Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-06-10
2001-10-02
Brier, Jeffery (Department: 2672)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S501000, C345S504000
Reexamination Certificate
active
06297794
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a computer system having a ZV (Zoomed Video) port and also to a method of switching video sources to be transferred by using a ZV port.
BACKGROUND ART
In recent years, notebook-type personal computers have been used in increasing numbers, each having a PC card socket which accords with the standards of PCMCIA (Personal Computer Memory Card International Association), an American association, and with the standards of JEIDA. Various techniques have been developed to use this PC card as a video capture card or an MPEG decoder card, for controlling the input and output of motion-picture data.
System architecture having a PCI local bus is now used increasingly in order to process a great amount of data, such as motion-picture data, with high efficiency. This is because the PCI local bus can transfer data at high speed.
If the PCI local bus is used, however, its data-transferring ability is limited. The data-transferring ability of the PCI local bus is insufficient when the PC card is used as a video capture card or an MPEG decoder card as is mentioned above.
Recently, a technique has been developed. The technique is to connect a PC card and a display controller directly, by a so-called ZV (Zoomed Video) port, which is a bus designed exclusively for transferring motion-picture data. The ZV port enables the PC card to output video/audio data directly to the display controller/audio controller, without using the system bus. This solves the problem that the system bus is occupied for a long time to transfer a great amount of video data, thereby enhancing the video-data processing ability of the system.
Recently, multimedia techniques have advanced also in the field of personal computers. Various devices other than PC cards, which handle motion-picture data, are now incorporated in the system. These devices will be exemplified as follows:
(1) Video capture: Converting analog video signals from an imaging device such as a video camera to digital data, and inputting the digital data.
(2) MPEG decoder: Expanding motion-picture data compressed by MPEG, thus generating live motion-picture data.
(3) High-speed serial interface, e.g. IEEE1394: Inputting motion-picture data transferred from a digital video camera, a digital video player, and the like.
These devices are connected to the system bus in most cases. Therefore, the motion-picture data output from these devices will be transferred to the display controller through the system bus.
(1) Usually, the system bus has a bandwidth large enough to transfer motion-picture data. The rate of transferring motion-picture data must therefore be lowered in order to transfer motion-picture data through the system bus. If the transfer rate is lowered, the resolution of the motion picture will decrease, the frame rate thereof will decrease, or the number of bits per pixel will decrease. Consequently, the motion picture will be deteriorated in quality.
(2) The motion-picture data transfer mostly occupies the bandwidth of the system bus. The operations other than the motion-picture transfer via the system bus, for example the data transfer between the device and a disk drive will become slow. Further, the device may not normally operate, failing to transfer data in real-time fashion. If a communication device such as a modem does not operate normally, for example, a part of data may not be transmitted.
DISCLOSURE OF INVENTION
The present invention has been made in view of the foregoing. Its object is to provide a computer system in which a plurality of video sources can be transferred directly to the display controller, without using the system bus, from a plurality of devices which process motion-picture data, so that the various video sources can be displayed with high efficiency, and also to provide a method of switching video sources in the system.
The present invention is a computer system having a display controller having a video port for receiving motion-picture data and capable of displaying the motion-picture data input to the video port, and a motion-picture data bus provided for transferring exclusively the motion-picture data to the video port of the display controller. The computer system is characterized by comprising a plurality of video devices and switching means. The video devices process different motion-picture sources, each having an output port connected to the motion-picture data bus and designed to output motion-picture data from the output port to the motion-picture data bus. The switching means switches the video devices, thereby selecting one video device which is to transfer motion-picture data to the display controller through the motion-picture data bus.
In the computer system, the video devices, such as a video capture, an MPEG decoder, and an IEEE1394 serial interface, are connected to a video/audio dedicated bus provided for transferring motion-picture data directly to the video port (ZV port) of the display controller, without using the system bus. Thus, one and the same video/audio dedicated bus is used to transfer motion-picture data from whichever video device. Therefore, whichever video source can be transferred to the display controller, without using the system bus. The various video sources can be transferred with high efficiency. Furthermore, the computer system has switching means for switching the video devices which use the video/audio dedicated bus. The switching means operates such that motion-picture data is transferred to the display controller from only one device at a time. This makes it possible for the single video/audio dedicated bus to connect the devices to the display controller in a point-to-point fashion. Data collision on the video/audio dedicated bus can thereby be prevented.
The means for switching the video devices, thus enabling one device at a time to use the video/audio dedicated bus, preferably has one of the following alternative structures:
(1) Each video device has an output buffer for outputting motion-picture data from the output port to the video/audio dedicated bus. Each video device also has means for enabling or disabling the output buffer to output the data, in accordance with an instruction supplied from the CPU of the computer system.
Each video device therefore outputs motion-picture data to the video/audio dedicated bus only when the CPU issues a motion-picture data transfer instruction or the like. Software executed by the CPU enables the output buffer of only one video device, at a time, to output data. Data collision on the video/audio dedicated bus can therefore be prevented easily.
(2) The video devices are connected to the video/audio dedicated bus, forming a daisy chain. A control signal line is added for transferring an enable signal which allows each video device to use the video/audio dedicated bus, to the video devices, one after another, first from the video device which located at the head of the daisy chain.
Each video device has an output buffer for outputting motion-picture data from the output port to the video/audio dedicated bus. Each video device also has means for enabling or disabling the output buffer to output the data, in accordance with an instruction supplied from the CPU of the computer system and the enable signal transferred through the control signal line. The means inhibits the transfer of the enable signal to the next video device when the output buffer is enabled to output the motion-picture data.
In this structure, any video device has priority over the video device located downstream of the daisy chain, with regard to the use of the video/audio dedicated bus. No enable signal is transferred to the video device located downstream of the daisy chain before the audio device enabled to use the video/audio dedicated bus finishes using the video/audio dedicated bus. Thus, automatic control is achieved that the output buffer of only one device is allowed, at a time, to output data. Software control is unnecessary to allow, at a time, the output buffer of only one device to output data.
(3) A plur
Honma Toru
Nishigaki Nobutaka
Sakai Makoto
Tsubouchi Takumi
Brier Jeffery
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Good-Johnson Motilewa
Kabushiki Kaisha Toshiba
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