Video signal transmission device, video signal output...

Television – Format

Reexamination Certificate

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Details

C348S465000, C380S201000, C380S203000, C380S268000, C380S255000, C386S349000, C375S130000

Reexamination Certificate

active

06195129

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an image duplication control system for playing back a video signal recorded on a recording medium, and limiting or preventing the reproduced video signal from being played back and recorded on another recording medium. It also relates to an image playback device, image recording device and image recording medium on which a video signal is recorded which use this image duplication control system.
VTR (Video Tape recording devices) has been popularized in daily life, and many kinds of software which can be played back on a VTR are supplied abundantly. Digital VTR or DVD (Digital Video Disks) playback devices have been available practically now, and provide images and sound of exceptionally high quality.
There is, however, a problem in that this great abundance of software can be copied without restriction, and several methods have already been proposed to inhibit duplication.
For example, for a VTR which outputs an analog video signal, one method to prevent copying uses a difference in the AGC (Automatic Gain Control) system, or in the APC (Automatic Phase Control) system, of the VTR recording device and of a monitor receiver which displays the image.
When the VTR employs AGC using a pseudo sync signal inserted in the video signal, a monitor receiver employs AGC which does not use this pseudo sync signal. In this anti-duplication method using a difference in the type of AGC, a very high level pseudo sync signal is inserted and output in the video signal supplied from the playback VTR to the recording VTR as an AGC sync signal.
When the VTR employs APC using the phase of a color burst in the video signal, the monitor receiver uses a different type of APC. In an anti-duplication method using a difference in the type of APC, the phase of the color burst in the video signal supplied from the playback VTR to the recording VTR is partially inverted.
The monitor receiver which receives the analog video signal from the playback VTR plays back the image correctly without being affected by the high level pseudo sync signal in AGC or the partial phase inversion of the color burst signal in APC.
On the other hand, when a VTR records, on a recording medium, the analog video signal into which pseudo sync signals have been inserted or the analog video signal which has been subjected to color burst signal phase inverting control in the playback VTR as described herein above, proper gain control or phase control based on the input signal cannot be performed, and so the video signal is not correctly recorded. Even if this signal is played back, therefore, normal picture and sound cannot be obtained.
In the case of a digitized video signal, for example, in a digital VTR, an anti-duplication signal or an anti-duplication control signal comprising, for example, a duplication ranking control code, is added as digital data to the video signal and recorded on the recording medium, so as to prevent or control duplication of the image.
In this case, the playback digital VTR reads the video signal, audio signal and anti-duplication control signal, and supplies them as digital or analog data to a recording digital VTR.
In the digital VTR being used as a recording device, the anti-duplication control signal is extracted from the supplied playback signal, and recording of the playback signal is then controlled based on the anti-duplication control signal. For example, when the anti-duplication control signal comprises an anti-duplication signal, the recording VTR does not perform recording.
Alternatively, when the anti-duplication control signal comprises a copy ranking control code, recording is controlled by this ranking control code. For example, when the copy ranking code limits duplication to one copy, the digital VTR used for recording adds this anti-duplication code before recording the video signal and audio signal on the recording medium as digital data. It is thereinafter impossible to duplicate the video signal from the copy.
Hence, in the case of a digital connection when the video signal, the audio signal, and the anti-duplication control signal used as digital signals are supplied to the digital VTR used as a recording device, anti-duplication control is performed on the recording side using the anti-duplication control signal by supplying this signal to the digital VTR as digital data.
However, in the case of an analog connection where the video signal and audio signal are supplied as analog signals, the anti-duplication control signal is lost when the signal supplied to the recording device is D/A converted. Hence, in the case of an analog connection, an anti-duplication control signal must be added to the D/A converted image or sound signal, and this causes deterioration of the video signal and audio signal.
It is, therefore, difficult to add an anti-duplication control signal and to extract it in the recorder for the purpose of anti-duplication control, without causing deterioration of the D/A converted video signal or audio signal.
Conventionally, therefore, in the case of an analog connection, duplication was prevented by an anti-duplication method using a difference in the AGC, or a difference in APC characteristics, between the VTR and the monitor receiver as described herein above.
However, in some cases, when anti-duplication is prevented using the above-mentioned difference in the AGC or a difference in APC characteristics between the VTR and the monitor receiver, depending on the type of AGC or APC characteristics on the recording side, the video signal may nevertheless be correctly recorded. In this case, it might happen that duplication cannot be prevented, or that the reproduced image on the monitor receiver is distorted. Further, it was troublesome to change over the anti-duplication method depending on whether there was an analog connection or a digital connection.
The inventors have already proposed an anti-duplication method in which a spectrally spread anti-duplication control signal is superimposed ona video signal (U.S. patent application No. 08175510). This method may be used for both digital connections and analog connections, and it causes no deterioration of the image or sound which is played back.
According to this method, when the original recording medium is fabricated, a PN (Pseudorandom Noise) sequence code (referred to hereinafter as PN code) used as a spreading code is generated with a sufficiently short period and spectrally spread by multiplying it by the anti-duplication control signal. In this way, a narrow bandwidth, high level anti-duplication control signal is converted to a wideband, low level signal which does not affect the video signal or sound signal. This spectrally spread anti-duplication control signal is then superimposed on the video signal supplied to the recording medium, and recorded.
On the other hand, in the recording side, a PN code is generated at the same timing and phase as the PN code used for spectral spreading in the playback device relative to the video signal supplied by the playback device. The generated PN code is multiplied by the video signal on which the anti-duplication control signal is superimposed so as to extract the original anti-duplication control signal, that is, so as to perform inversion spectral spreading. Anti-duplication is then controlled based on the anti-duplication control signal extracted by inversion spectral spreading.
In this way, the anti-duplication control signal is spectrally spread and superimposed on the video signal as a wideband, low level signal in the playback device. It is therefore difficult for a person who wishes to illegally duplicate the video signal, to remove the anti-duplication control signal which is superimposed on it.
However, it is possible for a person who wants to prevent illegal duplication to detect the superimposed anti-duplication control signal by inversion spectral spreading, and use it. This anti-duplication control signal is therefore supplied to the recording device together with the video signal. In the recording s

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