JPH05122650A - Video signal recording and reproducing device with copy prevention function - Google Patents

Abstract

PURPOSE:To prevent a used tape, etc., from being copied by omitting the vertical correlation of a synchronizing signal at the time of outputting a reproducing signal and detecting the line-to-line correlation of the synchronizing signal through the use of a vertical signal processing circuit. CONSTITUTION:The device is provided with the input terminal 1 of a video signal, a horizontal synchronizing signal separating circuit (HSS) 2 separating a horizontal synchronizing signal, a vertical emphasis circuit 3 having a characteristic opposite to a vertical de-emphasis circuit provided to improve SNR at the time of reproducing, a vertical correlation detecting circuit 4 detecting the correlation in a synchronizing signal period from information in the synchronizing signal period, which is obtained from HSS 2 and the line-to-line difference of the vertical emphasis circuit 3 and a recording signal processing circuit 5 which converts the inputted video signal into a signal proper for recording and where the state of recording is controlled in accordance with the output of the vertical correlation detecting circuit 4. Then, in the case when copy prevention is necessary, the line-to-line correlation at the synchronizing signal part of a reproducing output signal is eliminated so as to detect it with the vertical recording signal processing circuit 5 of the input part of a recording system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording / reproducing apparatus with a copy protection function for preventing video signal copy in an apparatus capable of recording video signals.

[0002]

2. Description of the Related Art Conventionally, a video signal reproduced from a video signal recording / reproducing apparatus is normally displayed on the screen of a monitor in order to protect the copyrights of persons involved in the manufacture and sale of recorded media and the authors. A well-known method is one in which a satisfactory reproduced image cannot be obtained when recording is performed by another video signal recording / reproducing apparatus.

For example, V which is very popular nowadays
In the HS type VTR, there is a method of utilizing the malfunction of the automatic gain control circuit (AGC circuit) provided in the input part of the recording system of most devices. This method will be described with reference to (FIG. 6) and (FIG. 7).

In FIG. 6, 19 is an input terminal for a video signal input during recording, 20 is an AGC circuit whose gain changes according to the level of a predetermined portion of the input video signal,
Reference numeral 21 denotes a horizontal sync signal separation circuit (HS) which sets a place for level comparison in the AGC circuit 20 based on the horizontal sync signal.
S), 22 are recording signal processing circuits for performing processing suitable for recording, and 23 is an output terminal. Also, (Fig. 7) is (Fig. 6)
2 is a block diagram showing an internal configuration of the AGC circuit 20 in FIG. The circuit 28 is a variable amplifier circuit that changes the level of the video signal according to the output of the peak detection circuit 27.

In the video signal recording / reproducing apparatus having such a structure, the video signal having the copy protection measure has a pulse added in the white level direction in the vicinity of the vertical synchronizing signal. When such a video signal is input to the AGC circuit, the peak detection circuit 27 determines that the level of the video signal is very high, and the control is performed to lower the gain of the variable gain circuit 28. The signal level becomes so small that a satisfactory image cannot be obtained. Further, if the period of the white pulse added near the vertical synchronizing signal is made random, the effect is further enhanced.

[0006]

However, in the above copy protection method, an AG is added to the input section of the recording system.
It is necessary to provide a C circuit. Even if the AGC circuit is provided, if the response speed of the AGC differs depending on each device, the expected copy protection effect may not be obtained. Such differences in equipment are caused by differences in manufacturing companies and are fully conceivable. Therefore, it is impossible to realize copy protection completely in the conventional copy protection method.

In view of the above problems, the present invention provides a video signal recording / reproducing apparatus with a copy protection function, which can completely operate the copy protection function even if the input section of the recording system is not provided with an AGC circuit. It is a thing.

[0008]

In order to solve the above problems, a video signal recording / reproducing apparatus with a copy protection function according to the present invention includes a vertical emphasis circuit for performing a predetermined process on an input video signal in a vertical direction, A recording signal processing circuit for converting an output signal of the vertical emphasis circuit into a signal suitable for recording, a horizontal synchronization signal separation circuit for separating a horizontal synchronization signal from an input video signal, an output of the horizontal synchronization signal separation circuit and a vertical emphasis circuit. The difference output between the lines is input and the vertical correlation of the horizontal synchronizing signal period is detected. When there is no vertical correlation, the recording signal processing circuit is abnormally operated to detect the vertical correlation that does not satisfactorily perform recording. It is composed of a circuit.

Further, in order to prevent copying at the time of reproduction, a horizontal synchronizing signal having no correlation is added to each line.

[0010]

According to the present invention, by adopting the above configuration, the horizontal synchronizing signal, which is the same signal for all lines, becomes a different signal for each line when copy protection is desired.
That is, in the vertical emphasis circuit that performs a predetermined process in the vertical direction, the difference between the lines is detected during the synchronization signal period, and it is possible to easily prevent the recording from being performed satisfactorily.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video signal recording / reproducing apparatus with a copy protection function according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a recording system of a video signal recording / reproducing apparatus with a copy protection function of the present invention, mainly a block for detecting a copy protection signal.

In FIG. 1, 1 is an input terminal for a video signal, 2 is a horizontal sync signal separation circuit (hereinafter referred to as HSS) for separating a horizontal sync signal, and 3 is provided for improving the SNR at the time of reproduction. A vertical emphasis circuit having a reverse characteristic to the vertical de-emphasis circuit, 4 is HSS2
The vertical correlation detection circuit 5 for detecting the correlation of the synchronization signal period from the information of the synchronization signal period obtained from the above and the difference between the lines of the vertical emphasis circuit 3 converts the input video signal into a signal suitable for recording, and This is a recording signal processing circuit in which the recording state is controlled according to the output of the vertical correlation detection circuit 4.

The operation when a video signal as shown in FIG. 5 (a) is input to the video signal recording / reproducing apparatus configured as described above will be described. (Fig. 5) The signal of a is 1
A signal in which the shape of the horizontal synchronization signal changes for each line,
That is, H1 / H3 and H2 / H4 have different levels of the positive polarity portion of the horizontal synchronizing signal. The operation when such a signal is input will be described. The vertical emphasis circuit 3 is generally configured as shown in FIG. In FIG. 2, 7 is an input terminal, and 8
Is an output terminal, 10 is a delay circuit with a delay time of 1 line, 1
1 is a first adder circuit that detects the difference from the signal one line before, 12 is a coefficient circuit that performs a predetermined weighting on the difference signal between lines, 13 is the input signal, and the output signal of the coefficient circuit 12 is added The second adder circuit 9 is an output terminal from which a difference signal between lines is obtained.

In the vertical emphasis circuit 3, (FIG. 5)
When the signal shown in a is input, a differential signal between lines is detected during the period T in the horizontal synchronizing signal period, as shown in FIG. 5C. In the case of a video signal which does not require copy protection, the same signal is added to all of the periods of the horizontal synchronizing signal, and the vertical emphasis circuit 3 cannot detect a difference between lines. That is, by using the signal of (b) in FIG. 5 separated from the horizontal synchronizing signal and the differential signal between lines ((c) in FIG. 5) already obtained in the vertical emphasis circuit 3, It can be detected that the video signal needs to be copy protected.

Further, in the above description, it is assumed that the level of the positive polarity portion is changed by using the ternary synchronization signal as the horizontal synchronization signal. However, if the shape of the negative polarity portion of the ternary sync signal is not impaired, that is, if the monitor does not malfunction, the same operation can be performed if horizontal sync signals having different shapes are added between predetermined lines. It is clear that you can do it. Furthermore, the same applies to a binary synchronization signal used in NTSC or the like, instead of a ternary synchronization signal.

Further, the period in which the shape of the horizontal synchronizing signal changes is set for each line, but it is not particularly limited, and it is clear that it does not have to be set for each field / frame or for periodicity.

In the above description, the coefficient circuit 12
The same applies to the case where the input signal is simply multiplied by a predetermined value, a limiter for limiting a specific level, or a combination of a limiter and a circuit for multiplying a predetermined value. Is clear. Further, the delay amount of the delay circuit in the vertical emphasis circuit is one line, but it is obvious that the delay amount is two lines if the signal has a cycle of two lines.

Furthermore, although the signal input to the vertical correlation detection circuit is obtained from the output of the coefficient circuit, it is obvious that the same thing can be said by using the signal input to the coefficient circuit.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram of a portion for outputting a reproduction signal of a video signal recording / reproducing apparatus with a copy protection function in another embodiment.

In FIG. 3, reference numeral 14 is an input terminal for a signal reproduced from the tape / head, 15 is a reproduction signal processing circuit for performing a predetermined processing on the signal reproduced from the tape / head, and 16 is a processing during reproduction. A reference numeral 17 is a synchronizing signal generating circuit for adding a synchronizing signal to the reproduced signal, 17 is a synchronizing signal adding circuit for adding a synchronizing signal to the reproduced signal, and 18 is an output terminal for the video signal.
The reproduction signal processing circuit 15 outputs a signal as shown in (a) of FIG. When copy protection is required here, the synchronization signal generation circuit 16 outputs the synchronization signal shown in (FIG. 4) b at the timing shown in (FIG. 4) c. In this synchronizing signal, the level of the positive polarity portion changes for each line, and there is no correlation between the lines.
The sync signal adding circuit 17 switches the reproduction signal and the sync signal at a predetermined cycle and outputs the output signal shown in (d) of FIG. When copy protection is required, by outputting a sync signal with no correlation between lines,
The circuit for performing signal processing in the vertical direction provided in the input unit of the recording / reproducing apparatus on the recording side can easily perform copy protection.

[0021]

As is apparent from the above description, the video signal recording / reproducing apparatus with a copy protection function of the present invention eliminates the vertical correlation of the sync signal when the reproduction signal is output when copy protection is required. , The vertical signal processing circuit provided in the recording system is used to detect the correlation between lines of the synchronization signal. Such a configuration has an advantage that copy can be prevented easily and surely.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal recording / reproducing apparatus with a copy protection function according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the vertical emphasis circuit.

FIG. 3 is a block diagram of a reproducing system of a video signal recording / reproducing apparatus with a copy protection function according to another embodiment.

FIG. 4 is a waveform diagram of the reproduction signal.

FIG. 5 is a waveform diagram of each part of the recording system.

FIG. 6 is a block diagram of a recording system of a conventional video signal recording / reproducing apparatus.

FIG. 7 is a block diagram showing an internal configuration of an AGC circuit.

[Explanation of symbols]

 2 horizontal synchronization signal separation circuit 3 vertical emphasis circuit 4 vertical correlation detection circuit 5 recording signal processing circuit 10 delay circuit 12 coefficient circuit 15 reproduction signal processing circuit 16 synchronization signal generation circuit 17 synchronization signal addition circuit

Claims (2)

[Claims] 1. A vertical emphasis circuit for performing predetermined processing in the vertical direction on an input video signal, a recording signal processing circuit for converting an output signal of the vertical emphasis circuit into a signal suitable for recording, and the input video signal. The horizontal sync signal separation circuit for separating the horizontal sync signal from the input signal and the output of the horizontal sync signal separation circuit and the differential output between the lines of the vertical emphasis circuit are input, and the vertical correlation of the horizontal sync signal period is detected. A video signal recording / reproducing apparatus with a copy protection function, which is provided with a vertical correlation detecting circuit that does not perform recording satisfactorily by abnormally operating the recording signal processing circuit when there is no vertical correlation. 2. A video signal recording / reproducing apparatus with a copy protection function, wherein a horizontal sync signal having no correlation is added to each predetermined line when copy is prevented from being applied to an output video signal.