JPH05344501A - Sound scrambling device - Google Patents

Abstract

PURPOSE:To prevent the illegal listening of a sound signal by transmitting a sound-multiplexed signal obtained by superimposing a noise signal to a main signal and arranging a monaural sound signal to a sub-signal together with scrambling information. CONSTITUTION:An input video signal is modulated to a video carrier by a video modulator 29 and a timing pulse corresponding to the position of a synchronizing signal for the video signal is formed by a timing pulse generator 30. The position of the video carrier which corresponds to the synchronizing signal is level-compressed by a variable gain amplifier 31 based upon the timing pulse. On the other hand, the center frequency 2fH output FM modulation of the sound signal is executed by a sound scrambling modulator 33, the modulated signal is added to a sine wave signal of 1kHz and the multiplexed sound signal is converted into an FM signal by an FM modulator 34 as to audio carrier. The video carrier and the audio carrier are mixed with each other by a mixer 36 and the mixed signal is sent together with service information outputted from a microprocessor 40 through a combiner 38. The receiving side detects the main signal and the sub-signal and outputs only the sub-signal based upon scrambling information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter and a receiver for broadcasting a pay program in a CATV (cable television) system or the like, and more particularly to an audio scrambler for scrambling the audio signal. ..

[0002]

2. Description of the Related Art As is well known, in the CATV system, when a pay program is broadcast, a video signal is scrambled at a broadcasting center and sent to a subscriber terminal device. A descrambling circuit is provided in the terminal device of the subscriber who has subscribed to the pay program, and the descrambling process is performed by the circuit according to an instruction from the broadcasting center, so that the original video signal is obtained. Is being reproduced.

FIG. 3A shows a video carrier scrambled by an RF (high frequency) synchronous compression method. The video carrier is scrambled by level-compressing the portion of the video signal corresponding to the horizontal or vertical synchronizing signal. By level-compressing the position corresponding to the sync signal of the video signal in this way, the sync signal is not reproduced even when video detection is performed by a normal method, so that a normal video signal cannot be obtained. And in this RF synchronous compression system,
By changing whether or not the position corresponding to the synchronizing signal of the video signal is level-compressed for each horizontal synchronization, it is possible to further improve the disturbance due to the out-of-synchronization of the television screen.

FIG. 3 (b) shows an audio carrier, which is transmitted by being subjected to AM modulation of a timing pulse synchronized in time with a signal position of a scrambled video carrier. Then, on the receiving side, the audio carrier is AM-demodulated to reproduce a timing pulse, and the level compression position of the scrambled video carrier is inversely expanded (gain control) in synchronization with this pulse. A normal video carrier as shown in (c) can be obtained.

FIG. 4 shows the structure of a subscriber terminal device for receiving and reproducing the above scrambled signal. That is, the scrambled signal supplied to the input terminal 11 is passed through the distributor 12 to the up-down converter 1
Input to 3. This up-down converter 13
The tuning data sent from the microcontroller 14 is given to a PLL (phase locked loop) circuit 15 to select a broadcasting channel corresponding to the tuning data.

That is, the channel selection system using the up / down converter 13 is configured as follows. The output of the voltage-controlled first local oscillator (not shown) built in the up-down converter 13 is supplied to the PLL circuit 15, where it is divided and compared with the output of a reference oscillator (not shown). And the error output by this comparison result is
It is supplied to the control terminal of the first local oscillator through an LPF (low pass filter) 16 and its oscillation frequency is controlled. Therefore, it is possible to select a broadcast channel by changing the frequency division ratio of the output of the first local oscillator in the PLL circuit 15 according to the tuning data output from the microcontroller 14.

The output of the up / down converter 13 is input to the descramble circuit 18 via the distributor 17 and is descrambled. On the other hand, the converted output obtained from the up / down converter 13 is supplied to the audio carrier AM demodulator 19 via the distributor 17. The audio carrier AM demodulator 19 detects a timing pulse indicating the compression position of the video carrier and supplies the timing pulse to the descramble circuit 18 to set the timing for expanding the compression position of the video carrier.

As a result, normal video carriers and audio carriers are obtained from the descrambling circuit 18, and these are supplied to the video / audio detection circuit 20, whereby the video signal is taken out from the output terminal 21 and the output terminal 22. , 23, L (left) and R (right) audio signals are extracted.

Further, various service data are also sent from the broadcasting center to the subscriber terminal device, and one of these signals can use an FSK modulated wave using a frequency around 70 MHz. Many. This FSK modulated wave is introduced into the FSK demodulator 24 via the distributor 12,
It is demodulated here and input to the microcontroller 14. The microcontroller 14 uses the service data to execute processing such as determination of the program code of the current broadcast program and determination of whether the currently selected program is reserved. Then, when the subscriber has reserved the currently selected program, the control signal for starting the operation is given from the microcontroller 14 to the descramble circuit 18. Further, a keyboard 25 for selecting a broadcast channel, a display 26, an oscillator 27, etc. are connected to the microcontroller 14.

By the way, the above-described scramble system has an advantage that a circuit for scramble processing and descrambling processing can be realized economically and advantageously with a simple structure, but a scramble effect for a video signal is expected. However, there is a problem that the scramble effect on the audio signal cannot be expected at all.

That is, there are many CAs currently on the market.
Considering that the television receiver for TV is simply used as a demodulator of an audio signal, the above scramble system is completely unprotected. Depending on the contents of the pay program, there are many programs that are worth listening only to the sound, and it is a serious problem that the scramble effect on the sound signal cannot be expected at all.

[0012]

As described above, in the conventional scramble system, the scramble effect for the video signal can be expected, but the scramble effect for the audio signal cannot be expected, and the unauthorized listening of the audio signal can be prevented. I have a problem that I can not.

Therefore, the present invention has been made in consideration of the above circumstances, and it is possible to prevent unauthorized listening to a voice signal and to realize it economically with a simple structure. An object is to provide a good audio scrambler.

[0014]

SUMMARY OF THE INVENTION A voice scrambler according to the present invention provides a voice multiplex signal in which a main signal is a noise signal and a sub signal is a monaural voice signal. Transmitting means for transmitting together with the scramble information indicating that the pilot signal and the main signal are noise components, and receiving the output of this transmitting means to detect the main signal and the sub signal of the audio multiplex signal respectively, and based on the scramble information And a receiving means for outputting only the sub signal.

[0015]

According to the above-mentioned structure, a voice multiplex signal in which a noise signal is superposed on a main signal and a monaural voice signal is arranged as a sub-signal on a transmitting side is used as a pilot signal having a polarity corresponding to monaural. Since the main signal and the scramble information indicating that the main signal is a noise component are transmitted together, the receiving side detects the main signal and the sub signal of the audio multiplex signal and outputs only the sub signal based on the scramble information. ,
In the scrambled audio signal, the pilot signal has a monaural polarity even if it is received by a normal television receiver, so it is not processed as audio multiplex broadcasting and only the main signal (noise) is output, and normal audio is output. Since the signal cannot be obtained and the sub signal (audio signal) can be output only by the receiving means having the descrambling function, it is possible to prevent unauthorized listening to the audio signal, and it is simple. With such a structure, it can be realized economically advantageously.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a system on the transmitting side, and reference numeral 28 is an input terminal to which a video signal is supplied. The video signal supplied to the input terminal 28 is input to the video modulator 29 and modulated into a video carrier, and is also input to the timing pulse generator 30 to generate a timing pulse corresponding to the position of the synchronizing signal of the video signal. Used for generation. The video carrier output from the video modulator 29 is input to the variable gain amplifier 31. The variable gain amplifier 31 normally outputs the input signal as it is, but when performing scrambling, the position corresponding to the sync signal of the video carrier is determined based on the timing pulse output from the timing pulse generator 30. Output after level compression.

On the other hand, in FIG. 1, reference numeral 32 is an input terminal to which a monaural audio signal is supplied. The audio signal supplied to the input terminal 32 is input to the audio scramble modulator 33, FM-modulated at the center frequency 2f _H (f _H ; horizontal synchronizing frequency), and further added with the 1 kHz sine wave signal. The audio signal thus multiplexed is F
The M modulator 34 converts it into an FM signal and outputs it as an audio carrier. This audio carrier is input to the variable gain amplifier 35. This variable gain amplifier 35
Normally outputs the input signal as it is, but when scrambling is performed, the audio carrier is AM-modulated based on the timing pulse output from the timing pulse generator 30 and output.

The scrambled video carrier output from the variable gain amplifier 31 and the AM-modulated audio carrier output from the variable gain amplifier 35 are mixed by a mixer 36 to form a composite video carrier. The signal is sent from the output terminal 39 to the CATV broadcast network (not shown) via the up converter 37 and the combiner 38.

The transmitting side is also provided with means for transmitting service data to each subscriber terminal device. That is, the service information is output from the microprocessor 40 as serial data, and this serial data is F
After the frequency shift keying modulation is carried out by the SK modulator 41, it is sent from the output terminal 39 to the CATV broadcasting network through the combiner 38.

The transmission side system as described above has a scramble function by the above-mentioned RF synchronous compression system and a scramble function by the voice multiplex system effective for preventing unauthorized listening of a voice signal.

Next, FIG. 2 shows a system on the receiving side. Reference numeral 42 is an input terminal to which a plurality of composite video carriers divided into respective frequencies and service data are supplied. Of these, the composite video carrier is the distributor 43.
Is input to the up / down converter 44 via. The up / down converter 44 selects the broadcast channel corresponding to the tuning data by supplying the tuning data sent from the microcontroller 45 to the PLL circuit 46.

That is, the output of the voltage-controlled first local oscillator 44b of the first frequency converter 44a incorporated in the up-down converter 44 is supplied to the PLL circuit 46,
Here, the frequency is divided and compared with the output of a reference oscillator (not shown). The error output resulting from this comparison is the LPF
It is supplied to the control terminal of the first local oscillator 44b via 47, and its oscillation frequency is controlled. Therefore, the tuning data output from the microcontroller 45 causes P
The broadcast channel is selected by changing the frequency division ratio of the output of the first local oscillator 44b in the LL circuit 46.

Then, the composite video carrier obtained by the up / down converter 44 is input to the variable gain amplifier 49 and the high frequency amplifier circuit 50 via the distributor 48, respectively. Of these, the composite video carrier amplified by the high frequency amplifier circuit 50 is extracted as an audio carrier by a BPF (band pass filter) 51. And
The audio carrier extracted by the BPF 51 is input to the AM detector 52, and when the timing pulse indicating the synchronization position of the video signal is overlapped, the timing pulse is separated. Then, the timing pulse output from the AM detector 52 is waveform-shaped by the timing pulse generator 53 and input to the variable gain amplifier 49.

The variable gain amplifier 49 normally outputs the input signal as it is, but when descramble processing is performed, the synchronizing signal of the composite video carrier is generated based on the timing pulse output from the timing pulse generator 53. The level is extended at the position corresponding to. As a result, a normal video carrier is obtained from the variable gain amplifier 49, and this is supplied to the video detection circuit 54, so that a video signal is taken out from the output terminal 55. Also,
The service data supplied to the input terminal 42 is demodulated by the FSK demodulator 56 and then fetched by the microcontroller 45.

On the other hand, the audio carrier output from the BPF 51 is supplied to the FM detector 57 and FM-detected to become an MPX (multiplex) signal, and the FM detector 58, the pilot detector 59, and the de-emphasis. By being supplied to the matrix switching circuit 60, the L and R audio signals are taken out from the output terminals 61 and 62.

Here, when scrambling is performed on the transmitting side, the sub-signal is carried in the absence of a pilot signal of the voice multiplex signal, and a sine wave of 1 kHz is sent as noise to the main signal. When demodulating the audio signal processed in this way, the microcontroller 45 controls the de-emphasis matrix switching circuit 60 regardless of the polarity detected by the pilot detector 59, and outputs it from the FM detector 58. The sub-signal of the output terminals 61, 62
Output to. In the normal mode, the de-emphasis / de-emphasis is performed according to the polarity detected by the pilot detector 59.
The matrix switching circuit 60 is connected to the microcontroller 45.
Is controlled to output the audio signal to the output terminals 61 and 62.

This switching information is transmitted to the microcontroller 45 via the previous FSK modulation / demodulation path, and only the subscriber who has the contract can reproduce the voice information.

Therefore, according to the configuration of the above-described embodiment, in the case of monaural broadcasting, the transmitting side arranges the main signal of the audio multiplexed signal with noise and the sub-signal with the original audio signal, and the pilot signal. Since the polarity of is transmitted as monaural and the receiving side detects the main signal and the sub-signal of the audio multiplex signal and outputs only the sub-signal, the scrambled audio signal can be output as a normal television signal. Even if it is received by the receiver, the pilot signal has a monaural polarity, so that it is not processed as a voice multiplex broadcast and only the main signal (noise) is output and a normal voice signal cannot be obtained. On the other hand, the receiving side having the descrambling function can output the sub signal (original audio signal), so that a normal audio signal can be obtained. The present invention is not limited to the above embodiment,
In addition, various modifications can be made without departing from the scope of the invention.

[0029]

As described in detail above, according to the present invention,
It is possible to provide an extremely good audio scramble device which can prevent unauthorized listening to an audio signal and can be economically realized with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a structure of a transmitting side, showing an embodiment of a voice scrambling device according to the present invention.

FIG. 2 is a block configuration diagram showing a structure of a receiving side of the embodiment.

FIG. 3 is a diagram for explaining scrambling processing by an RF synchronous compression method.

FIG. 4 is a block diagram showing the structure of a conventional subscriber terminal device.

[Explanation of symbols]

11 ... Input terminal, 12 ... Distributor, 13 ... Up-down converter, 14 ... Micro controller, 15 ... PLL
Circuit, 16 ... LPF, 17 ... distributor, 18 ... descramble circuit, 19 ... audio carrier AM demodulator, 2
0 ... Video / audio detection circuit, 21-23 ... Output terminal, 24 ...
FSK demodulator, 25 ... Keyboard, 26 ... Display, 27 ... Oscillator, 28 ... Input terminal, 29 ... Video modulator, 30 ... Timing pulse generator, 31 ... Variable gain amplifier, 32 ... Input terminal, 33 ... Audio scramble modulation Unit, 34 ... FM modulator, 35 ... Variable gain amplifier, 36 ...
Mixer, 37 ... Up-converter, 38 ... Combiner, 39 ... Output terminal, 40 ... Microprocessor, 41
... FSK modulator, 42 ... Input terminal, 43 ... Distributor, 44
... Up-down converter, 45 ... Micro controller, 46 ... PLL circuit, 47 ... LPF, 48 ... Distributor,
49 ... Variable gain amplifier, 50 ... High frequency amplifier circuit, 51 ...
BPF, 52 ... AM detector, 53 ... Timing pulse generator, 54 ... Video detection circuit, 55 ... Output terminal, 56 ... F
SK demodulator, 57 ... FM detector, 58 ... FM detector, 5
9 ... Pilot detector, 60 ... De-emphasis matrix switching circuit, 61, 62 ... Output terminals.

Claims (1)

[Claims] 1. A voice multiplex signal comprising a main signal and a noise signal superimposed on each other and a monaural voice signal arranged on a sub-signal, wherein a pilot signal having a polarity corresponding to monaural and the main signal are noise components. Transmitting means for transmitting together with the scramble information shown, and receiving means for receiving the output of the transmitting means, detecting the main signal and the sub signal of the voice multiplexed signal respectively, and outputting only the sub signal based on the scramble information. An audio scrambler comprising: