adaptive coding
Reexamination Certificate
1999-09-29
2001-10-30
Couso, Jose L. (Department: 2621)
Image analysis
Image compression or coding
Adaptive coding
Reexamination Certificate
active
06310981
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a coding and decoding apparatus for coding information such as an image signal etc. to transmit it and decoding the coded data. More detailedly, the present invention relates to a coding and decoding apparatus which enables communication between coding and decoding tools having different processing capacities and in which the coding apparatus transmits not only the coded data but also coding information for the construction of a decoding scheme as the means of decoding the coded data and the decoding apparatus receives the coding information together with coded data and reconstructs the decoding scheme based on the coding information so as to decode the received coded data. Further, the present invention is directed to a coding and decoding technology for performing the communication in a coding and decoding apparatus between the transmitting and receiving devices having different capacities in the case where an algorithm includes various coding and decoding tools such as near-future image coding schemes represented by the MPEG4 etc., and more particularly relates to a coding and decoding apparatus which enables simultaneous transmission of coded data and tool information for constructing the algorithm for decoding the coded data in order to realize a hierarchical coding and decoding operation.
(2) Description of the Background
In recent years, a wide spread of ISDN (Integrated Services Digital Network) has realized image communication services as a new communication service. Examples of the services include the video phone and video conference system, etc. On the other hand, the development of the mobile communication networks represented by the PHS and the FPLMTS, accelerates demands for further improvement and variations of the services and portability of the devices.
In general, in the case where image information as in the video phone or video conference system is transmitted, the amount of image information is very large. However, due to the line speed used for the transmission and the cost problem, the image information to be transmitted needs to be compressed and coded so that the amount of information can be reduced.
As to the coding schemes for compressing image information, JPEG(Joint Photographic coding Experts Group) has already been standardized internationally for a still image coding system, H.261 for a motion picture coding scheme, and MPEG1(Moving Picture Coding Experts Group) and MPEG2 for motion picture coding schemes. Further, MPEG4 is now being standardized as a coding scheme of very low-bit rate of 64 kbps or below.
In the current coding schemes such as JPEG, H.261, MPEG1, MPEG2, coding is performed following the specified algorithm. However, the MPEG4 is planned to flexibly deal with various applications and encode each of the applications in its optimal scheme. For this purpose the MPEG4 needs to have many tools (such as transformer, quantizer, inverse transformer, inverse quantizer, etc.) for its coder so that a suitable combination of them will be selected to perform coding.
FIG. 1A
is a conceptual view showing the structure of a coding data stream which is formed by coding (compressing) image data based on the H.261 scheme. Each piece of the coded data such as motion vector information, DCT-coefficient, quantization step, etc., shown in
FIG. 1A
is image data which has been coded (compressed) based on a fixed coding algorithm in the coder, while the decoder has a decoding algorithm fixed corresponding to the coding algorithm so that the received pieces of the coded data will be decoded.
FIG. 1B
is a conceptual view showing the structure of a coding data stream which is formed by coding (compressing) image data based on a coding scheme such as MPEG4 etc. whose algorithm is flexible. The coding data stream as shown in
FIG. 1B
is composed of coded (compressed) image data such as motion vector information
2
, transform coefficient
4
, motion vector information
6
, transform coefficient
8
and quantization step
10
etc., and tool information such as motion compensation tool
1
, inverse transform tool
3
, motion compensation tool
5
, inverse transform tool
7
and quantizing tool
9
, etc., for decoding respective image data.
FIG. 1B
illustrates the details of the motion vector information, DCT-coefficient and quantization step at the leading end of the coding data stream of FIG.
1
A. In this case, each piece of the tool information such as motion compensation
1
etc., is allowed to be selected from a number of types of the tool information so that it is possible to freely select a desired combination of the tool information. Accordingly, the coder transmits the tool information which has been used for coding as well as the image data to the decoder. The decoder, upon the decoding of the image data received, will decode the coded image data using the tool information transmitted from the coder.
FIG. 1C
is a block diagram showing an example of a conventional coding and decoding apparatus based on H.261. This coding and decoding apparatus is composed of a controller
6
a
for controlling the entire apparatus, a coder
7
a
for coding based on H.261, and a decoder
8
a
for decoding the information which has been coded based on H.261, and a tool storage section
9
a
consisting of memories for storing tool information.
These coding and decoding processes can be realized by a dedicated hardware device with software installed therein or by an appropriate program executed in a general-purpose processor with a compiler.
First, description will be made of a method using a dedicated hardware device with software installed therein.
FIG. 2
is a block diagram showing the configuration of coder
7
a
of
FIG. 1C
for yielding the coded data shown in
FIG. 1A
, based on H.261. In
FIG. 2
, the coder is composed of: a coding controller
11
for the control of coding; a transformer
12
for performing the DCT; a quantizer
13
for quantizing the coefficients transformed by transformer
12
; an inverse quantizer
14
for performing inverse quantization of the coefficients quantized in quantizer
13
; an inverse transformer
15
for performing the inverse DCT; a memory
16
; and a loop filter
17
. Here, memory
16
has the function of causing a variable delay for motion compensation, used when the inter-frame prediction for motion compensation is performed. Filter
17
is the loop filter capable of performing the on/off operation for each of macro blocks.
When the coding algorithm for generating the coding data stream shown in
FIG. 1A
is executed by the dedicated hardware device with software, the tool functions constituting the algorithm are carried out by software and the dedicated hardware components as shown in
FIG. 2
, namely, coding controller
11
, transformer
12
, quantizer
13
, inverse quantizer
14
, inverse transformer
15
, memory
16
having the function of causing a variable delay for motion compensation, and loop filter
17
.
FIG. 3
is a block diagram showing the configuration of decoder
8
a
shown in
FIG. 1C
for decoding the coded data based on H.261. This decoder commonly has the constituents of the coder shown in
FIG. 2
, and the same components as those in the coder of
FIG. 2
are designated at the same reference numerals. Specifically, in
FIG. 3
, a reference numerals
14
designates an inverse quantizer,
15
an inverse transformer,
16
a memory having the function of causing a variable delay for motion compensation, and
17
a loop filter.
The coded data by the coder shown in
FIG. 2
is inverse quantized by inverse quantizer
14
, and the signal is then made to undergo the inverse DCT in inverse transformer
15
. Here, memory
16
and loop filter
17
are used when the motion compensated prediction coding data is decoded.
When several kinds of algorithms need to be processed using the scheme which performs the coding operation based on a fixed algorithm such as H.261 etc. as stated above, an individual hardware device with softw
Koizumi Noritaka
Makiyama Takeshi
Sato Seiji
Uchiumi Tadashi
Couso Jose L.
Sharp Kabushiki Kaisha
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