Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1999-06-04
2001-08-07
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C345S182000, C345S156000, C345S156000
Reexamination Certificate
active
06271827
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display system in an information processing apparatus such as a portable information terminal and a personal computer.
2. Description of the Related Art
In general, display data is displayed by a display apparatus such as a cathode ray tube (CRT) or a liquid crystal display (LCD) in a display system of an information processing apparatus such as a portable information terminal and a personal computer.
FIG. 4
shows a configuration of a conventional display system
400
. The display system
400
includes a display apparatus
41
, a display memory
42
, and a memory control circuit
43
. The memory control circuit
43
is connected to a CPU
44
via a system data bus
45
, and is controlled by the CPU
44
.
In the display system
400
, display data is transferred from the CPU
44
to the display memory
42
non-periodically and is stored in the display memory
42
, while display data is transferred from the display memory
42
to the display apparatus
41
periodically and successively.
When the display system
400
performs color display, a color image signal is transmitted between the display apparatus
41
and the memory control circuit
43
. The color image signal has either one of two formats. One is an RGB format and the other is a YUV format. Herein, the color image signal of the RGB format (i.e., RGB data) consists of three kinds of signals representing three primary colors (red, green, and blue). The color image signal of the YUV format (i.e., YUV data) consists of a luminance signal Y and a color-difference signal UV. In general, the YUV data is finally converted into the RGB data in the display apparatus, and color display is realized using the RGB data. The RGB data has better consistency with data which is to be finally processed in the display apparatus, while the YUV data represents better compression characteristics than the RGB data. Each of the two formats is used appropriately in view of these features of the formats.
Hereinafter, examples of various RGB formats and YUV formats will be described with reference to
FIGS. 5A
to
5
D.
FIG. 5A
shows an RGB 8:8:8 format as one example of the RGB format. According to the RBG 8:8:8 format, 8 bits are assigned to each color of RGB, and each color is represented in 256-level gray scales, whereby about 16,000,000 colors are produced by 24 bits in total.
FIG. 5B
shows an RGB 5:6:5 format as another example of the RGB format. According to the RGB 5:6:5 format, color data per dot is represented by 16 bits, in view of the consistency with data processed by the CPU. Each color of RGB is represented by 5 bits, 6 bits, and 5 bits, respectively.
FIG. 5C
shows a YUV 4:4:4 format as one example of the YUV format. 8 bits are assigned to each of Y, U, and V. Color data per dot is represented by 24 bits in total.
FIG. 5D
shows a YUV 4:2:2 format as another example of the YUV format. Color data per dot is represented by 16 bits, in view of the consistency with data processed by the CPU. According to the YUV 4:2:2 format, the YUV data includes YU data and YV data. The YU data and the YV data are alternately repeated per dot. The YU data has a Y signal of 8 bits and a U signal of 8 bits. The YV data has a Y signal of 8 bits and a V signal of 8 bits.
When display data of the RGB format is transferred between the display apparatus
41
and the memory control circuit
43
, display data is also stored in the display memory
42
in the RGB format. Furthermore, display data is also written and read by the CPU
44
in the RGB format.
Similarly, when display data of the YUV format is transferred between the display apparatus
41
and the memory control circuit
43
, display data is also stored in the display memory
42
in the YUV format. Furthermore, display data is also written and read by the CPU
44
in the YUV format.
Thus, in the case where the format of the display data which is transferred from the CPU
44
to the display memory
42
is determined as a fixed format (i.e., either one of the RGB format or the YUV format), the format of data used in the display system
400
should be the same as the fixed format. However, in the case where the format of the display data which is transferred from the CPU
44
to the display memory
42
may sometimes match with the RGB format and may sometimes match with the YUV format, special data processing is required for writing display data in a format which is not matched with the data format in the display system.
For example, it is assumed that a display system includes a display memory for storing display data of the RGB format and a display apparatus for displaying the display data of the RGB format. In this case, if display data of the YUV format is transferred from the CPU to the display system, the display system cannot display the display data of the YUV data appropriately. The display data of the YUV format is first required to be converted into the display data of the RGB format. Such a conversion is made, for example, by software processing. The converted display data of the RGB format is stored in the display memory. In this case, the display system has the same hardware configuration as that of a display system which simply uses the RGB format.
FIG. 6
shows a configuration of another conventional display system
600
. The display system
600
includes a data converter
61
dedicated for converting display data of the YUV format into display data of the RGB format and vice versa in addition to the elements in the display system
400
shown in FIG.
4
. In the display system
600
, display data of the YUV format is once written in the data converter
61
, and the display data of the YUV format is converted into the display data of the RGB format. Then, the display data of the RGB format, which has been converted and output by the data converter
61
, is read, and the read display data is written in the display memory
42
.
Still another conventional display system is disclosed in Japanese Laid-Open Publication No. 61-144190. In such a display system, display data (image data) is supplied through a transmission path such as a telephone line, not from a CPU, and the supplied display data is converted from a YUV format into an RGB format and given to a display memory (frame memory). In this display system, an ID signal for identifying a format of display data is added to the display data. Display data is identified to be either in the RGB format or in the YUV format by detecting the ID signal. In the case where display data is identified in a YUV format, the display data is converted from a YUV format into an RGB format and stored in a display memory.
For the above-mentioned conversion of display data from a YUV format into an RGB format, the following conversion equations represented by equation (1-1) to equation (1-3) are generally used.
R
=Y+
1.402
V
(1-1)
G
=Y−
0.714
V−
0.344
U
(1-2)
B
=Y+
1.772
U
(1-3)
Depending upon the YUV-formatting procedure in a stage where display data of interest is created, a coefficient applied to the above-mentioned equations (1-1) to (1-3) may be varied. However, it is basically required to multiply an original signal value of YUV by a certain coefficient and obtain a sum (or difference) thereof.
The conventional display system
400
(
FIG. 4
) has the following problem. In the case where a display system using display data in both a YUV format and an RGB format has a hardware configuration for only the RGB format, while conversion from the YUV format into the RGB format is performed by software processing, the software processing for the sum of products operation in conversion from the YUV format into the RGB format involves a large number of programming steps. Therefore, it takes much time to perform such sum of products operation processing. This causes much more time to be spent for converting display data from a YUV format into an RGB format and writing the display data in a display
Havan Thu-Thao
Luu Matthew
Sharp Kabushiki Kaisha
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