Computer graphics processing and selective visual display system – Display driving control circuitry
Reexamination Certificate
1998-11-05
2001-12-11
Nguyen, Chanh (Department: 2675)
Computer graphics processing and selective visual display system
Display driving control circuitry
C348S441000, C348S558000
Reexamination Certificate
active
06329981
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of digital electronics, and more particularly to an apparatus and method for detecting the video mode of a video signal from a graphics card.
2. Description of the Related Art
Various conventional electronic units, such as video displays or computer display units, receive and process video signals for eventual display. In a computer unit, a graphics card is typically used to generate analog video data for display on a cathode ray tube (CRT) display unit.
However, in recent years flat panel display units have been introduced in the marketplace and have gained popularity due to the many advantages of those units. For example, flat panel display units consume less power than conventional CRT display units. Flat panel display units are also relatively smaller in size and lighter in weight than CRT display units. Also, as flat panel technology improves, flat panel display units will more likely become less expensive than CRT display units. Additionally, LCD-based flat panel display units, in particular, expose users to less radiation emission than conventional CRT display units. Furthermore, unlike CRT display units, flat panel display units have no “flicker” which often causes eyestrain and headaches for many users. Moreover, unlike CRT display units that suffer from some bending and distortions near the edges of the viewable area of the CRT screen, flat panel images remain solid at the corners. The above-mentioned advantages (as well as the increasing popularity of flat panel based computer units) serve as incentives for designers to seek solutions that permit flat panel display units to replace CRT display units in desktop computer systems.
However, there are problems in integrating a computer unit with a flat panel display unit. Currently, notebook vendors use specifically designed graphic cards that output necessary control signals for driving LCD flat panel display units. In contrast, the graphic cards in conventional computer systems are not designed to generate the necessary control signals for driving LCD flat panel display units.
A video mode is defined by the timing parameters of the video signal. The timing parameters include the resolution value, the vertical timing parameters and the horizontal timing parameters, as described hereinbelow.
If a flat panel display unit is used in place of a CRT display unit in a computer system, the video mode of the video data from the computer unit must be determined so that processing circuitry can drive the flat panel display unit in order to display the video data. However, a graphics card can generate different modes. In addition, for video signals with the same resolution, different graphics cards may generate different timing parameters. Additionally, the video data from the computer graphics card must be converted into a format that is suitable for display in a flat panel unit. Thus, to integrate a flat panel display unit with a computer unit and expect both to function properly or optimally, it is necessary to detect the video mode correctly.
A prior attempt for automatically detecting the video mode of a video signal is disclosed in commonly-assigned U.S. patent application Ser. No. 08/876,846 to Biao Zhang and Jemm Yue Liang, filed Jun. 16, 1997 and entitled AUTOMATIC CLOCK RECOVERY SYSTEM FOR DISPLAY APPLICATIONS. Zhang discloses a method of detecting the video mode of a video signal based on the total number of horizontal synchronous (Hsync) pulses within one video frame. The total number of Hsync pulses within one frame of the video signal is defined as “total lines”. U.S. patent application Ser. No. 08/876,846 is fully incorporated herein by reference.
However, Zhang's approach is unable to differentiate two different video modes that both have the same number of total lines per video frame. Zhang's approach is also unable to differentiate a first video mode from a second video mode wherein the first video mode has a larger number of total lines than the second video mode and wherein the first video mode has less “active lines” per video frame than the second video mode. An active line is one that contains video information and can be displayed on a screen and seen by an end-user.
Therefore, there is a need for an apparatus and method that will automatically and accurately detect the different video modes. There is also a need for an apparatus and method for differentiating two different video modes with the same number or a substantially close number of total lines per video frame. There is also a need for an apparatus and method for differentiating between at least two modes wherein the first mode has more total lines per video frame than the second mode, but has less active lines per video frame than the second mode. There is also a need for an apparatus and method that permit a computer with a typical graphics card to function with flat panel display units.
SUMMARY OF THE INVENTION
The present invention automatically detects the video mode of video data from any graphics card in a computer unit. The video mode can be used by a subsequent processing circuit to generate appropriate control signals for sampling the analog video data. The processing circuit also performs further processing of the video data for display on a flat panel device.
The present invention provides a method of determining the resolution of video data wherein the video data is transmitted along with a plurality of synchronous signals.
The method comprises the steps of: generating, in response to the synchronous signals, a first output signal that represents the number of total lines in a frame of the video data; generating a second output signal that represents the number of active lines in a frame of the video data; and generating a signal that represents the resolution of the video data based upon the number total lines per frame and active lines per frame of the video data.
The present invention further provides an apparatus for detecting the resolution of video data. The apparatus is capable of receiving a plurality of synchronous signals along with the transmission of the video data. The apparatus comprises: a first counter stage capable of receiving the synchronous signals and generating a first counter stage output signal that represents the number of lines in a frame of the video data; a second counter stage capable of receiving an active line indicator signal that indicates an active line in the video data, the second counter stage capable of generating a second counter stage output signal that represents the number of active lines in a frame of the video data; and a logic circuit coupled to the first counter stage and to the second counter stage, the logic circuit capable of detecting the video mode of the video data based upon the values of the first counter stage output signal and the second counter stage output signal.
The present invention can accurately distinguish the video modes with the same number or a substantially close number of total lines per frame of the video data. Additionally, the present invention overcomes the prior art problem of video mode detection in the case when a first video mode has a greater number of total lines than a second video mode, but wherein the first video mode has less active lines than the second video mode.
Since the present invention enables the automatic detection of a resolution of video data, the invention allows any particular flat panel display unit to function with any one of various computer units having graphics cards that can generate different video modes with standard and non-standard timing. Thus, the end user will be able to integrate a particular flat panel display unit with any one of various computer units with less difficulty and without the need to know the particular graphics card in the user's computer unit. The end user will also be able to integrate various flat panel display units with a particular computer unit.
These, together with the various ancill
Chen Hsi-Sheng
Lin Zhihao
Bell Paul A.
NeoParadigm Labs, Inc.
Nguyen Chanh
Squire Sanders & Dempsey
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