Cryptography – Video cryptography – Copy protection or prevention
Reexamination Certificate
1999-02-05
2001-07-03
Cangialosi, Salvatore (Department: 2661)
Cryptography
Video cryptography
Copy protection or prevention
C380S204000
Reexamination Certificate
active
06256390
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a devise-having a digital-interface having a copy protection function and a network system using such a device and a copy protection method.
BACKGROUND OF THE INVENTION
Recently, digitalization of audio and visual processing has become wide spread. A DVC (Digital Video Cassette Recorder) for digital recording and reproduction is also being developed. Digitalization prevents noises from entering the transmission and recording so that the signal quality is improved. In such digital recording, the original can be completely exactly duplicated. It is, however, desirable to protect the copyright of information recorded on the recording media.
In particular, provisions for copyright protection of animation images including sound data are being specified by the organizations concerned. They include the VHRA (Video Home Recording Act), which has been proposed in Japan and is currently being discussed in the United States. The VHRA specifies that the analog connection using analog devices as sources shall adopt the macro-vision method or CGMS-A (Copy Generation Management System-Analog) method, and that the analog connection using digital devices as sources shall adopt the macro-vision method, and that the digital connection using digital devices as sources shall adopt the CGMS-A (Copy Generation Management System-Analog) method or the CGMS-D (Copy Generation Management System-Digital) method.
The macro-vision method used in the analog connection overlays the copy guard signal during the vertical flyback time of the video signal to make normal recording difficult. That is, this method changes the synchronous signal level of the image to make the synchronous detection by a recording device impossible and also changes the burst phase to make the normal color reproduction by a recording device difficult. Thus, the image signal with overlaid copy guard signals prevents normal image recording without any particular procedure by a recording device.
In addition, the CGMS-A method inserts a flag to indicate whether the data can be copied or not in a predetermined horizontal period during the vertical flyback time of the video signal, and the recording device controls its recording according to the flag.
The CGMS-D method used in the digital connection adds a two-bit copy generation management information to the recording format or the digital interface format (data format for transmission) peculiar to devices such as digital VCRs and DVDs. Reproduction devices always insert a copy generation management information into the output signal and recording devices detect the copy generation management information from the input signal to control recording.
The copy generation management information indicates that copying is prohibited with “11”, and that copying is allowed only once with “10”, and that copying can be made freely with “00”. When the copy generation management information contained in the input signal is “10”, recording devices record the input signal and change the copy generation management information to “11” (copy prohibition) during recording. This means that the signal cannot be copied again.
For the digital VCR (hereinafter also referred to as DVC), the Consumer Digital VCR Association of Japan established SD (Standard-Definition) Standards corresponding to the NTSC or PAL standards and HD (High Definition) Standards corresponding to the high definition TV. These SD and HD standards (hereinafter collectively referred to as DVC standards) already have provisions about the recording format and the digital interface format for the copy generation management information in the DVC. That is, for both of the recording format and the digital interface format, the copy generation management information is inserted in the source control packet in the VAUX area to be described later.
In addition to the DVC standard, it is specified that the copy generation management information will be inserted in the header of the MPEG2 transport stream. However, other standards do not consider CGMS-D, and have no provision for where in the packet or interface format of various digital signals and devices the copy generation management information shall be inserted.
According to the standard currently under discussion by the IEC (International Electrotechnical Committee), a device handling various images will record the copy generation management information in its recording digital data and will output the digital interface output including the copy generation management information in data reproduction. In addition, it is specified that a recording device to record such interface output will detect the copy generation management information and record the data corresponding to it.
Meanwhile, network systems have been recently developing with the progress of multimedia. The multimedia technology requires not only data transmission between personal computers, but also data transmission with audio and video devices (hereinafter referred to as AV devices).
For this purpose, a unified standard of digital interface method for data transmission between a computer and a digital image device is being studied. As a low-cost peripheral interface suitable for multimedia application, IEEE (The Institute of Electrical and Electronics Engineers, Inc.) 1394 is most likely to be adopted.
IEEE 1394 enables multiple data transmission for a plurality of channels. In addition, IEEE 1394 has an isochronous transmission function to ensure transmission of video and sound data in a specified time and is considered to be a digital interface suitable for image transmission.
For IEEE 1394, detailed commands are currently specified in DVB-WG (for European digital broadcasting) of the Digital VCR Association, R4.1 of EIA discussing DTV (Digital TV) decoder in the U.S., and IEEE 1394 T.A. (Trade Association). IEEE 1394 is originally based on computer technologies, but since it is capable of synchronous communication, audio and video equipment manufacturers are also working for standardization. The proposal from the Digital VCR Association is also discussed in 1394TA.
Detailed contents of IEEE 1394 are described in an article entitled “Comparison of Three New Interfaces Searching for the Post-SCSI Design Concept” on pp. 152 to 163 of Nikkei Electronics (No. 612, dated Jul. 4, 1994) (Literature 1). IEEE 1394 is also described in detail in the Japanese Patent Application Laid-open No. Heisei 8-279818.
IEEE 1394 enables multiple-transmission for a plurality of channels and achieves transmission of video data from a plurality of devices, using a plurality of channels assigned to the isochronous packet. For the digital interface of IEEE 1394, however, no rule about copy protection is specified. According to IEEE 1394, the data in the digital interface format of various devices such as DVC transmission format (hereinafter referred to as D-interface format) and MPEG2 transport packet, are just transmitted with format conversion.
Therefore, when data are transmitted using IEEE 1394 to copy an image, the recording device fetches data from the data flowing in the bus of IEEE 1394, and restores the fetched data to the digital interface format peculiar to the reproduction device, and then, extracts the inserted copy generation management information. The copy generation management information is obtained by detecting the insertion position of the copy generation management information with its digital interface processing section or recorded and reproduced data processing sections, such as an error correction circuit. For example, when the transmitted data is DVC data, copying is controlled according to whether the predetermined 2-bit data in the source control packet in VAUX is “11” or “10” or “00”.
FIG. 1
is a block diagram showing a device having a digital interface according to IEEE 1394 standard.
FIGS. 2 and 3
illustrate the D-interface format and MPEG2 transport stream, respectively.
Reproduction (sending) devices
1
and
2
are DVC and DVD, respectively. These reproduction dev
Endoh Kenjiro
Okuyama Takehiko
Shimoda Kenji
Cangialosi Salvatore
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
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