JPH08129368A - Graphics subsystem and control method therefor - Google Patents

Abstract

PURPOSE: To perform full color display by using a circuit of a small scale and the capacity of a frame memory. CONSTITUTION: This graphics subsystem is provided with a frame memory housing digital image data of RGB form and YUV form together with attribute data, a buffer/multiplexer 40 reading out the data from the frame memory, a color palette 41 transforming a palette number and color data for the data of RGB form, a multiplexer 42 selecting the data of RGB form through the color palette 41 or the data of YUV form in the buffer/multiplexer 40 based on the attribute data, AND gates 43, 44, a YUV type DA converter part 45 and an RGB type DA converter part 46 converting digital image data of YUV form and RGB form into analog data, respectively, a DA converter 22 including a mixer 47 synthesizing both outputs and a graphics accelerator controlling the frame memory and the DA converter 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphics subsystem in an information processing system, and in particular, a so-called bitmap display such as a small computer, a workstation (hereinafter abbreviated as WS) and a personal computer (hereinafter abbreviated as PC) is connected. The present invention relates to a technique suitable for realizing a low-priced and small-sized graphics subsystem in a possible information processing system.

[0002]

2. Description of the Related Art Needless to say, in information processing systems, particularly small computers, WSs, and PCs, the graphics subsystem has a large weight in each system. Here, a conventional technology is shown taking a graphics subsystem for a PC as an example.

For example, Nikkei BP, June 2, 1994.
As described in the literature such as the 1st issue, Nikkei Bytes Separate Volume No. 2, "Latest Personal Computer Technology", P73-P90, etc., the graphics subsystem for PC is currently popular in the graphical user interface (GUI). Along with,
In the past, the direction of providing a comfortable user interface by speeding up the processing by adopting a dedicated LSI called a graphics accelerator that executes a part of the two-dimensional drawing function that was previously processed by the CPU in the graphics subsystem. Has been developed in.

Further, due to the increasing needs for so-called video (moving image) processing, a graphics accelerator LSI
There is a type in which a video processing function is built in or a dedicated LSI called a video accelerator and a subsystem are added as another LSI to speed up the processing.

These video accelerators decompress compressed video data given from the outside and digitally convert the data into a format that can be stored in a frame memory (generally used as a color storage format of video data. Most of the processing is performed after the YUV format is converted into a general RGB format in a graphics subsystem in an information processing apparatus, so-called color space conversion, and then the data is stored in a frame memory (for example,
Published by Nikkan Kogyo Shimbun on August 10, 1991, "Digital Video Recording Technology" P1 to P15).

[0006]

The color space conversion of the video accelerator must be performed by the following matrix conversion if it is to be realized by a digital circuit.

[0007]

[Equation 1]

The above formula is not so complicated, but it requires a considerable number of gates to be realized by a digital circuit, and the circuit scale becomes large, so that it is attempted to be realized by the same LSI as the graphics accelerator. It is an obstacle to the above.

In particular, when video data occupies a large area, that is, when displaying a large amount of video data, the amount of data to be processed increases and it becomes difficult to process in real time.

Further, in the YUV format, so-called full color is expressed by 4 bits for each YUV by utilizing the low resolution with respect to the color of human eyes, whereas in the RGB format, each color for each RGB must be about 8 bits. It is not a full color expression.

Therefore, after conversion from the YUV format to the RGB format, the amount of data increases, and the capacity of the frame memory for storing the video data is required to be doubled.

An object of the present invention is to realize full-color display without requiring a digital circuit for color space conversion for video data processing, which has a large circuit scale.

Another object of the present invention is to realize full color display without a large capacity frame memory.

[0014]

According to the present invention, the data stored in the frame memory can be stored in either the RGB format or the YUV format, and the attribute indicating which format the stored data is. It also stores data.

In addition, the data stored in the YUV format is read as R
The GB conversion uses an analog circuit instead of a digital circuit to suppress an increase in circuit scale and improve real-time processing performance. When it is realized by an analog circuit, it can be realized by a simple addition circuit.

[0016]

According to the present invention, normal drawing data used in GUI or the like is stored in the frame memory in RGB format,
Data in RGB format is converted to digital / analog converter (DA
It can be converted into analog data by a converter and displayed on a display device.

Data input in YUV format from outside the graphics subsystem, such as video data, is stored in the frame memory in its original format without color space conversion. At this time, the attribute data indicating that the data stored in the frame memory is in the YUV format is simultaneously written in the frame memory.

Correctly displaying the YUV format data means that the attribute data is also read at the same time when the display data is read from the frame memory, and if the attribute data is in the YUV format, the circuit is used in the digital / analog conversion section. Correct YU by changing the constant for YUV
It is possible to convert V format data into RGB format analog data.

Therefore, it is not necessary to convert the YUV format data into the RGB format and store it in the frame memory, which has conventionally required a very large processing capacity.
RGB format data in the same frame memory is also YUV
Format data can also be displayed correctly. This makes it possible to control high-quality video data at a low price.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of an information processing system using a graphics subsystem and its control method according to an embodiment of the present invention. In FIG. 1, reference numeral 10 is a bus for connecting each component in the system, which is composed of a plurality of signal lines. 1
Reference numeral 1 is an information processing device (CPU) that controls the entire information processing system, 12 is a memory, 13 is a bus controller that performs competition control on the bus, and 14 is an input / output that performs input / output processing such as a file subsystem or a network subsystem. It is a device (I / O).

Reference numeral 15 in FIG. 1 is a graphics subsystem according to this embodiment. Since the graphics subsystem 15 enables display with a maximum resolution of 1280 × 1024, it has a V capacity of 2 MB as a frame memory.
A RAM is mounted, and display data is sent to the display device 16 through an RGB analog display signal line 17 formed of three sets of signal lines to display the data.

FIG. 2 is a block diagram showing an example of the configuration of the graphics subsystem of this embodiment. The graphics accelerator 20 draws the display data input via the bus 10 via a frame memory access signal line 23 into a frame memory 21 composed of eight 2 Mbit VRAMs (× 8 bit configuration), and Similarly, it decodes and executes various drawing commands input via the bus 10 and draws them in the frame memory 21. The DA converter 22 performs digital / analog conversion on the data in the frame memory 21 input via the frame memory display read signal line 25 including 64 data signal lines, and R
Display data is transmitted through the GB analog display signal line 17.

FIG. 3 is a block diagram showing an example of the arrangement of the graphics accelerator in the graphics subsystem according to this embodiment. The graphics accelerator 20 is directly connected to the bus 10. An access from the bus is received by the bus interface control unit 30, and the DA converter control unit 31, the video data enlargement / reduction control unit 32, or the drawing instruction execution unit 33 receives the access address. The predetermined data is transmitted and received. D
The A converter control unit 31 controls access to the DA converter 22 that is not directly connected to the bus 10. The A converter control unit 31 controls the bus 10 and the DA converter access control line 2.
Interface conversion between 4 is performed. The video data enlargement / reduction control unit 32 multiplies the YUV format video data of a specific size input from the bus 10 to a specific size on the frame memory 21 by m / n times (m, n: natural numbers) in each direction. is there. When m> n, that is, when enlargement is performed, color interpolation is performed between data of adjacent pixels.
This interpolation is performed in the YUV format. Further, when the number of bits representing the color per pixel is insufficient in color interpolation by simple linear interpolation, interpolation by dither is also used.

This is the only part of the graphics accelerator 20 that performs special processing on the video data. Therefore, the graphics accelerator 20 does not convert the YUV format video data into the RGB format. The drawing command execution unit 33 executes drawing commands such as line drawing, closed figure filling, copying, and image data development used for GUI and the like, and performs processing of drawing data in the frame memory 21 in RGB format. The drawing data and drawing coordinates generated by the video data scaling control unit 32 and the drawing command execution unit 33, and the attribute data created by the attribute data generation unit 35 are converted into a frame memory access interface in the frame memory control unit 34. And written.

FIG. 4 is a block diagram showing an example of a DA converter which constitutes the graphics subsystem of this embodiment. The data sent from the frame memory display read signal line 25 including 64 data signal lines is D
After being latched by the buffer / multiplexer 40 in the A converter 22, it is classified into display data and attribute data. When using pseudo color, the palette number and color data are converted by the color palette 41 as needed. If it is not pseudo-color or if the attribute data indicates that it is YUV format display data, the display data does not go through the color palette 41 and the multiplexer 4 is used.
Entered in 2. The multiplexer 42 selects the data from the color palette when the display data is RGB format data and pseudo color according to the attribute data,
Otherwise, the data from buffer / multiplexer 40 is selected. The data from the multiplexer 42 is sent to the YUV format DA converter 45 via the AND gate 43 in the case of YUV format and to the RGB format DA converter 46 via the AND gate 44 in the case of RGB format according to the attribute data. . Each DA converter outputs RGB analog data in accordance with the input data.

The RGB format analog data output from the YUV format DA conversion section 45 and the RGB format DA conversion section 46 is sent to the outside of the DA converter 22 via a mixer 47 which is an analog circuit.

FIG. 5 is a conceptual diagram showing an example of a data storage format in the frame memory 21 which constitutes the graphics subsystem of this embodiment. In this embodiment, 1280
An 8-plane frame buffer having a display area of × 1024 is composed of eight 2 Mbit VRAMs. The maximum simultaneous displayable color is 256 colors in the RGB format.
The address is shown for each byte, but since drawing writing and display reading are actually performed in units of 64 bits, for example, addresses 0x0000 to 0x00.
07 are simultaneously accessed.

The pixel numbers shown in the legend in FIG. 5 correspond to the respective pixels on the display device 16 in a one-to-one correspondence, and 0 at the upper left corner on the display screen.
Numbers are assigned in ascending order from the number to the right, one by one. The top right pixel on the display screen is number 1279, which is 0
The number of pixels immediately below the number is 1280.

The bit of [pixel number, b] shown in the legend in FIG. 5 indicates whether the pixel is in RGB format or YUV format. When the bit value is 0, it is RGB format, and when it is 1, it is Y.
Indicates that it is in UV format.

The display data drawn in the RGB format is stored only in the area shown in parentheses. For example, if the pixel number 0 is in RGB format, an arbitrary value from 0x00 to 0xFF is written in the address 0x0000, and in the case of pseudo color, this value becomes the palette number.

At this time, [0, b] of the address 0x0008 is set to 0, indicating that it is in RGB format. Y
The display data drawn in the UV format is stored in the area indicated by the round brackets and the area indicated by the square brackets. For example pixel 1
If the number is YUV format, the address is 0x0001
Is any value from 0x00 to 0xFF, and the address 0x
0x0 to 0 from [1,8] to [1, a] of 0008
Any value of x7 is written, and [1, b] is 1
Indicates that the format is YUV. Like this YUV
In the format, 11 bits per pixel can be used, and the luminance and the two color difference information forming the YUV data can be stored as 4 bits, 4 bits, and 3 bits, respectively, and high-quality full-color video image data can be stored. The display read from the frame memory 21 is performed by the frame memory display read signal line 25 having 64 data signal lines. / Data can be matched by buffering with the multiplexer 40. When the number of display clocks is 135 MHz, the display reading of the frame memory 21 is about 25 MHz, which can be realized without using a special circuit.

Further, in the present embodiment, the data other than the RGB format is the YUV format, but it is also possible to use the RGB format using 11 bits which can be freely used. In this case, usually 256 colors of 8 bits of RGB and 2048 colors of 11 bits of RGB can be mixed.

As described above, according to the graphics subsystem and its control method of this embodiment, R
When not only the GB format but also the YUV format data is still digital, it is provided for each of the RGB format and the YUV format based on the attribute data when it is written to the frame memory 21 together with the attribute data and output to the display device 16. RGB format DA converter 46 and YUV format DA
Since the conversion unit 45 individually converts the analog data, the YUV format digital data is converted to RGB format digital data as in the prior art, and then the frame memory 21 is converted.
Since a digital circuit for writing in is unnecessary, full-color display of image data in a mixture of RGB format and YUV format is possible with a smaller circuit scale.

Further, since the conversion from the YUV format to the RGB format is not performed in the digital state, it is not necessary to increase the capacity of the frame memory 21 in order to hold the data which is increased during the conversion. DA
The reading speed of the data to the converter 22 is set sufficiently higher than the output speed of the analog data in the RGB format from the DA converter 22 to the display device 16, so that the frame memory 21 having a smaller capacity can be used in the RGB format and the YUV format. Full-color display of mixed image data is possible.

As a result, the control of the image data in which the video data is mixed can be performed at low cost and with high quality.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the image data stored in the frame memory is not limited to the combination of the RGB format and the YUV format, but three or more kinds of digital image data having different expression formats are stored in the frame memory as they are and read from the frame memory. The digital image data of each format
The present invention includes a configuration in which an analog conversion circuit is provided to convert into analog image data.

[0039]

According to the graphics subsystem of the present invention, full-color display can be realized without the need for a digital circuit for color space conversion for video data processing, which has a large circuit scale. Is obtained. Further, there is an effect that full color display can be realized without a large capacity frame memory.

According to the control method of the graphics subsystem of the present invention, the digital circuit for color space conversion for video data processing, which has a large circuit scale, is not required,
The effect that full-color display can be realized is obtained. Further, there is an effect that full color display can be realized without a large capacity frame memory.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an information processing system using a graphics subsystem and a control method therefor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a configuration of a graphics subsystem that is an embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a graphics accelerator configuring a graphics subsystem that is an embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a DA converter that constitutes a graphics subsystem that is an embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an example of a data storage format in a frame memory which constitutes a graphics subsystem that is an embodiment of the present invention.

[Explanation of symbols]

10 ... Bus, 11 ... Information processing device (CPU: host device), 12 ... Memory, 13 ... Bus controller, 14 ...
Input / output device (I / O), 15 ... Graphics subsystem, 16 ... Display device, 17 ... RGB analog display signal line, 20 ... Graphics accelerator, 21 ... Frame memory, 22 ... DA converter, 23 ... Frame memory access Signal line, 24 ... DA converter access control line, 25 ... Frame memory display read signal line, 30
... bus interface control unit, 31 ... DA converter control unit, 32 ... video data scaling control unit, 33 ... drawing command execution unit, 34 ... frame memory control unit, 35 ... attribute data generation unit, 40 ... buffer / multiplexer, 41
... color palette, 42 ... multiplexer (input switching means), 43 ... AND gate (input switching means),
44 ... AND gate (input switching means), 45 ... YU
V format DA converter (digital / analog converter), 4
6 ... RGB format DA converter (digital / analog converter), 47 ... mixer (combining means).

Claims (3)

[Claims] 1. A graphics subsystem for converting at least digital image data coming from a higher-level device into analog image data and outputting the analog image data to a display device, the plurality of types having different expression formats coming from the higher-level device. Of the digital image data and a frame memory storing attribute data for identifying a plurality of types of the digital image data, and a plurality of types of the digital image data read from the frame memory are individually converted into the analog image data. A plurality of digital / analog converters, input switching means for switching input of each of the digital image data to each of the plurality of digital / analog converters based on the attribute data read from the frame memory, The digital analog And a synthesizing unit for synthesizing the analog image data output from the image conversion unit and outputting the synthesized analog image data to the display device. 2. A method of controlling a graphics subsystem for processing and displaying graphics data in an information processing system, the reading speed of the graphics data from a frame memory comprising a plurality of planes for storing the graphics data. Is set to be higher than the speed of sending from the graphics subsystem to the display device, thereby making it possible to display a larger number of colors than the number of planes present in the frame memory that can be simultaneously displayed. A method for controlling a graphics subsystem characterized by the above. 3. The graphics data stored in the frame memory in the graphics subsystem is display data in RGB format and YUV format which are different in expression format and are sent to the display device.
3. The attribute data representing the attribute of each of the display data, and the processing of each of the display data to be sent to the display device is dynamically changed based on the attribute data. How to control the graphics subsystem.