JPH02260885A - Scramble system for charged broadcast signal - Google Patents

Abstract

PURPOSE:To apply efficient scramble to both an audio signal and a video signal without descramble information giving adverse effect onto other signals by providing a specific descramble information transmission means and an extraction means. CONSTITUTION:A sender equipment side is provided with a means setting the presence of transmission of a mode signal or a frequency to identify the transmission of descramble information through the use of a main channel. A receiver equipment side is provided with a means to discriminate the setting, a means releasing the scramble of a reception video signal, and a means stopping forcibly the operation of the release means. That is, a signal from a CATV transmission line is fed to an UP-DOWN converter and a tuner section 201 via an input terminal 200 and a video intermediate frequency obtained from them is fed to a gain changeover circuit 202 and descrambled. A synchronizing expansion signal for descramble is given from a switch S11. Thus, adverse effect of descramble information onto other signals is prevented and the scrambling of the audio signal is obtained as soon as that of the video signal is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) This invention is applicable to cable television (hereinafter referred to as CAT
The present invention relates to a scrambling method for pay broadcast signals used in broadcasting (denoted as V).

(Prior Art) In a CATV system, video signals of pay broadcast programs are scrambled and transmitted so that only subscribers who have descrambling information for unscrambling can view the video signals. . There are various scrambling methods, and among them, the synchronous compression method is one that can be realized relatively easily. This method is a method in which the positions of synchronization signals (horizontal and vertical synchronization signals) are level-compressed and transmitted with respect to the video intermediate frequency to be broadcast. Descrambling information indicating the level compression position is superimposed on the audio FM signal in the form of AM and transmitted to the subscriber terminal. On the receiving device side, the FM audio signal is subjected to AM detection to extract descrambling information, and based on this information, the position where the level has been compressed is determined, and an expanded pulse is created. Then, the level of the video intermediate frequency is controlled at the timing of the expansion pulse to obtain a normal intermediate frequency (unscrambled signal).

FIG. 7 shows signal waveforms in scramble processing and descramble processing. The figure (a) shows the video intermediate frequency on the transmitting side, the figure (b) shows the video intermediate frequency subjected to synchronous compression, and the figure (c) shows the FM audio intermediate frequency on which information for descrambling is superimposed. , is superimposed in the form of a square wave at the same time position as the synchronous compression position. The same figure (d
) is the descrambling information extracted from the audio intermediate frequency, and (d) in the figure is the video intermediate frequency whose level-compressed portion has been expanded based on the descrambling information. The portion subjected to level compression and expansion is usually the horizontal synchronizing signal period.

FIG. 8 shows an encoder provided on the transmitting side to perform scrambling.

The video signal is supplied via an input terminal 1 to an intermediate frequency modulator 2 and a scramble control circuit (hereinafter referred to as control circuit) 4. The video intermediate frequency is level-compressed in the synchronization period in the gain switching circuit 3 based on the compression signal from the control circuit 4, and is supplied to the high frequency modulator 8.

On the other hand, the audio signal is supplied to the audio intermediate frequency modulator 6 via the input terminal 5, becomes an FM audio intermediate frequency, and is input to the gain switching circuit 7, where the descrambling information from the control circuit 4 is superimposed. The FM audio intermediate frequency on which descramble information has been superimposed is sent to a high frequency modulator 8.
The signal is then input manually and output as a high-frequency signal together with a scrambled video intermediate frequency signal, which is then sent to a cable.

The control circuit 4 separates vertical and horizontal synchronizing signals from the video signal and synchronizes them with these signals to determine the output timing of the level compression signal.

FIG. 9 shows a decoder on the receiving side.

The received signal is sent to the up/down tuner 1 via the terminal 11.
2 and converted to an intermediate frequency.

The video intermediate frequency is supplied to a gain switching circuit 13, and the FM audio intermediate frequency is supplied to an AM detector 14.

The AM detector 14 extracts the control signal and outputs the control signal to the waveform shaping circuit 1.
5 to the timing adjustment circuit 16. The timing adjustment circuit 16 generates an expanded signal based on the descramble information and supplies it to the gain switching circuit 15. As a result, a descrambled video intermediate frequency is obtained from the gain switching circuit 15 and supplied to the television receiver via the output terminal 17.

(Problem to be solved by the invention) ■ Conventionally, descramble information was converted into audio intermediate frequency by AM.
It is transmitted in a superimposed manner. For this reason, if the audio intermediate frequency is extracted and the signal shape, pattern, timing, etc. of the descrambled information is analyzed using a synchroscope or the like, there is a possibility that the audio can be viewed and viewed in secret.

- In conventional systems, a square wave or a double sine wave obtained by smoothing the square wave is used as a signal to form descramble information. For this reason, with respect to the normal video signal spectrum as shown by the solid line in Figure 10, AM modulation of the FM audio signal causes the audio spectrum to change in the high range of the video signal, especially in the color signal region, as shown by the dotted line. There are interferences to the video signal, such as the occurrence of color beats and an increase in color noise. Furthermore, if a situation occurs where AM impulse noise is mixed into the transmission path, there is a possibility that the noise will be mistakenly determined to be a control signal, resulting in a malfunction in the descrambling operation.

(2) Also, a control signal in the form of AM may remain on the audio intermediate frequency. This residual component is the synchronizing signal frequency component of the video signal (vertical frequency 80H2% horizontal frequency 15.7
34KH2). Then, if the AM component removal ability of the audio detection circuit is insufficient, the residual component is detected as audio and output as noise.

■Furthermore, conventional systems only take measures against scrambling of video signals, but depending on the content of the program,
There are things that can be enjoyed just by listening to the audio, and the value of paid programs may be diminished.

(2) In addition, conventional scrambling methods do not have a countermeasure that combines the video signal and the audio signal, and scrambling of each signal is considered independently, which requires separate and expensive equipment.

Therefore, the present invention employs a method for superimposing and extracting descramble information that is different from the conventional method, thereby eliminating the adverse effect of descrambling information on other signals, and efficiently scrambling both audio and video signals. To provide a pay program scrambling system that can realize the same function at a low cost.

[Structure of the Invention] (Means for Solving the Problems) This invention effectively utilizes an audio multiplex broadcast signal processing system and uses the signal area of the main channel as a descrambling information area for a video signal. At the same time, descramble information transmission means and extraction means are provided so that this information can function as a scramble signal for an audio signal.

(Function) By the above means, the audio intermediate frequency itself is
There is no need to do this, and the problems that have arisen due to this AM are eliminated. Furthermore, since the descrambling information of the video signal is transmitted on the main channel, the audio signal must also be scrambled on the receiving side.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, with (A) showing the transmitting device side and FIG. 1(B) showing the receiving device side.

This system effectively utilizes an audio multiplex broadcast system, and first, the audio multiplex broadcast system will be explained.

There are established main standards for audio multiplex broadcasting systems.

FIG. 4 shows the frequency spectrum of the audio multiplex broadcast signal. The signal band in conventional monaural broadcasting is
Corresponds to the main channel signal part in the figure.

FIG. 5 shows the configuration of the transmission side of the audio multiplex broadcast signal. The main audio signal is supplied to an audio transmitter 420 via a human input terminal 410, a pre-emphasis circuit 411, a matrix circuit section 402, a limiting amplifier 412, a delay circuit 413, and a low-pass filter 414.

The sub-audio signal is sent to a pre-emphasis circuit 401. through an input terminal 400. Matrix circuit section 402, limiting amplifier 4
03, IDC (Instantaneous Deviation Controller) 404, and is input to an FM modulator 406 via a low pass filter (LPF) 405, where it is frequency modulated. The signal is then supplied to an audio transmitter 420 via a bandpass filter 407.

When the signals supplied to the input terminals 400 and 410 are stereo signals, the switch of the matrix circuit section 402 is changed, and a sum signal (LSI?) and a difference signal (LR) are output.
are created and input to the main channel and sub channel respectively.

On the other hand, the video signal is input to the video transmitter 431 via the input terminal 430, converted into a transmission frequency signal, and supplied to the antenna via the diplexer 44G.

The diplexer 440 is also supplied with a transmission frequency signal from the audio transmitter 420.

433 is a synchronization separation circuit, and the horizontal synchronization signal separated here is input to an AM modulator 434 and used to create a mode signal. That is, when bilingual broadcasting is performed, the AM modulator 434 receives 9
A 92.5 Hz pilot signal is supplied, and when stereo broadcasting is performed, a 982.5 Hz pilot signal is supplied. Then, the AM modulator 434 performs AM on a carrier approximately 3.5 times the horizontal synchronization signal frequency using the pilot signal, and transmits the modulated output to the audio transmitter 420.
is supplied to.

Therefore, on the receiving side, the receiving mode can be switched by determining which pilot signal is being transmitted.

435 is a circuit that creates a carrier used in the FM modulator 40B, and uses a phase locked loop circuit (APC) that is phase-locked to a horizontal synchronizing signal.

FIG. 6 shows the receiving side of the audio multiplex broadcast signal.

The audio multiplexed signal input to the input terminal 500 is sent to the amplifier 50.
It is amplified by 1. The main channel signal output from the amplifier 501 is supplied to the amplifier 504, passes through the matrix circuit 505, is further amplified by the amplifier 515, and is then led to the output terminal 517 via the low-pass filter 51B.

On the other hand, the sub-channel signal is extracted by a bandpass filter 503, amplified by an amplifier 511, and then passed through a limiter 512.
The signal is input to the FM detection section 513 via the FM detection section 513.

The output signal detected here is amplified by an amplifier 514 and output to an output terminal 508 via a matrix circuit 505, an amplifier 506, and a low-pass filter 507.

On the other hand, the signal indicating the broadcast mode is separated by the bandpass filter 503 and input to the amplifier 523, and the output thereof is subjected to AM detection. If this detection output is 922.5 Hz (bilingual broadcast), it is extracted by the lead filter 522 and amplified by the amplifier 523. The amplified signal is rectified by a rectifier circuit 524 and inputted to a control circuit 525 . The control output obtained by the control circuit 525 is transmitted to the squelch circuit 52.
6. In addition, the detection output is 982.511z
In the case of (stereo broadcast), the signal is extracted by a read filter 531 and amplified by an amplifier 532. The amplified signal is rectified by a rectifier circuit 534 and input to a control circuit 534. The control output obtained by control circuit 534 is supplied to matrix switching circuit 535. Amplifier 51
Output 4 is turned on. As a result, the squelch circuit 52
6. The matrix switching circuit 535 automatically operates and the processing mode of the system is switched.

The audio multiplex broadcast system is configured as described above, and its mode switching is automated.

The explanation will be returned to the embodiment shown in FIG.

FIG. 1A shows a transmitting device, in which a video signal is supplied to an input terminal 100, and is supplied to a video intermediate frequency modulator 102 where it is converted into a video intermediate frequency. The converted video intermediate frequency is scrambled in the gain switching circuit 103 by level-compressing the synchronizing signal portion. The synchronous compression signal is given from the scramble control circuit 107. The scrambled video intermediate frequency is combined with the audio intermediate frequency in a synthesis circuit 104, input to a high frequency modulator 105, and sent out as a transmission signal to a CATV transmission line.

The video signal at the input terminal 100 is also input to the synchronization separation circuit 106 . The horizontal synchronization signal H1 and the vertical synchronization signal V separated by the synchronization separation circuit 10B are sent to the scramble control circuit 10.
7 and used as a timing reference signal.

The scramble control circuit 107 determines the timing when outputting a synchronous compressed signal, and this determination information becomes descramble information. In other words, if this descramble information is reproduced on the receiving side, the timing of synchronous compression can be detected.

The above descramble information is supplied to one terminal α of the switch S2. Switch S2 and Switch S
3 is a switch for selecting signals to be input to the main channel and sub-channel of the audio multiplex encoder 113. The other input terminal β of the switch S2 is an input terminal tt for the main channel audio signal (L channel in the case of stereo).
i is connected, and this terminal 10 is also connected to one input terminal α of the switch S8. The other input terminal of this switch S3 is connected to an input terminal 112 for a sub-channel audio signal (R channel in the case of stereo).

As described above, the audio multiplex encoder 113 performs signal processing on the subchannel and main channel, and converts the human signal into a frequency band format as shown in FIG.

The output of the switch S2 is supplied to the pre-emphasis circuit 131, and the output of the switch S3 is supplied to the pre-emphasis circuit 1.
32. Pre-emphasis circuit 311, 1
The output of 32 is input to the matrix circuit section 133. In the stereo mode, the matrix circuit 133 creates a sum signal and a difference signal. The sum signal or main channel side signal is passed through the limiter 134 and the low-pass filter 13B.
The signal is input to the adder 154 via the adder 154. The difference signal or the sub-channel side signal is passed through a limiter 135 and a low-pass filter 13.
7 to the FM modulator 138. The FM signal on the sub-channel side modulated here is passed through the bandpass filter 13
9, is supplied to the adder 154 via the frequency shift control circuit 140. Either one of the outputs of the oscillators 150 and 151 is selected by the switch 152 and output to the AM modulator 15.
3 is input. A mode signal (stereo mode, bilingual mode, monaural mode) is output from the AM modulator 153.
is output and supplied to adder 154 via switch S6.

The output of adder 154 is supplied to synthesis circuit 114.

In the combining circuit 114, the outputs of the oscillator tte can further be combined via switches S4 and S5. The frequency of this signal is 3.51'H, and it is transmitted to the subscriber's terminal without scrambling.

FIG. 2 shows signal waveforms at each part of the circuit described above.

3(a) is a video signal, and FIG. 2(b) is a synchronous compressed signal. FIG. 4(c) shows a video intermediate frequency in which the synchronization signal position has been compressed and scrambled. Same figure (
d) is descramble information, and in this example,
The zero crossing point is arranged to correspond to the synchronous compression position.

FIG. 5(e) shows a sub-channel audio signal, and FIG. 1(f) shows an audio multiplexed signal obtained by FM modulating the sub-channel signal and adding it to the main channel. Further, (g) in the same figure shows a waveform obtained by converting the signal in (f) of the same figure into an audio intermediate frequency.

In this way, the audio intermediate frequency is no longer AMed for descrambling information.

FIG. 1(B) shows the configuration of the receiving device.

A signal from the CATV transmission line is supplied to an up/down converter and tuner section 201 via an input terminal 200. The video intermediate frequency obtained from this is supplied to the gain switching circuit 202 and descrambled. A synchronous expansion signal for descrambling is created by a descramble control circuit 208, and is applied via an amplifier 209, a waveform shaping circuit 2IO, and a switch Sll. The video intermediate frequency whose synchronization position has been expanded and scrambled is released is video detected by a video detection circuit 203, and then supplied to a high frequency modulator 204 for converting it again into a receiving frequency for a television receiver. is supplied to the receiver.

The intermediate frequency derived from the tuner section 201 is an audio FM
The signal is supplied to the detector 20B. This results in an audio multiplex signal, which is supplied via an amplifier 207 to an audio multiplex decoder 208 and a bandpass filter 213.

The audio multiplex decoder 208 outputs a reproduction signal on the main channel side and a reproduction signal on the sub-channel side in accordance with the mode signal, as described above.

Among the output signals of the amplifier 207, the main channel side signal is supplied to the matrix circuit section 233 via a de-emphasis circuit 231 and an amplifier 232.

Since the reproduced signal on the main channel side is descrambled information in the scramble mode, this signal is supplied to the amplifier 209 through the matrix circuit section 233. As a result, a descrambled video intermediate frequency can be obtained from the gain switching circuit 2012.

The output of amplifier 207 is further fed to bandpass filter 235 . The FM signal of the subchannel separated here is
FM detector 23 via amplifier 23B and limiter 237
8 will be man-powered. The FM demodulated audio signal is input to the matrix circuit section 233 via a de-emphasis circuit 239 and an amplifier 240. This audio signal is output via the matrix circuit 233 to the input terminal side of the switch S13 and the input terminal β side of the switch S12. The output terminals of the switches S12 and S13 are connected to the main channel side input terminal and the sub channel side input terminal of the audio multiplex encoder 211. This audio multiplex encoder 211
is a part that creates an audio multiplex signal for the audio multiplex decoder provided on the television receiver side, and its output is supplied to the high frequency modulator 204.

In the scramble mode, since descramble information is being transmitted on the main channel side, the switch S12 selects the signal on the terminal β side, and the switch 13 is turned off. Therefore, the audio multiplex encoder 211 operates in monaural mode.

The route for obtaining the control signal for the matrix circuit 233 will be explained.

Bandpass filter 235 separates the 3.51'H signal component and supplies it to AM detector 252 through amplifier 251. This results in 922.511z or 9B2,511
The z components are taken out and extracted by read filters 253 and 254, respectively. In the normal transmission mode, that is, when no scrambling is applied, and in the bilingual broadcasting mode, the output is obtained from the lead filter 253, and is passed through the amplifier 255 and the rectifier circuit 25B to the matrix control unit 25B.
59. Further, in the stereo mode, an output is obtained from the read filter 254 and supplied to the matrix control section 259 via the amplifier 257 and the rectifier circuit 258.

However, in scramble mode, the mode signal is
It's not being transmitted. Then, the matrix control section 259
determines that the mode is normally monaural, and switches the matrix circuit section 233 to monaural processing mode.

However, in the case of subscriber terminals that have a contract, no output is obtained from the bandpass filter 213, so the scramble moto determination circuit 214 detects this. Then, the switch Sll is turned on, the switch S12 is turned to the input terminal β side, the switch S13 is turned off, and the switch S14 is turned off, and the descramble mode processing state is set.

The switch S14 is for inputting a mode signal to the audio multiplex encoder 211 when the video signal is not scrambled.

FIG. 2(h) to FIG. 2(m) are signal waveforms shown to explain the process of descrambling. (h) in the figure is the descramble information output from the de-emphasis circuit 231, and (i) in the figure is a signal obtained by shaping the waveform of this information.

By using this signal, the zero-crossing point of the descramble information can be detected, so based on that detection signal,
A synchronous expansion signal can be obtained as shown in j). (k) in the same figure is a video intermediate frequency signal that has been descrambled, and (1) in the same figure is a reproduced video signal. Also the same figure (m)
is an FM demodulated audio signal on the sub-channel side.

In the above-described embodiment, as shown in FIG. 3A, descramble information is inserted into the frequency domain of the subchannel and transmitted, and no mode signal is transmitted.

However, a stereo mode signal may be transmitted as the mode signal. In this case, on the receiving device side, if a stereo mode signal is determined, the audio multiplex decoder 112 is forcibly switched to a monaural mode processing state and descrambling information is extracted. Figure 3 (B
) is the frequency spectrum of the audio multiplex signal reassembled in the audio multiplex encoder 211.

In this embodiment, it is possible to obtain a scrambled video signal, and at the same time, in a terminal that does not have a descrambling function, a scrambled audio signal can also be obtained. In other words, if the audio multiplex decoder 113 is not forcibly switched to the monaural mode processing state, the decoder automatically switches to the monaural processing mode or the stereo processing mode, so when looking at the main signal or the difference signal, the noise is not in the signal. becomes.

Furthermore, when a television receiver without an audio multiplex decoder processes an audio multiplex signal, a normal television audio processing circuit can demodulate only the 0 to 15 KHz portion, resulting in noise in scramble mode. Furthermore, according to this descramble information transmission method, since it is FM modulated, it cannot be determined by simple observation using a synchroscope or the like, and it is difficult to determine even if a spectrum analyzer is used, thereby improving performance in preventing eavesdropping.

Furthermore, since the descramble information is transmitted using the FM method, it is resistant to transmission line impulse noise.

Further, since AM is not applied to the audio intermediate frequency, there is no adverse effect on the video signal.

In the above embodiment, the descramble information is a signal whose zero crossing point serves as a reference for knowing the synchronous compression position. However, the descramble information is not limited to this format, and can be realized in various formats. For example, it may be transmitted as digital data including synchronization bits.

Furthermore, if the quality of the audio is not so much of an issue, it is possible to add a circuit to the above system that modulates the audio intermediate frequency in the form of AM and transmits descrambling information as in the past. Even if you transmit this information as false information, you can get it.

[Effects of the Invention] As explained above, the present invention uses a method different from the conventional methods for superimposing and extracting descramble information, thereby eliminating the adverse influence of descramble information on other signals, and further reducing the amount of the means. This can be achieved at a reasonable price.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention,
The same figure (A) is a block diagram showing the transmitter side, the same figure (B)
□ is a block diagram showing the receiving device side, Fig. 2 is a signal waveform diagram of each part shown to explain the operation of the device in Fig. 1, and Fig. 3 is a block diagram showing the receiving device side.
Figure (A) is a frequency spectrum diagram shown to explain the system of Figure 1, Figure 3 (B) is a diagram showing the frequency spectrum of the output of the audio multiplex decoder of Figure 1 (B),
Figure 4 is a frequency spectrum diagram used in the audio multiplex broadcasting system, Figure 5 is a diagram showing the transmitting device of the audio multiplexing system, Figure 6 is a diagram showing the receiving device of the audio multiplexing system, and Figure 7 is a diagram showing the audio multiplexing system receiving device. Signal waveform diagrams shown to explain the scrambling method, FIG. 8 is a diagram showing a transmitting device of a video scrambling system, FIG. 9 is a diagram showing a receiving device of a video scrambling system, and FIG. 10 is a diagram showing a conventional scrambling system. It is a frequency spectrum diagram shown to explain a problem. 102... Video intermediate frequency modulator, 103... Gain switching circuit, 104... Synthesizing circuit, 105... High frequency modulator, 10B... Synchronization separation circuit, 107... Scramble control circuit, tta ...Audio multiplex decoder, 1
14... Synthesis circuit, 115... Audio intermediate frequency modulator, 201... Up/down converter, 202...
Gain switching circuit, 203... Video detection circuit, 204...
...High frequency modulator, 20B...Audio FM detector, 20
8... Audio multiplex decoder, 21G... Waveform shaping circuit, 213... Bandpass filter, 214... Scramble mode determination circuit.

Claims (3)

[Claims] (1) To identify main channel signals and sub-channel signals with different carrier frequency bands from the transmitting device, and whether the audio signal contents of the main channel and sub-channel are monaural, stereo, or independent audio signals. An audio multiplex broadcast signal including a mode signal is transmitted, and the video signal is scrambled and transmitted, and descrambling information used for descrambling is transmitted, and the receiving device transmits the audio multiplex broadcast signal. In a system that receives a video signal, determines the mode signal, controls a decoder in a form suitable for signal processing of monaural, stereo, and independent audio signals, and descrambles the received video signal using descrambling information, On the transmitting device side, means for transmitting the descramble information using the main channel, and means for setting whether or not the mode signal is transmitted or a frequency in order to identify that the descramble information is being transmitted. and on the receiving device side, means for determining that the descrambled information is being transmitted on the main channel by determining the presence or absence of the mode signal or the frequency thereof, and a means for determining that the descrambled information is being transmitted on the main channel, and a means for determining that the descrambled information is being transmitted on the main channel, and a means for determining whether the descrambled information is being transmitted on the main channel by determining the presence or absence of the mode signal or the frequency thereof, and according to the determination result of the determining means. irrespective of the content of the mode signal, the signal processing mode of the decoder is forcibly switched to the signal processing mode of only the main channel through which audio is transmitted, and descrambling information is extracted from the signal of the other channel and used. , means for descrambling the received video signal, and means for forcibly stopping the operation of this means to cause the receiving device to perform normal operation when unscrambled audio and video signals are received. A scrambling method for pay broadcast signals, which is characterized by: (2) The transmitting device is configured to transmit the descramble information through the main channel and not transmit the mode signal, and the receiving device transmits only the sub-channel signal when there is no mode signal. 2. The method for scrambling a pay broadcast signal according to claim 1, wherein the scrambling method is configured to perform audio reproduction processing and extract the descrambling information from a signal of a main channel. (3) The transmitting device side is configured to transmit the descramble information through the main channel, and transmit a stereo mode signal as the mode signal, and the receiving device detects the stereo mode signal. 2. The method for scrambling a pay broadcasting signal according to claim 1, wherein the scrambling method for a pay broadcast signal is configured to perform audio reproduction processing on only the signal of the sub-channel and extract the descrambling information from the signal of the main channel.