Cryptography – Video cryptography – Copy protection or prevention
Reexamination Certificate
1998-02-27
2002-08-06
Barron, Gilberto (Department: 2132)
Cryptography
Video cryptography
Copy protection or prevention
C380S253000, C360S060000, C369S047360, C386S349000
Reexamination Certificate
active
06430291
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and device for controlling duplication prevention of an information signal using, for example, an anti-duplication control signal recorded in a recording medium together with the information signal.
2. Description of Related Art
VTR (Video Tape Recorder) has been popularized and a lot of software for being played back on a VTR is available. Recently playback devices and recording/playback devices such as a digital VTR and DVD (Digital Video Disk) have been used practically, and pictures and sound of good quality can be played back and viewed easily.
However, on the other hand, the popularization gives rise to a problem that such abundant software is duplicated without any restriction, and heretofore various duplication prevention measures are available.
For example, though it is not a method for directly inhibiting duplication of analog video signals, a method has been available in which the difference in AGC (Auto Gain Control) system or APC (Auto Phase Control) characteristics between a recording device such as a VTR and a monitor receiver for displaying a picture is utilized to prevent duplication substantially.
In detail, a method in which a VTR performs AGC using a pseudo sync signal inserted in a video signal and a monitor receiver employs AGC system not using the pseudo sync signal is an example of the former method, and in the method, an extraordinarily high level pseudo sync signal is previously inserted as a sync signal for AGC when an analog video signal is recorded in an original recording medium, and then the extraordinarily high level pseudo sync signal is inserted in a video signal supplied from a playback VTR to a recording VTR as a sync signal for AGC.
A method utilizing the difference in APC characteristics in which the APC in a VTR follows a color burst signal in a video signal with a short time constant but the APC in a monitor receiver follows with a relatively long time constant is an example of the latter method, and in the method, the phase of a color burst signal of an video signal is previously inverted partially when analog video signals are recorded in an original recording medium, and then the video signal having the partially inverted color burst signal is output as a video signal supplied from a playback VTR to a recording VTR.
In the case described hereinabove, the monitor receiver which receives supply of the analog video signal from the playback VTR normally plays back a picture without receiving an adverse effect of the partial phase inversion of the color burst signal used for the pseudo sync signal and APC.
However, in the VTR which receives the analog video signal having the inserted pseudo sync signal described hereinabove supplied from the playback VTR or subjected to the phase inversion control of the color burst signal and records the analog video signal in a recording medium, the VTR cannot perform gain control or phase control based on the input signal, and record the video signal not normally. Therefore, a normal picture cannot be viewed when the recorded video signal is played back.
In the case which involves an analog video signal, the above-mentioned methods do not involve duplication inhibition directly, but involve duplication of an abnormal video signal, namely passive duplication prevention control.
On the other hand, in the case which involves a digital information such as a video signal, an anti-duplication control signal such as an anti-duplication code or a duplication generation restriction code is added on a video signal as a digital data and it is recorded in a recording medium in order to inhibit the duplication. This method is regarded as direct duplication prevention control.
For example,
FIG. 1
shows a basic structure of a recording device which receives a playback video signal obtained by playing back a recording medium on which a video signal having an added anti-duplication control signal is recorded as described hereinabove, and records (duplicates) the video signal in the recording medium
104
.
In the case of this recording device, the recording device receives a playback video signal on which an anti-duplication control signal is added, and the playback video signal is supplied to a write section
101
and anti-duplication control signal detection section
102
. The anti-duplication control signal detection section
102
detects the anti-duplication control signal added on the playback video signal, and supplies the detection result to a write control section
103
as duplication prevention control information.
The write control section
103
generates a control signal for controlling the write section
101
based on the supplied duplication prevention control information, and supplies it to the write section
101
.
The write section
101
converts the playback video signal to information suitable for recording and writes it in a recording medium
104
for performing recording if the control signal from the write control section
103
permits duplication. On the other hand, the write section
101
does not write the playback video signal in the recording medium
104
if the control signal from the write control section
103
inhibits duplication.
Further, if the anti-duplication control signal detected by means of the anti-duplication control signal detection section
102
permits duplication of only first generation, then the write section
101
converts the video signal to information suitable for recording and writes it in the recording medium
104
for performing recording, and also changes the anti-duplication control signal added as additional information to a duplication inhibition signal (duplication inhibition of next generation), and records it in the recording medium
104
. As the result, the video signal cannot be duplicated using the duplicated recording medium
104
.
As described hereinabove, in the case that an anti-duplication control signal is added on an information signal transmitted to a recording device, the duplication prevention control such as duplication inhibition is performed consistently in a recording medium using such an anti-duplication control signal.
However, in the case of the recording device described using
FIG. 1
, a significant lag time is required for detection processing of an anti-duplication control signal in the anti-duplication control signal detection section
102
and for generation processing of a write control signal corresponding to anti-duplication control information in the write control section
103
. Further, in the case that an anti-duplication signal is partially changed, more time is required.
From the above, some information signals are already recorded during a time period from starting of duplication, followed by detection of an anti-duplication control signal, to ending of execution of duplication prevention control corresponding to the duplication prevention control content which the detected anti-duplication control signal indicates, and as the result, some information signals are recorded and remain in a recording medium though duplication of the information signal is inhibited.
In the case that it takes, for example, several seconds from the time point of the starting of recording processing to the time point when the duplication prevention control corresponding to an anti-duplication control signal added on an information signal becomes active, it is possible to duplicate the entire information signal by way of successive partial duplication of the information signal repeatedly several seconds by several seconds though duplication of the information signal is inhibited.
A method in which a recording device is controlled so that the information signal is not recorded until the duplication prevention control corresponding to an anti-duplication control signal added on the information signal to be duplicated becomes active is considered as a remedy.
However, in this case, the information signal is not recorded in a recording medium until the duplication pr
Ikeda Nozomu
Ogino Akira
Barron Gilberto
Jack Todd
Maioli Jay H.
Sony Corporation
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