Computer graphics processing and selective visual display system – Computer graphics display memory system – Memory allocation
Reexamination Certificate
2000-11-13
2004-12-28
Tung, Kee M. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics display memory system
Memory allocation
C345S544000, C345S572000, C345S531000
Reexamination Certificate
active
06836273
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a memory management method, an image coding method, an image decoding method, image display method, a memory management apparatus, an image coding apparatus, an image decoding apparatus, an image display apparatus, a memory management program storage medium, an image coding program storage medium, an image decoding program storage medium and an image display program storage medium.
More particularly, the present invention relates to a memory management method which can reduce a memory capacity required for coding, decoding or displaying plural image sequences simultaneously, a method for coding images, decoding images and displaying images utilizing this memory, an apparatus corresponding to these memory management methods and method for coding images, decoding images and displaying images, and a storage medium which contains a program for implementing the respective methods by software.
BACKGROUND OF THE INVENTION
In recent years, we have greeted the age of multimedia in which audio, video and other pixel values are integrally handled, and the conventional information media (i.e., means for transmitting information to people), 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, speech, and especially images simultaneously 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 cases of characters, the data quantity for each character is 12 byte. However, in cases of speech, the data quantity is 64 kbits per second (quality for telecommunication) and, in cases of moving pictures, it is more than 100 Mbits per second (quality for current television broadcasting). So, as for 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 cases 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 a pixel value of a moving picture. In MPEG1, a pixel value of a moving picture is compressed to 1.5 Mbps, i.e., data of a television signal is compressed to about {fraction (1/100)}. Since the transmission rate to which MPEG1 is directed is limited to about 1.5 Mbps, MPEG2 is standardized to meet the demand for higher image quality. In MPEG2, a pixel value 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 processing in units of objects included in an image, and thereby realizes new functions required in the age of multimedia. MPEG4 had originally aimed at standardization of a coding method at a low bit rate, but the aim of standardization has now extended to a more versatile coding process including coding of an interlace image and coding at a high bit rate.
One of the characteristics of MPEG4 is a mechanism for coding and transmitting plural image sequences simultaneously. According to this mechanism, one image scene can be composed of plural images. For example, different image sequences can be used as foreground and background, whereby their frame frequencies, image qualities or bit rates are changed individually. Accordingly, plural image sequences are arranged in the horizontal or vertical direction like a multi-screen on a television receiver or the like, whereby the user can extract or zoom only desired image sequences.
FIG. 15
is a diagram showing a typical example where MPEG coding is performed to an image sequence. This figure shows an example of a frame structure according to MPEG1 or MPEG2. In MPEG4, this corresponds to a reference structure of a VOP of a certain object.
In MPEG coding, there are a frame (I frame) which is coded only by intra-frame operation, a frame (P frame) which is subjected to inter-frame prediction coding performed utilizing the correlation between frames, and a frame (B frame) which is subjected to bidirectional prediction coding performed on the basis of the past frame and the future frame.
FIG. 15
shows the case where MPEG coding is performed to contiguous eight frames FR
1
, FR
2
, . . . , FR
8
. The frames FR
1
and FR
5
are I frames. Other frames, i.e., FR
2
, FR
3
, FR
4
, FR
6
, FR
7
and FR
8
, are P frames.
The I frame can be decoded by itself. However, the P frame cannot be coded or decoded when a frame at the previous time, which is to be referred to, has not been coded or decoded correctly. Therefore, when a transmission error of a bit stream or failure at decoding time occurs, correct image data cannot be obtained until the next I frame is input.
In coding or decoding the P frame, a reference frame is required. Accordingly, the reference frame and one frame for recording data in the process of coding or decoding the present frame, i.e., two frames of the memory, are required for encoding or decoding of one image sequence (object). Similarly, 2n frames of memory area are required for encoding or decoding of n image sequences. Accordingly, in the prior art, the memory address space is divided into 2n pieces, each of the divided areas (banks) is used as one frame of the memory, and the image data is stored therein.
FIG. 16
shows a conventional way of dividing the memory address. In this figure, FM
1
a
, FM
1
b
, FM
2
a
, FM
2
b
, FM
3
a
and FM
3
b
denote a first frame area of a first image sequence, a second frame area of the first image sequence, a first frame area of a second image sequence, a second frame area of the second image sequence, a first frame area of a third image sequence and a second frame sequence of the third image sequence, respectively.
In addition, AD
1
a
, AD
1
b
, AD
2
a
, AD
2
b
, AD
3
a
and AD
3
b
denote a first address start location of the first image sequence, a second address start location of the first image sequence, a first address start location of the second image sequence, a second address start location of the second image sequence, a first address start location of the third image sequence and a second address start location of the third image sequence, respectively. AD
1
a
to AD
1
b
-
1
corresponds to a
1
a
-th memory bank. AD
1
b
to AD
2
a
-
1
corresponds to a
1
b
-th memory bank. AD
2
a
to AD
2
b
-
1
corresponds to a
2
a
-th memory bank. AD
2
b
to AD
3
a
-
1
corresponds to a
2
b
-th memory bank. AS
3
a
to AD
3
b
-
1
corresponds to a
3
a
-th memory bank.
SZ
1
a
, SZ
1
b
, SZ
2
a
, SZ
2
b
, SZ
3
a
and SZ
3
b
denote a first frame size of the first image sequence, a second frame size of the first image sequence, a first frame size of the second image sequence, a second frame size of the second image sequence, a first frame size of the third image sequence, and a second frame size of the third image sequence, respectively.
Here, the way of storing image data of each image sequence is described taking the case of decoding the frames FR
1
, FR
2
, . . . , FR
8
in
FIG. 15
as an example.
Assume that these frames FR
1
, FR
2
, . . . , FR
8
constitute one image sequence (assuming the first image sequence). This
Matsushita Electric - Industrial Co., Ltd.
Tung Kee M.
Wenderoth , Lind & Ponack, L.L.P.
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