Cryptography – Video cryptography – Copy protection or prevention
Reexamination Certificate
1999-08-27
2001-11-06
Decady, Albert (Department: 2132)
Cryptography
Video cryptography
Copy protection or prevention
C380S201000, C380S203000, C380S210000, C380S217000, C380S239000, C704S500000, C704S501000, C704S503000, C704S504000, C386S349000, C386S349000, C386S349000
Reexamination Certificate
active
06314188
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of encrypting motion picture data, and a computer system and motion picture data encoding/decoding apparatus to which this method is applied.
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 (Moving Picture Experts Group) 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 substantially 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 acceptable levels for both the image quality and the recording time with respect to the capacity. The amount of variable-rate encoded data depends on the quality of an original image. A more abruptly changing scene requires a larger amount of data.
When motion picture data stored in the DVD is to be reproduced on a personal computer, the data is read from a DVD-ROM in the main memory of the computer, and transferred to a DVD decoder. In this case, to prevent illegal copying of the data loaded in the main memory, and its illegal use, all video data included in the motion picture data must be subjected to encryption such as scramble processing.
For a recent higher-speed CPU, a so-called software decoder is desired to be realized to decode motion picture data not by dedicated hardware but by software. If the motion picture data is decoded by the software decoder, the dedicated hardware can be omitted to reduce the cost of the whole system.
However, in the use of the software decoder, the descramble processing of descrambling the scrambled motion picture data must be executed by the CPU, in addition to original processing of decoding motion picture data encoded in accordance with the MPEG 2. Since descramble processing is performed for all video data contained in the motion picture data, the load due to descramble processing on the CPU is very large. Therefore, most of the CPU power (load) is used by descramble processing, and decode processing is practically difficult to perform in real time.
As described above, since all video data is scrambled in the prior art, a large CPU power is required for descramble processing. Therefore, it is practically difficult to simultaneously satisfy the copy protect function and the software decoder.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a motion picture data encrypting method capable of preventing illegal use such as illegal display/reproduction of motion picture data by encrypting only part of the motion picture data, and simultaneously satisfying a copy protect function and a software decoder, and a computer system and motion picture data encoding/decoding apparatus to which this method is applied.
To achieve the above object, according to the present invention, there is provided a motion picture data encrypting/decrypting method of encrypting digitally compressed/encoded motion picture data containing an intraframe encoded image and an interframe predictive encoded image, thereby preventing illegal use of the motion picture data, comprising the steps of: performing scramble processing by calculating, from the digitally compressed/encoded motion picture data, the intraframe encoded image on the basis of a predetermined rule; storing the motion picture data including the intraframe encoded image having undergone the scramble processing in an optical disk as a program area of a data sequence constituted by a lead-in area, the program area, and a lead-out area, and storing a scramble rule representing a calculation rule for the scramble processing in the lead-in area; reading the motion picture data in the program area from the optical disk; and executing descramble calculation processing for the intraframe encoded image contained in the read motion picture data on the basis of scramble data, thereby decrypting the motion picture data.
In the present invention, scramble rule data representing a calculation rule for scramble processing is stored in the lead-in area of an optical disk, motion picture data is read from the program area of the optical disk, and descramble calculation processing is performed for an intraframe encoded image contained in the motion picture data on the basis of the scramble data.
According to the present invention, the intraframe encoded image within some of a plurality of packs which constitute the motion picture data is scrambled, and data representing the location of the scrambled intraframe encoded image is stored in the header portion of the motion picture data. The scrambled intraframe encoded image in some of the plurality of packets is descrambled and decoded on the basis of the intraframe encoded image location data stored in the header portion, and the scramble rule stored in the lead-in area of the optical disk.
In this motion picture data encrypting method, motion picture data digitally compressed/encoded in accordance with the MPEG 2 or the like has an intraframe encoded image (I picture), and interframe predictive encoded images (P and B pictures) based on unidirectional prediction and bidirectional prediction. The interframe predictive encoded images (P and B pictures) are decrypted using the intraframe encoded image (I picture). Since the interframe predictive encoded images (P and B pictures) cannot be correctly decrypted without the intraframe encoded image (I picture), only the intraframe encoded image (I picture) is subjected to encryption such as scramble processing. At that time, the scramble rule for scramble processing is stored in the lead-in area of the optical disk. In decryption, the scramble rule is read from the lead-in area to perform descramble, thereby decrypting the motion picture data. The contents of the lead-in area cannot be referenced to a general file system. For this reason, if the scramble rule data is stored i n the lead-in area, the scramble rule data can be protected from illegal access.
With this processing, illegal display/reproduction can be prevented by scrambling not all image data contained in the motion picture data but only part of the motion picture data. Therefore, in the use of a software decoder, the CPU power required for descramble processing can be reduced, and the motion picture data can be decoded by the software decoder in real time.
As described above, according to the present invention, illegal use such as illegal display/reproduction of the motion picture data can be prevented by encrypting only part of the motion picture data, and the copy protect function and the software decoder can be simultaneously satisfied.
Additional objects 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 inventi
Callahan Paul E.
De'cady Albert
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
LandOfFree
Motion picture data encrypting method and computer system... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motion picture data encrypting method and computer system..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motion picture data encrypting method and computer system... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2593099