JPH02266786A - System and device for video signal waveform transmission - Google Patents

Abstract

PURPOSE:To eliminate a need of transmission of synchronous information of another medium and to improve the scrambling effect by obtaining each synchronizing signal of a video signal based on conversion of the synchronizing signal. CONSTITUTION:A waveform H2 in a horizontal scanning line period includes at least one pulse waveform set in a period Ta and a reference voltage period Tr, and an amplitude B of the pulse waveform is an about middle value of an amplitude of upper and lower peak voltages of the video signal. With respect to a waveform V2 in the vertical fly-back time, a synchronizing code sequence having an amplitude C(>B) to indicate a vertical synchronizing signal is arranged in plural scanning line periods Td except the horizontal fly-back time of the normal vertical fly-back time, and a reference voltage period Te in which the voltage is equal to that in the period Tr of the waveform H2 is arranged just after the synchronizing code sequence. Thus, transmission of synchronizing information of another medium is unnecessary to improve the use efficiency of frequency, and the safety of a system is secured, and the scrambling effect is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for transmitting a waveform for a synchronizing signal and a device for transmitting the waveform among methods of scrambling video signals in pay broadcasting and the like.

Conventional technology In paid broadcasting, etc., so-called scrambling is applied in order to give only subscribers the right to restore the video and to keep the video confidential from non-subscribers. Among these, the most widely used method is one that performs some operations on the synchronization signal added to the video signal. A typical conventional example of this is suppression of synchronization signals. As shown in FIG. 2, the amplitude of the original negative synchronization pulse is reduced or eliminated to make synchronization unstable at non-participating receivers. On the other hand, synchronization information is transmitted using another transmission medium for synchronized reproduction in a subscriber's receiver. A typical example of a well-known method is
Amplitude modulation is applied to frequency-multiplexed FM audio subcarriers using synchronization information.

Problems to be Solved by the Invention The scrambling method according to the conventional example described above has the following three problems.

First, synchronization information must be transmitted using another medium for participating receivers. As mentioned above, when the amplitude of the existing FM audio subcarrier is modulated using synchronization information, no separate medium is actually used. If the carrier wave is 4-phase PSK modulation, or 1, amplitude modulation, etc. 1. i cannot be used, so another multiplexed signal is required. L-like (use of other transmission media)
I think it is a disadvantageous method from this point of view.

The second issue is the safety of the system.

What is the said another medium? This is because, once this is known, it may be relatively easy to modify non-subscribing receivers to extract synchronization information from the medium.

The third issue is the degree of confidentiality of the playback screen in non-subscribing receivers. Even if the negative sync signal is completely deleted, if the video is at a continuous high level even if the pedestal level and the brightness are small, the pedestal section will appear as if it were a negative sync signal. A situation occurs in which the synchronization becomes cloudy and the synchronization is approximately achieved (hereinafter referred to as pseudo-synchronization).

The present invention provides an advantageous system that does not require the transmission of synchronization information through a separate medium, has good frequency utilization efficiency, ensures system safety, and further improves the scrambling effect. The purpose is to

Means for Solving the Problems In order to solve the problems described above, the present invention uses a first waveform as a horizontal synchronization signal and a second waveform as a vertical synchronization signal. the first waveform includes at least one pulse waveform and a reference voltage period; transmits a video signal waveform whose amplitude is larger than that of the third waveform and includes a reference voltage period whose voltage is equal to the basic period immediately after the synchronization code sequence and its hunting sequence.

In addition to the above, the present invention transmits a video signal waveform in which the color burst signal is positioned approximately at the midpoint of the upper and lower peak voltages of the video signal.

Operation First, in the video signal waveform transmission method of the present invention, both the first waveform as a horizontal synchronizing signal and the second waveform as a vertical synchronizing signal exist within the range of the upper and lower peak values of the video signal (that is, positive polarity synchronization). Therefore, synchronization cannot be restored normally in a non-subscribing receiver that is intended for ordinary negative polarity synchronization signals. In other words, it has a scrambling effect.

Next, since the present invention does not "suppress" the synchronizing signal as in the conventional example, but "converts" the synchronizing signal, there is no need to transmit the synchronizing information using a separate medium. Therefore, it is impossible to illegally restore synchronization even if the media is known.

In addition, in the present invention, the first and second waveforms, and if necessary, the color burst signal are also positioned approximately at the center of the peak value below -J2 of the video signal, so unless images with extremely high brightness are continuous, Pseudo-synchronization has occurred.

Furthermore, in the present invention, the first waveform as the horizontal synchronization signal is
The amplitude is smaller than that of the second waveform as the vertical synchronization signal. When a reproduced screen is in a state where vertical synchronization is disrupted and a state where horizontal synchronization is disrupted, the latter is overwhelmingly more confidential. Therefore, in the present invention, the amplitude of the first waveform is reduced to make horizontal synchronization more difficult to achieve. On the other hand, in satellite transmission such as broadcasting satellites, a triangular wave with a relatively large amplitude called an energy diffusion signal is superimposed on the video signal, and if the amplitude of the synchronization signal is small, it becomes difficult for the joining receiver to detect the synchronization signal. . Therefore, the second waveform as a vertical synchronization signal, which has a small influence on confidentiality, is input with a large amplitude to reduce the detection burden on the joining receiver. The main part of this second waveform is a predetermined synchronization code sequence, and only the participating receivers are informed of this code sequence in advance.

When the subscribing receiver detects this code sequence, it clamps the input video signal using the reference voltage period provided immediately after this code sequence. This removes the influence of the triangular wave energy spread signal, and therefore the first waveform, which has a small amplitude, can be easily detected thereafter. Of course, since a reference voltage period is also provided within the second waveform, it is possible to continue the clamp operation using this period. Synchronous reproduction in the joining receiver is performed primarily by the first waveform as a horizontal synchronization signal, and the second waveform is used for field or frame detection.

In addition, in normal video signal transmission using negative polarity synchronization, approximately 30% of the total modulation degree is occupied by the synchronization signal, regardless of amplitude modulation or frequency modulation, but in the present invention, the synchronization signal is the same as the amplitude of the video signal. Since it is within this range, the degree of modulation of the video signal can be increased as a result. This makes it possible to increase the SN ratio of the demodulated video signal at the receiver.

EMBODIMENTS Below, a video signal waveform transmission system and its transmission device according to the present invention will be explained with reference to the drawings.

FIG. 1 shows the relationship between a normal video signal waveform that is not scrambled (NTSC system) and a video signal waveform of an embodiment according to the system of the present invention.
H1 is a signal waveform during a normal horizontal scanning line period of negative polarity synchronization, and H2 is a corresponding waveform during a horizontal scanning line period according to the present invention. The first waveform installed in the period Ta in the figure includes at least one pulse waveform and a reference voltage period T.
r, and the amplitude B of the pulse waveform is located approximately at the midpoint of the amplitude A of the upper and lower peak voltages of the video signal.

The joining receiver uses any changing point (rising or falling part) in this pulse waveform as the reference timing for horizontal synchronization reproduction.The color burst signal also has an amplitude of approximately A during the period Tb. The signal waveform is positioned at the median value. Therefore, the voltage in the reference voltage period Tr and the average voltage in the color burst period Tb are continuous as shown in the figure.

Further, Vl in FIG. 1(b) is a signal waveform during the vertical blanking period of a normal video signal, and V2 is a corresponding waveform during the vertical blanking period of the present invention. A synchronization code sequence to indicate a vertical synchronization signal is arranged in a plurality of scanning line periods Td excluding the horizontal retrace period of the normal vertical retrace period, and a first waveform H2 is placed immediately after the synchronization code sequence. A reference voltage period Te having the same voltage as the middle period Tr is arranged. The waveforms existing in these plural periods Td and Te correspond to the second waveform in the present invention. It is also conceivable to place a reference clock signal for assisting the detection of the synchronization code sequence at the beginning of the synchronization code sequence period (so-called preamble function). At this time, if the amplitude of the second waveform is C, the relationship between the amplitudes of the respective signal waveforms described above is A>C>B.

Next, a video signal waveform transmission device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of a video signal sending device in one embodiment of the present invention.

1 is a composite signal 1 that synthesizes a first waveform (for horizontal synchronization) and a second waveform (for vertical synchronization) in synchronization with the input video signal Va.
waveform synthesizing means 2 outputs an input video signal V according to the timing signal 1b as well as a timing signal 1c indicating the timing at which the waveform should be replaced.
This waveform replacement means replaces the horizontal and vertical synchronizing signal portions in a with the input first and second waveforms and outputs the positive synchronized video signal 2b. The operation of the video signal transmitting device configured as described above will be described below with reference to FIGS. 5 and 6.

FIG. 5 is an example of a somewhat detailed block diagram of the video signal sending device in FIG. 4. 11 is the input video signal Va
12 is a synchronization separation signal circuit that separates a synchronization signal and outputs a separated output signal t1b; 12 is a PLI that generates a reference clock 12b that is phase-synchronized with the separated output signal 11a;
The circuit 13 receives the input video signal Va from the reference clock 12b.
g) An address generation circuit that generates an address signal 13b corresponding to one field or one frame and a timing signal IC synchronized with each synchronization signal period; 14 is an address generation circuit that generates an address corresponding to the horizontal and vertical synchronization signal periods of the input video signal Va; ROM in which the information of the first and second waveforms is written respectively; 15 is a D/A converter that converts the waveform data 14b which is the output of the ROM 14 to D/A and outputs the composite signal 1b; j and 6 are timings. The gate switch is closed to the 1] side during the synchronizing signal period by the signal 1c, and to the a side during the other periods.

The amplitudes of the first and second waveforms at this time are the positive polarity synchronous video signal 2
The amplitude B of the first waveform is set to be smaller than the amplitude A of the second waveform, and the amplitude B of the first waveform is set to be smaller than the amplitude C of the second waveform, taking into consideration the tendency of the video scrambling effect. . The amplitude relationship is shown in Figures 6(a) and (b). FIG. 3 shows the procedure for synchronously regenerating the video signal waveform transmitted in this manner at the joining receiver.

Each synchronization signal of the positive polarity synchronization video signal 2b obtained in this way is not caused by conventional "suppression" but by "conversion" of the synchronization signal, so there is no need to transmit synchronization information using a separate medium, and the frequency improves the efficiency of use. , and illegal synchronization recovery when the medium is known is also difficult unless the pattern of the synchronization code sequence is known, thereby ensuring system security.

Furthermore, since the amplitude of each synchronizing signal of the positive polarity synchronous video signal 2b is set within the amplitude A of the video signal, synchronization cannot be normally reproduced in a non-subscribing receiver that targets a normal negative polarity synchronizing signal. In other words, it has a video scrambling effect.Furthermore, since the amplitude B of the first waveform as a horizontal synchronization signal is smaller than the amplitude C of the second waveform as a vertical synchronization signal, horizontal synchronization of the reproduced video is achieved. However, since the scrambling effect becomes more difficult to occur, the scrambling effect can be further improved.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is an example of a somewhat detailed block configuration diagram of the video signal waveform sending device in FIG. 4 according to the present invention. The synchronization separation circuit 11, PLL circuit 12, and D/A converter 15 have the same contents as those in FIG. 23 is an address generation circuit that generates an address signal 23b corresponding to one field or one frame of the video signal from the reference clock 12b and a timing signal IC indicating the timing of each synchronization signal period, and 24 is a horizontal and vertical synchronization circuit for the video signal Va. This is a ROM in which information on first and second waveforms and color burst signal voltage shift waveforms are written in addresses corresponding to signal periods, respectively. The difference from the configuration shown in FIG. 5 is that a synchronization signal deletion circuit 26 deletes the horizontal and vertical synchronization signals of the input video signal Va using the timing signal 1c, and a synchronization signal deletion circuit 26 that adds the synchronization pattern signal 1b and the synchronization deletion signal 28b of the synchronization signal deletion circuit 26. , a positive synchronization signal 21) is provided. The operation of the video signal waveform transmitting device configured as described above will be described below with reference to FIGS. 7 and 8.

The operation up to the attenuation generating circuit 23 is almost the same as that shown in FIG. However, the contents of the timing signal IC are slightly different. In the ROM 24, information on the first and second waveforms and the color burst voltage shift waveform is written in respective addresses corresponding to the horizontal retrace period and the vertical retrace period of the input video signal Va. 1st and 2nd at this time
The amplitude of the waveform is the same as that of the video signal 21) in the embodiment shown in FIG.
The amplitude B of the horizontal synchronization pattern signal is set to be smaller than the amplitude C of the vertical synchronization pattern in consideration of improving the video scrambling effect. D/A converter 15 is ROM
The signal of the waveform data 24b which is the output of 24 is D/A converted and a composite signal 1b as shown in FIG. 8 is output. In the composite signal j61), the median voltage portion during the period Tb is the waveform for the color burst voltage shift.

The video signal Va input to the waveform replacement means 2 is processed by a synchronization signal deletion circuit 28 to generate a timing signal IC synchronized with the video signal.
The synchronization signal is deleted, and a synchronization deletion signal 26b as shown in FIG. 8 is output. Examples of the configuration of the synchronization signal deletion circuit include a sample and hold circuit. In the adder circuit 27, this synchronization deletion signal 26b and the composite signal 1b
are added so that the first and second waveforms and the color burst signal also have potentials approximately at the median value of the amplitude A of the video signal, and the positive polarity synchronized video signal 2b is output.

In the positive synchronous video signal 2b obtained in this way, not only the horizontal and vertical synchronous parts but also the color burst signal are positioned so that they are approximately in the middle of the upper and lower peak values of the video signal, so as shown in FIG. Compared to waveform 26, pseudo-synchronization is less likely to occur, and confidentiality can be further enhanced (in waveform 2b in Figure 6, the color burst portion is near the pedestal voltage, so this is the role of negative polarity synchronization. ). Also, waveform 2 in Figure 6
In b, the negative side waveform of the color burst signal is lower than the pedestal voltage, but by setting this to the median value, it is possible to further increase the degree of modulation during transmission with respect to the original video signal.

Effects of the Invention As described above, in the present invention, each synchronization signal of a video signal is not "suppressed" as in the conventional example, but is "converted" of the synchronization signal, so there is no need to transmit synchronization information using a separate medium. Improves frequency usage efficiency. Furthermore, illegal synchronization restoration even after knowing the medium is difficult unless the pattern of the synchronization code sequence is known, thereby ensuring system safety. Furthermore, by changing this synchronization code sequence, it is possible to realize an even more secure system.

In addition, since the amplitude of each synchronization signal is set within the amplitude of the video signal, the synchronization will not be reproduced normally in a non-subscriber receiver intended for normal negative polarity synchronization signals, resulting in a video scrambling effect. . Furthermore, since the amplitude of the horizontal synchronization pattern signal is made smaller than that of the vertical synchronization pattern signal, the horizontal synchronization of the reproduced video becomes less likely to become distorted, so that the scrambling effect can be improved.

Furthermore, in the present invention, since the reference voltage period is set immediately after the synchronization signal sequence in the second waveform as the vertical synchronization signal,
The waveform is easy to clamp against DC level fluctuations caused by energy spread signals during satellite transmission. Furthermore, since all waveforms other than the video signal, including the color burst signal, are contained within the amplitude of this video signal, the entire modulation depth can be used for the video signal during modulation during transmission, and the SN in the receiving device It is possible to provide a system that is extremely advantageous in terms of ensuring ratios.

[Brief explanation of drawings]

Fig. 1 is a waveform relationship diagram between a video signal waveform according to the method of the present invention and a normal video signal waveform, Fig. 2 is a video signal waveform diagram due to synchronization suppression in the conventional method, and Fig. 3 is a procedure for synchronous reproduction of a subscriber receiver. 4 is a block diagram showing the basic configuration of the video signal waveform transmitting device of the present invention, and FIG. 5 is a block diagram showing the configuration of the first embodiment of the video signal waveform transmitting device of the present invention. Fig. 6 is a waveform diagram of each part of the first embodiment, No. 7r.
1A is a block diagram showing the configuration of a second embodiment of the video signal waveform transmitting device of the present invention, and FIG. 8 is a diagram showing operation waveforms of each part of the second embodiment. 1... Waveform synthesis means, 2... Waveform replacement means, 11.
...Synchronization separation circuit, 12...PLL circuit, 13.23
...address generation circuit, 14.24...ROM. 15...D/A converter, 16...gate switch,
26...Synchronization deletion circuit, 27...Addition circuit. Name of agent: Patent attorney Shigetaka Awasaki (1 person) (a) (b) Figure 3 Figure 4

Claims (4)

[Claims] (1) Using a first waveform as a horizontal synchronizing signal and a second waveform as a vertical synchronizing signal, both of these waveforms are located approximately at the midpoint of the upper and lower peak voltages of the corresponding video signal, and the peak voltage is , the first waveform includes at least one pulse waveform and a reference voltage period, and the second waveform has a larger amplitude than the first waveform and includes a synchronization code sequence and the above code sequence immediately after the code sequence. A video signal waveform transmission method characterized by including a reference voltage period having the same voltage as a reference voltage period. (2) The video signal waveform transmission system according to claim 1, wherein the color burst signal is positioned approximately at the midpoint of the upper and lower pixel voltages of the video signal. (3) waveform synthesis means that inputs a video signal to which a negative synchronization signal is added and outputs a composite signal including a timing signal synchronized with the video signal and the first waveform and second waveform of claim 1; The video is characterized by comprising a waveform replacement means for replacing the horizontal synchronizing signal portion of the input video signal with the first waveform and replacing the vertical synchronizing signal portion with the second waveform based on the timing signal. Signal waveform sending device. (4) The waveform replacement means includes a voltage shift function that positions the color burst signal included in the input video signal at approximately the center value of the upper and lower peak voltages of the video signal. 3. The video signal waveform transmission device according to 3.