Computer graphics processing and selective visual display system – Plural display systems
Reexamination Certificate
1998-12-21
2002-12-03
Hjerpe, Richard (Department: 2774)
Computer graphics processing and selective visual display system
Plural display systems
Reexamination Certificate
active
06489933
ABSTRACT:
BACKGROUND OF THE INVENTION
This application is based on Japanese Patent Application No. 9-355439 filed Dec. 24, 1997, the content of which is incorporated herein by reference.
The present invention relates to a display controller and a computer system using the same and, more particularly, to a display controller having a motion picture display function, computer system, and motion picture display control method.
In recent years, along with the development of computers and multimedia techniques, various kinds of so-called multimedia compatible personal computers have been developed. A personal computer of this type has a function of reproducing motion pictures and audio data in addition to text and graphics data.
With the advent of such multimedia computers, a DVD has received a lot of attention as an alternative storage medium to a CD-ROM. A single DVD-ROM medium can record data of about 4.7 Gbytes about seven times the capacity of the existing CD-ROM on one side, and can record data of about 9.4 Gbytes in case of two-sided recording. Using such DVD-ROM media, titles such as movies including a large volume of video information can be reproduced with high quality on the personal computer.
Video information recorded on a DVD-ROM medium consists of two kinds of data, i.e., presentation data and navigation data. The presentation data is a set of video objects to be reproduced, and consists of video, subpicture, and audio data. The video data is compressed and coded by MPEG2. As the coding schemes of subpicture and audio data, runlength coding, DOLBY DIGITAL, and the like are supported. The subpicture data is bitmap data, and is used for displaying superimposed dialogues of a movie, selection items on a menu window, and the like. One video object can contain video data for one channel, audio data for a maximum of eight channels, and subpicture data for a maximum of 32 channels.
The navigation data is reproduction control data for controlling the reproduction sequence of the presentation data, and navigation commands can be embedded in this data. The navigation commands are used for changing the reproduction contents or order of video data. Using the navigation commands, a title creator can define various branch structures in his or her title, and can create an interactive title.
When a motion picture title stored in a DVD is reproduced on a personal computer, an encoded stream of motion picture data is loaded from a DVD drive into the main memory of the personal computer, and the loaded stream is transferred to an MPEG2 decoder. The MPEG2 decoder descrambles the encoded stream, which has been scrambled to prevent the title from being illicitly copied, and then decodes to expand the encoded stream. The decoded motion picture data is sent to a display controller (VGA controller) for controlling the display monitor of the personal computer. The motion picture data sent to the VGA controller is temporarily written in a video RAM like normal graphics data provided by an OS or an application program, and is then displayed on the screen of the display monitor or a TV.
However, the motion picture data stored in the DVD is created based on TV video signals of, e.g., the NTSC scheme as in a home TV, and the vertical sync frequency of the motion picture data decoded by the MPEG2 decoder is normally 60 Hz (60 fields/sec). By contrast, the VGA controller is designed to display at a dedicated refresh rate (60 Hz, 72 Hz, 75 Hz, or the like) for controlling a sequential scan display monitor. The refresh rate used is determined by the screen resolution or the like of the display monitor. Note that the refresh rate represents the number of fields to be refreshed per second, and the quality of the display screen can be improved as the refresh rate becomes higher. Normally, a refresh rate of at least 60 Hz or more is required (in a non-interlace mode) to avoid the human eyes from feeling flickering.
Hence, when the motion picture data is displayed via the VGA controller, the vertical sync frequency of the motion picture data written in the video RAM is often different from the refresh rate for screen display. In such case, so-called “tearing” occurs, i.e., a horizontal line seems to scroll from the top to bottom or vice versa on the display screen. The “tearing” is produced as follows.
For example, assume that the vertical sync frequency of the motion picture data is 60 Hz (60 fields/sec), and the refresh rate for screen display is set at 75 Hz. In this case, the field image of the motion picture on the video RAM is refreshed 60 times per sec by writing the motion picture data, while the number of fields to be read out from the video RAM to refresh the screen is 75 per sec. Hence, a field image in the middle of being rewritten on the video RAM is read out, and is displayed as the next field, thus causing the above-mentioned “tearing”.
Also, since the motion picture data premised on a display on a home TV and computer graphics data have different color spaces, signal bands, scan schemes, and the like, the VGA controller must convert the color space of the motion picture data from YUV into RGB for computer graphics, and must perform other conversion processes such as conversion of the signal band (conversion of the dynamic range), conversion from the interlace mode to the non-interlace mode, and the like. Conventionally, independently of the display monitor or TV on which the motion picture data is to be displayed, the motion picture data is temporarily written in the video RAM. Hence, such conversion processes are performed not only when the motion picture data is displayed on the display monitor of the computer, but also when it is displayed on the TV. For this reason, when the motion picture data is displayed on the TV via the VGA controller, the displayed image is inferior to the original image as a result of various conversion processes.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a display controller, computer system, and motion picture display control method, which can prevent the above-mentioned “tearing” and deterioration of image quality that may take place when motion picture data is displayed on a TV, and can display motion picture data such as a DVD title and the like with high quality.
In order to achieve the above object, according to the present invention, there is provided a display controller which can display an image on a display monitor of a computer having an image memory or a TV, comprising: a port for externally inputting motion picture data; and refresh rate control means for matching a refresh rate used for displaying the motion picture data input from the port on a screen of the display monitor or TV with a vertical sync frequency of the motion picture data input from the port.
According to this display controller, when motion picture data is input from the port, the refresh rate is automatically changed in correspondence with the vertical sync frequency of that motion picture data. As a result, the number of field images of a motion picture to be refreshed per second by writing motion picture data in the image memory can be matched with the number of fields to be read out from the image memory and displayed per second for refreshing the screen, thus preventing the above-mentioned “tearing”. Hence, even when motion picture data is temporarily written in the image memory and is then displayed on the display monitor, the user can observe a high-quality image free from “tearing”.
Since the refresh rate is changed in correspondence with the vertical sync frequency of the motion picture data, the horizontal/vertical sync signals of the motion picture data input from the port can be used as those for displaying on the display monitor or TV. Since the horizontal/vertical sync signals of the motion picture data input from the port are used as those for displaying on the display monitor or TV, mapping of motion picture data on the image memory can be perfectly synchronized with refreshing. More specifically, even when the refresh rate is concor
Ishibashi Yasuhiro
Zenda Hiroki
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Laneau Ronald
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