JPH02260883A - Scramble system for charged broadcast signal - Google Patents

Abstract

PURPOSE:To attain sufficient scramble even to an audio signal by providing a means stopping a matrix processing of a matrix circuit so as to introduce a demodulation output of a subchannel signal when a specific key data is inputted. CONSTITUTION:The system is provided with means 233-237, 241-246 identifying a mode signal and applying matrix processing to a demodulation output of main and subchannel signals when the signal represents the stereo mode and a means 211 stopping the matrix processing operation of a matrix circuit 250 to introduce the demodulated output of the sub channel signal when a specific key data is inputted regardless of the mode signal representing the stereo mode. Thus, only a subscriber acquiring the specific key data or recognizing it listens to the demodulation output of the subchannel signal as an audio signal and a terminal equipment not acquiring the specific key data cannot listen to the audio signal because noise is subject to matrix processing.

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 descramble 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.

The descramble information indicating the level compression position is the audio F
The AM signal is superimposed on the M signal and transmitted to the subscriber terminal. On the receiving device side, the FM audio signal is subjected to AM detection to extract descramble 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. 6 shows signal waveforms in scrambling processing and descrambling 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 descramble 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 descramble information. The portion subjected to level compression and expansion is usually the horizontal synchronizing signal period.

FIG. 7 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 descramble information from the control circuit 4 is superimposed. The FM audio intermediate frequency superimposed with descramble information is sent to a high frequency modulator 8.
The video signal is input to the video signal generator, and is output as a high frequency signal along with a scrambled video intermediate frequency signal, and 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. 8 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.

(Problems to be Solved by the Invention) Conventional scrambling systems are primarily focused on making images invisible or difficult to view. No measures have been taken to prevent audio from being scrambled.

However, depending on the content of the broadcast, some programs can be enjoyed even by listening to the audio alone, and the significance of making the program a paid program may be lost.

Therefore, an object of the present invention is to provide a scrambling system for pay programs that can perform sufficient scrambling even on the audio signal 1.

[Structure of the Invention] (Means for Solving the Problems) This invention provides a main channel signal and a sub-channel signal having different carrier frequency bands from a transmitting device, and furthermore, the audio signal contents of the main channel and the sub-channel are monaural, stereo , an audio multiplex broadcast signal including a mode signal for identifying whether the audio signal is an independent audio signal, a receiving device receives the audio multiplex broadcast signal, determines the mode signal, and converts the audio signal into a monaural or two-stereo signal. , a system for controlling a decoder in a form adapted to each signal processing of an independent audio signal, wherein the transmitter side includes means for including a mode signal indicating a stereo mode in the audio multiplexed signal as the mode signal; The receiving device side includes means for including an interfering signal in the audio multiplexed signal as a channel signal, and means for including an audio signal to be transmitted as the sub-channel signal in the audio multiplexed signal, and the receiving device side means for demodulating each of the sub-channel signals; means for identifying the mode signal and, if the mode signal is a stereo mode, matrixing the demodulated outputs of the main and sub-channel signals; and the mode signal indicates the stereo mode. However, when specific key data is input, the matrix processing operation of the matrix circuit is stopped.

and means for deriving a demodulated output of the sub-channel signal.

(Function) With the above means, only the subscriber who has acquired or knows the specific key data can hear the demodulated output of the subchannel signal as an audio signal, and the terminal that cannot obtain the specific key data can hear the demodulated output as an audio signal. Since the (interfering signal) is matrix-processed, the audio cannot be heard.

(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. 3 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. 4 shows the configuration of the teletext signal transmitting side.

The main audio signal is supplied to an audio transmitter 420 via an 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 the FM modulator 40B 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, a switch in the matrix circuit section 402 is changed to produce a sum signal (L+R) and a difference signal (L-R), respectively, for the main channel and the difference signal (L-R). Input to the secondary channel side.

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 440.

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
92.5) A 1z pilot signal is supplied, and when stereo broadcasting is performed, a 982.5Hz pilot signal is supplied. The AM modulator 434 modulates the carrier approximately 3.5 times the horizontal synchronization signal frequency with the pilot signal, and transmits the modulated output to the audio transmitter 42.
0.

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 synchronization signal.

FIG. 5 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 50B, and a low-pass filter 507.

On the other hand, a signal indicating the broadcast mode is separated by a bandpass filter 503 and input to an amplifier 523, whose output 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 input 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 982.5Hz
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 514
output is turned on. As a result, the squelch circuit 52B
1 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. 1(A) shows a transmitter, in which an interference signal is supplied to an input terminal 100, and is input to an audio transmitter 106 via a pre-emphasis circuit 102, a limiting amplifier 103, a delay circuit 104, and a low-pass filter 105. Ru.

On the other hand, an audio signal for transmission is supplied to an input terminal 110 and passed through a pre-emphasis circuit II2, a limiting amplifier 113, an instantaneous deviation controller 114, and a low-pass filter 115.
The signal is input to the modulator 11B and frequency modulated. The signal is then supplied to the audio transmitter 10B via the bandpass filter 117.

On the other hand, the video signal is input to the video transmitter 121 via the input terminal 120, converted into a transmission frequency, and sent out to the CATV transmission line via the diplexer 107.

131 is a synchronization separation circuit, and the horizontal synchronization signal separated here is input to an AM modulator 132 and used to create a mode signal. That is, the AM modulator 132 has
A pilot signal (982, 5H2) indicating the stereo mode in the audio multiplex system is supplied from the oscillator 133. The AM modulator 132 uses the pilot signal to perform AM on a carrier approximately 3.5 times the frequency of the horizontal synchronization signal.

Its modulated output is supplied to audio transmitter 10B.

The output of audio transmitter 106 is fed to diplexer 107.

134 is a circuit that creates a carrier used in the FM modulator 11B, and uses a phase locked loop circuit (APC) that is phase-locked to a horizontal synchronization signal.

As described above, when an audio signal and a mode signal are transmitted, the receiving system on the receiving side normally switches to the stereo mode automatically.

In stereo mode, signals are processed in a matrix on the main channel side and the sub channel side. Then, in this embodiment, since an interfering signal is inserted into one side, reproduction of the audio signal cannot be obtained. In other words, it is scrambled.

However, it is necessary to ensure that the audio signal can be reproduced satisfactorily on the terminal of the subscriber who has paid the viewing fee for the pay broadcast program.

Therefore, the scramble control signal generating section 141 is provided to transmit descramble information to a specific subscriber terminal. Descramble information is modulated by FSX modulator 142 and diplexer 107
supplied to

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

A signal from the CATV transmission line is supplied to a tuner 212 and an FSK demodulator 211 via an input terminal 210.

The FSK demodulator 211 is provided, for example, only by a subscriber who has made a contract, or is set so that only the terminal of a subscriber who has made a contract can specifically obtain a reception code.

The video intermediate frequency output from the tuner 212 is guided to the video detection section 213. The video detection output is supplied to a high frequency modulator 241, converted to a frequency that can be received by a television receiver, and output.

In the video detection section 213, an audio intermediate frequency signal (FM signal)
is also derived and supplied to the audio FM detection section 215. The audio FM detection section 215 outputs the main channel signal and the FM
The state sub-channel signal is obtained. The main channel signal (in this system, the interfering signal) is transferred to the de-emphasis circuit 225. It is supplied to matrix circuit 250 via amplifier 226.

The sub-channel signal is extracted by bandpass filter 217 and supplied to amplifier 218 . And the amplified F
The M signal is input to an FM detector 220 via a limiter 219 and demodulated. The demodulated output is amplified by an amplifier 222 via a de-emphasis circuit 221 and input to a matrix circuit 250 .

Further, a control signal including a pilot signal (indicating stereo mode in this case) is separated by a bandpass filter 217 and amplified by an amplifier 231. The output of the amplifier 231 is
The AM detector 232 detects the wave and extracts the pilot signal. The output of the AM detector 232 is sent to the lead filter 233.
(for 922,511z extraction) and lead filter 241
(for 982,5Hz extraction).

The output terminal of the reed filter 233 is connected to an amplifier 234, and the output of the amplifier 234 is configured to be rectified by a rectifier circuit 235 and supplied to the control circuit 23B. Furthermore, the output of the lead filter 241 is sent to the amplifier 242.
The output of this amplifier 242 is amplified by a rectifier circuit 243.
The configuration is such that the signal is rectified by the following and supplied to the control circuit 245. The output of the control circuit 236 is sent to the squelch circuit 237.
The output of the control circuit 245 is supplied to the squelch circuit 23.
7 and matrix switching circuit 248.

Therefore, basically in this system, the matrix circuit 250 is switched to stereo mode.

Therefore, the signal obtained from the matrix circuit 250 is
It becomes noise.

However, in the case of a subscriber who has subscribed to and pays a fee for a pay broadcast program, descramble information can be obtained from the FSK demodulator 211. This descramble information is supplied to matrix circuit 250. Then, even though the stereo mode signal is being received, the matrix circuit 250 extracts only the reproduction output on the sub-channel side and supplies it to the audio multiplex encoder 260.

The audio multiplex encoder 260 includes a matrix circuit 250
This is a circuit that converts the audio signal obtained from the above into a normal audio multiplexing system signal and supplies it to the high frequency modulator 214 as an audio intermediate frequency. Therefore, the television receiver can process it as a normal audio multiplex broadcast signal. In this case, if descramble information is obtained from the FSK demodulator 211, this information is also supplied to the audio multiplex encoder 260. Thereby, the audio multiplex encoder 260 can guide the audio signal obtained from the matrix circuit 250 to the terminal on the side of the sub-channel to the input terminal on the side of the main channel.

In the above explanation, an example has been described in which the audio signal is scrambled, but normal audio multiplex broadcasting may be performed. In this case, no received code appears from the FSK demodulator 211. Although omitted on the transmitting side, in the case of bilingual broadcasting, a 922.5 Hz pilot signal is sent out and transmitted as a control signal. In this way, when normal audio multiplex broadcasting is performed, the matrix circuit 2
50 is controlled by a mode signal, and in the case of a stereo signal, outputs L channel and R channel signals, and also outputs a bypass signal of 982.5Hz or 922.5H.
z identification signal to the audio multiplex encoder. In this case, since there is no descramble information, the main channel and sub channel signals obtained from the matrix circuit 250 are set to be guided to the main channel and sub channel signal input terminals of the audio multiplex encoder 260, respectively. .

In the above embodiment, as shown in FIG. 2(A), the interference signal is transmitted using the frequency band of the main channel, the audio signal to be transmitted is transmitted using the frequency band of the sub-channel, Further, as a control signal, a signal indicating a stereo mode was transmitted.

However, it is not limited to this method, and as shown in Figure 2 (B
) The transmission signal and band may be set as shown in ().

That is, the frequency band of the main channel is used as an interfering signal or no signal, and the frequency band of the sub-channel is used to transmit the audio signal to be transmitted. Then, no control signal is transmitted.

When set in this way, since there is no control signal, the receiving side determines that the mode is monaural mode.

When in mono mode, the signal processing function is switched to reproduce only the main channel signal. Therefore,
In this case as well, the signal output from the matrix circuit becomes noise or no signal and can be scrambled. However, since the subscriber's terminal can receive descramble information for switching the processing mode to the sub-channel processing mode, good audio reproduction output can be obtained from the matrix circuit.

Further, in the present invention, the scrambling mode in the first embodiment and the scrambling mode in the second embodiment described above may be switched over in time.

[Effects of the Invention] As explained above, the present invention can perform sufficient scrambling on audio signals.

[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)
2 is a block diagram showing the receiving device side, FIG. 2(A) is a frequency spectrum diagram shown to explain the system of FIG. 1, and FIG. 2(B) is a diagram showing another embodiment of the present invention. Figure 3 is a frequency spectrum diagram used in the audio multiplex broadcasting system, Figure 4 is a diagram showing the transmitter of the audio multiplex system, and Figure 5 is a diagram showing the receiver of the audio multiplex system. 6 is a signal waveform diagram shown to explain the video scrambling system, and FIG. 7 is a diagram showing the transmitting device of the video scrambling system.
8 is a diagram showing a receiving device of a video scrambling system. 102.112... pre-emphasis circuit, 103,
1131. . Limiting amplifier, 105, 115...Low pass filter, 10
B... Audio transmitter, 107... Diplexer, 11
B... FM modulator, 117... Bandpass filter, 12
1... Video transmitter, 131... Synchronization separation circuit, 13
2...AM modulator, 133...oscillator, 134...
・Phase-locked loop circuit, 212...Tuner, 211
...FSK demodulator, 213...video detection section, 214
... High frequency modulator, 215 ... Audio FM detection section, 2
18.218, 231, 234, 242, 222.22
8...Amplifier, 219...Limiter, 220...
FM detector, 221.225... De-emphasis circuit, 232... AM detector, 233.241... Lead filter, 235.243... Rectifier circuit, 236
, 245...control unit, 250...between and circuit, 260
...Audio multiplex encoder. Applicant's agent Patent attorney Takehiko Suzue Figure 8

Claims (2)

[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 a receiving device receives the audio multiplex broadcast signal, determines the mode signal, and converts the decoder into a form suitable for signal processing of monaural, stereo, and independent audio signals. In the controlling system, the transmitter side includes means for including a mode signal indicating a stereo mode in the audio multiplexed signal as the mode signal, and means for including an interfering signal in the audio multiplexed signal as the main channel signal. , means for including an audio signal to be transmitted as the sub-channel signal in the audio multiplexed signal, and on the receiving device side, means for demodulating the main channel signal and the sub-channel signal, and identifying the mode signal. means for matrixing demodulated outputs of the main and sub-channel signals when the mode is stereo mode; and means for determining whether specific key data is input even though the mode signal indicates stereo mode. Then, the matrix processing operation of the matrix circuit is stopped by
A scrambling method for a pay broadcast signal, comprising means for deriving a demodulated output of the sub-channel signal. (2) 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 a receiving device receives the audio multiplex broadcast signal, determines the mode signal, and converts the decoder into a form suitable for signal processing of monaural, stereo, and independent audio signals. In the control system, the transmitter side includes means for transmitting a signal indicating monaural (no signal) as the mode signal, means for including an interfering signal or no signal as the main channel signal in the audio multiplexed signal, and means for transmitting a signal indicating monaural (no signal) as the main channel signal; means for including an audio signal to be transmitted as a channel signal in the audio multiplexed signal, and on the receiving device side, means for demodulating each of the main channel signal and the sub-channel signal, and identifying the mode signal, means for obtaining a demodulated output of the main channel signal when there is no signal; and means for obtaining a demodulated output of the main channel signal when the mode signal indicates monaural, and a signal of the sub channel signal by inputting specific key data. 1. A method for scrambling a pay broadcast signal, comprising means for performing processing and deriving a demodulated output thereof.