Electrical computers and digital data processing systems: input/ – Input/output data processing – Data transfer specifying
Reexamination Certificate
1997-10-14
2001-05-29
Lee, Thomas (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Data transfer specifying
C710S035000, C713S152000, C386S349000, C386S349000, C348S086000, C455S001000
Reexamination Certificate
active
06240469
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a computer system and a motion picture transfer method and, more particularly, to a computer system having a function of decoding and reproducing digitally compressed/encoded motion picture data, and a motion picture transfer method in this system.
In recent years, with the advance in computer technology, various multimedia personal computers have been developed. A personal computer of this type can reproduce not only text data and graphics data but also motion picture data and audio data.
Generally, motion picture data is compressed and encoded in accordance with the MPEG 1, and stored in a CD (Compact Disk). The motion picture data is decoded, displayed, and reproduced using a dedicated expansion board. As an expansion board for decoding, displaying, and reproducing motion picture data, e.g., “REAL Magic” available from Sigma Designs, Inc., USA is well known. This “REAL Magic” has a video decode function complying with the MPEG 1 standard. The decoded motion picture data is synthesized with VGA graphics received from a video card via a feature connector, and the synthesized motion picture is displayed.
The MPEG 1 standard, however, assumes the use of a CD having a data transfer rate of about 1.5 Mbps. Processing motion picture data containing a large amount of image data such as a movie leads to a degradation in image quality, and the like.
Recently, a DVD (Digital Versatile Disk) has been developed as a new-generation storage medium having a data transfer rate about ten times higher than that of the CD. The DVD has a new video disk standard capable of recording video data such as a movie with a high image quality on an optical disk having the same size as that of the CD by using motion picture coding called the MPEG 2. A recording/reproducing method for the DVD is based on variable rate coding in order to ensure both the image quality and the recording time with respect to the capacity. The size of variable-rate encoded data depends on the quality of an original image. A more abruptly changing scene results in a larger data size.
When video data stored in the DVD is to be reproduced on a personal computer, the data must be read from a DVD-ROM in the main memory of the computer, and transferred to a DVD decoder. In this case, if a DVD-ROM interface and the DVD decoder are constituted as a bus master device, the motion picture data can be transferred from the DVD-ROM to the main memory, and from the main memory to the DVD decoder by using the DMA scheme, thereby reducing the load of the CPU.
Even with the DMA scheme, when motion picture data is transferred via the main memory, as described above, the same data flows through the system bus twice (data transfer from the DVD-ROM to the main memory, and data transfer from the main memory to the DVD decoder). Accordingly, the traffic of the system bus increases.
In motion picture data transfer via the main memory, if the contents of a memory area used in the motion picture data transfer are written in another device, the motion picture data read from the DVD-ROM can be illegally copied. Therefore, a copy protect measure to prevent illegal copying must be adopted.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a computer system and motion picture data transfer method capable of directly transferring motion picture data from a DVD-ROM interface to a DVD decoder without the mediacy of a main memory, and realizing a reduction in bus traffic and prevention of illegal copying.
According to the present invention, there is provided a computer system having a CPU, a system bus, and an interface connected to the system bus and allowed to control a port-addressable peripheral device for reading data from a storage medium storing digitally compressed/encoded motion picture data, comprising a motion picture decoding device connected to the system bus to decode the digitally compressed/encoded motion picture data, the motion picture decoding device including transaction control means for sending an I/O read transaction for reading the motion picture data from the interface onto the system bus, and motion picture transfer start means for starting direct transfer of the motion picture data from the interface to the motion picture decoding device, the motion picture transfer start means including first means for causing the CPU to send, to the interface, an instruction of reading motion picture data from the port-addressable peripheral device, and second means for causing the CPU to send an instruction of starting the I/O read transaction to the transaction control means.
In this computer system, since the transaction control means capable of starting the I/O read transaction is arranged in the motion picture decoding device, the motion picture decoding device can start not only a memory access transaction but also an I/O read transaction for reading motion picture data from the interface. The transfer of motion picture data from the interface to the motion picture decoding device is controlled by the motion picture transfer start means implemented by, e.g., a software driver for controlling both the interface and the motion picture decoding device. More specifically, the CPU sends, to the interface, an instruction of reading motion picture data from the port-addressable peripheral device, and an instruction of starting the I/O read transaction to the motion picture decoding device. With this processing, the motion picture data can be directly transferred from the interface to the motion picture decoding device without the mediacy of the main memory. A reduction in bus traffic and prevention of illegal copying can be realized.
As described above, according to the present invention, the motion picture data can be directly transferred from the DVD-ROM interface to the DVD decode without the mediacy of the main memory. A reduction in bus traffic and prevention of illegal copying can be realized.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
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Kabushiki Kaisha Toshiba
Lee Thomas
Perveen Rehana
Pillsbury & Winthrop LLP
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