JPS59216389A - Video signal transmission system - Google Patents

Abstract

PURPOSE:To have a sufficient secrecy and restore a high-quality video signal by inverting the polarity of a composite video signal including a horizontal synchronizing signal in every scanning line unit in the transmission side in the video signal transmission of chargeable television broadcasting. CONSTITUTION:A scrambling circuit 9 switches outputs of an inverting amplifier 6 and a non-inverting amplifier 7 by a switching signal 102 to transmit a scramble signal where the polarity is inverted in the back porch part of the horizontal synchronizing signal. A vertical synchronizing signal separating circuit 11 of a switching signal generating circuit 15 transmits a start pulse synchronized with the horizontal synchronizing signal to a pulse signal generator 12. The generator 12 generates a pulse signal having the frequency of the horizontal synchronizing signal which is a certain time behind the start pulse, and this pulse signal is inputted to the clock input of a PN code generator 13, and the PN code designated by a key code setter 14 is transmitted as the switching signal 102 to the circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal transmission method, in particular, to a video signal transmission system in which a television video signal is transmitted with its polarity inverted using a pseudo-random code (PN code is abbreviated) in units of horizontal scanning periods, and the video signal is restored and played back on the receiving side. Regarding signal transmission methods.

In paid television program distribution using satellites and paid television broadcasting by cable or wireless, waveform conversion processing is performed to make the television video signal so that it cannot be easily received by ordinary receiving equipment. There is a need for a transmission method that can restore this and produce high-quality images. As this type of transmission system, several basic processing methods and a composite processing method that combines these methods are already known.

As a basic processing method that is relatively easy to process, there is a method in which the polarity of the black and white level of the video signal is inverted with respect to the intermediate gray level and transmitted. There are several ways to transmit the temperature. In these conventional polarity inversion methods, the horizontal synchronization signal and the video signal, which are normally used as the reference level during DC component reproduction, are processed separately, so the inversion reference level may fluctuate due to DC drift in the inversion processing circuit, Due to the difference in the reference level between the transmitting side that performs inversion processing and the receiving side that performs restoration processing, a level difference occurs in the restored video signal, and when inversion processing is performed on a scanning line basis, striped shading occurs in the image. However, the disadvantage is that high-quality images cannot be reproduced stably.

An object of the present invention is to invert the polarity of a composite video signal including a horizontal synchronization signal in units of scanning lines, thereby stably obtaining a restored signal with sufficient confidentiality and good quality with a simple polarity inversion operation. An object of the present invention is to provide a video signal transmission system in which the drawbacks of the above are eliminated.

The video signal transmission method of the present invention is a video signal transmission method in which a television video signal is subjected to waveform conversion processing in a video processing unit on the transmitting side, and then restored in a restoration processing unit on the receiving side to reproduce the original signal. The video processing unit on the transmitting side inverts the composite image signal 1 including the horizontal synchronization signal according to a PN code in which the horizontal scanning frequency is at least clockwise. The value is transmitted with polarity inverted as shown in 4 to the bottom, and the restoration processing section of t(11) flips the polarity of the composite image i&fN according to the PN code and inverts the polarity. It is constructed by adding 4+iii clamp means for controlling 18 of the same polarity to r=J-value.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the transmission 91I video processing section of the present invention, and FIG. 2 is a block diagram of an embodiment of the corresponding reception (III restoration processing section). The processing section includes a known feedback compression type clamp circuit 5 consisting of a differential amplifier 1, a sample hold circuit 2, a composite synchronous separation circuit 3, and a low-pass filter 4, and an inverting amplifier 6 connected to the output thereof and a non-inverting amplifier 7. , and a non-inverting amplifier 10 that slowly amplifies the scrambled output and transmits it to the C output terminal 101.
Rope surface synchronous separation circuit 11. Pulse signal generator 12. A switching device (which is composed of a PN code generator 13 + a key code setter 14 and generates a switching signal 102 for controlling the scrambling circuit 9)
11'♂) is formed from the No. 8 generation circuit 15. The composite video signal from the input terminal 100 has its DC level set by the clamp circuit 5 and is sent to the scramble circuit 9. The scramble circuit 9 is a switching signal 1 synchronized with the horizontal synchronization signal 18.
By switching the outputs of the inverting amplifier 6 and the non-inverting amplifier 7 by 02, a scramble signal whose polarity is inverted at the back porch portion of the horizontal synchronizing signal is sent out as shown in FIG. 3(a). The DC voltages of the inverting amplifier 6 and the non-inverting amplifier 7 are set so that the white level A of the inverted video signal slightly exceeds the peak value B of the non-inverted horizontal synchronizing signal. In the synchronization detection circuit of the formula, the horizontal synchronization is disturbed by the video signal of the inversion section, so in addition to the inversion effect of the video signal, a sufficient concealment effect is obtained and it is possible to distinguish the video of the original signal before being scrambled. I won't be able to do that. The vertical synchronization separation circuit 13 of the switching signal generation circuit 15 separates the vertical synchronization signal from the output of the composite synchronization separation circuit 3, and calculates the number of equalization pulses and horizontal synchronization signals sent following the vertical synchronization signal. is counted, and a start pulse synchronized with the first horizontal synchronizing signal is sent to the pulse signal generator 12. The pulse signal generator 12 has an oscillator with a stable frequency, and generates a pulse signal of the horizontal synchronization No. 1 frequency V delayed by a certain period of time from the start pulse. This signal becomes the clock input of the PN code generator 13, and the 1
The PN code specified by the 4-digit 0-digit key code setter 14 is sent to the scrambling circuit 9 as a switching signal 102, and the polarity is inverted at the back porch portion of the horizontal synchronizing signal as shown in FIG. 3(a). The pulse signal generator 12vi counter is installed, and the signal transmission is stopped when the number of generated pulses is counted per house, and the transmission is started again with the start pulse from the vertical synchronization separation circuit 11.
Therefore, the inversion operation by the scramble circuit 9 is limited to only the video signal period, and the vertical synchronizing signal including the equalization pulse is transmitted as is. Even if the frequency of the pulse signal generated by the synchronization signal generator 120 and the frequency of the horizontal synchronization signal do not completely match, the structure is configured to synchronize with each vertical synchronization signal, so the phase that occurs between one field The deviation of -C is slight and does not interfere with the inversion operation of the scramble circuit 90.

The restoration processing section shown in FIG. 2 amplifies the inverted scramble signal from the input terminal 103, and the feedback voltage
4, a non-inverting amplifier 10' connected to its output and transmitting to the scramble terminal 105, generates the same PN code as that on the transmitting side based on the vertical synchronization signal of the received signal. Switching signal generation circuit 15'
, a composite synchronous PIIF circuit 3b, and a sample hold circuit 2a and 2b.

FET switch Bb, differential amplifier 17. Low pass filter 4
A and a feedback circuit 18 that generates a feedback voltage 104. The third signal added to the input terminal 103
The scramble key signal as shown in FIG. 3(a) passes through a differential amplifier 16, and similarly to the scramble circuit 9, an inverting amplifier 5a and a non-inverting amplifier 7a.

A descrambling circuit 91 consisting of an FET switch 8a restores the signals to signals of the same polarity as shown in FIG. 3(b). The inversion reference level of the descrambling circuit 9' is shown in FIG. 3(a).
If they do not match the intermediate values of the inverted and non-inverted horizontal synchronizing signal peak values shown as C, the horizontal synchronizing signal peak values of the reconstructed signal are, for example, B' and A in FIG. 3(b). ′ does not match. If you try to make them match, B' will decrease and A' will increase, and at D they will match. Conversely, if B' is lower than A', control may be performed to increase the DC component of the input signal. In the circuit shown in FIG. 2, the output of the initial synchronization separation circuit 3b is switched by the F E 'l' switch 8b in synchronization with the inversion operation of the descrambling circuit 9', and the sampling synchronization pulse of the two sample and hold circuits 2a and 2b is By doing so, the peak envelope value B' of the inverted horizontal synchronizing signal and the peak envelope value B' of the horizontal synchronizing signal that has not been inverted are detected, and the difference is calculated by the differential amplifier 17.
This is realized by feeding back to the differential amplifier 16 through the entire low-pass filter 4a. Switching signal generation circuit 1
Similarly to the switching signal generation circuit 15 on the transmission side, 5' is a composite sync separation circuit 3a, a vertical sync separation circuit 11a, a pulse signal generator 12, an N code generator 13a, a key code setter 14a, and a transmitter. 9111 P The same 1'N code as the N code is generated, and the FET switches 8a and 13b
control at the same time.

As explained above, this feedback circuit controls the peak value of the horizontal synchronization signal of the TTU source information so that it matches the peak value of the horizontal synchronization signal, and the relationship between the video signal and the horizontal synchronization signal is controlled by the inversion operation.
Since there is no distortion, the correct composite video signal can be reproduced and a high-quality image can be obtained.

In the explanation of the above embodiment, it was explained that the white level of the video signal inverted by the video processing unit of the C1 transmission 11111 is inverted so as to exceed the peak value of the horizontal synchronization signal that is not inverted, but if both levels are equal or slightly white, Even if the level is lowered or lowered, the effect of disturbing horizontal synchronization when received with a normal receiving device is reduced, but a considerable concealment effect can be maintained due to the tidal shift effect of the video signal. Furthermore, in addition to the above operations, it is possible to further improve confidentiality by combining operations such as retransmitting the down-synchronization signal. Further, the circuits shown in FIGS. 1 and 2 are only one embodiment of the present invention, and it goes without saying that the present invention is not limited to this circuit. For example, the pulse signal generator of the switching code generation circuit may be Although it was explained that the horizontal synchronization signal frequency is generated by incorporating an independent oscillator, vertical synchronization 1
The No. 8 frequency may be multiplied to generate C. The PN code generated by the PN code generator is configured to be set externally using a key code setting device, but the transmitting side converts the key code into a code and transmits it using the °C vertical retrace interval #. This can also be read and set automatically on the receiving side. Note that the sample and hold circuits 2a and 2b in FIG.
It is clear that if the pedestal level is sampled and held instead of the peak value of the horizontal synchronization signal, the pedestal level can be controlled to the same level. The characteristic is that there is little deterioration of the image even if it is used.

As explained in detail above, the video signal transmission system of the present invention can achieve sufficient confidentiality through a simple operation in which the composite video signal including the horizontal synchronization signal is inverted and transmitted according to the PN code on the transmitting side. This has the effect of restoring a high-quality video signal without being affected by DC drift or low-frequency fluctuation components during restoration processing using reception oil, and strictly matches the inversion reference level between the sending and receiving sides. The advantage is that there is no need to

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the transmitting side video processing section of the present invention, FIG. 2 is a block diagram of an embodiment of the receiving side video processing section of the present invention, and FIGS. b) is a waveform diagram showing an inverted and restored signal waveform; 1.16.17----Differential amplifier, 2 t 2 a
*2 b ・”・・・Sample hold circuit, 3*
3at3b...Composite synchronous separation circuit, 4.4a.
・River・Low pass filter, 5・・Group・Clamp circuit% 6
, 5a...Inversion amplification 4ffl, 7.7a. 10.10'...Non-inverting amplifier s s, sa,
sb...F g T switch, 9... River scramble circuit, 9'... Descramble circuit,
11. lla...Vertical synchronization separation circuit, 12,1
2a... group pulse signal generator, 13° 13a...
...PN code generator, 14, 14a...Key code setter, 15.15' Yamada switching signal generation circuit, 1
8...Feedback circuit. Agent Patent Attorney Uchihara Consumer/Figure No.? Figure 3I￥1 1 (θ2 (b)

Claims (1)

[Claims] In a video signal transmission method in which a television video signal is subjected to waveform conversion processing in a video processing unit on a transmitting side, and restoration processing is performed in a restoration processing unit on a sending and receiving side to reproduce the original signal, the video processing unit on the transmitting side at least Composite video (
The white level of the inverted video signal is transmitted with the polarity reversed, just as the peak value of the horizontal synchronization signal is not inverted, and the restoration processing section on the receiving side inverts the polarity. A video signal transmission system characterized by comprising a clamping means for returning the composite video signal according to the pseudo-random code and inverting and restoring the @l+gorge signal.