JP2856270B2 - Television signal scrambling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new scramble system for television broadcast signals mainly in CATV and a method for receiving a signal by the system.

[0002]

2. Description of the Related Art For example, the current scrambling system of broadcast signals in CATV is roughly classified into an RF system and a baseband system. The main methods belonging to the former RF method include a sine wave superimposition method, a video inversion method,
There are synchronous signal compression method, non-linear filter method, etc., and the main methods belonging to the latter baseband method include video inversion and synchronous compression method, video jitter method, time axis inversion method, scan line transition method, and intra-scan line method. There are a signal switching method and a MAC method. In recent years, the number of scrambled broadcast programs has been increasing in Japan along with the spread of CATV, but since the above-mentioned methods have advantages and disadvantages, the methods adopted by CATV stations are different.

[0003]

SUMMARY OF THE INVENTION The present invention mainly comprises a CAT
It is an object of the present invention to provide a television signal scrambling method as a new and simple method different from the above-described conventional scrambling method for V and a signal receiving method based on the method.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a television signal which transmits an amplitude-modulated video signal, a frequency-modulated audio signal, and a downstream signal of a predetermined modulation relating to transmission of required data. A pseudo-sync signal having an amplitude and a predetermined pulse width is generated, and the pseudo-sync signal is provided at a back porch position of a horizontal retrace period of the video signal for a predetermined number of horizontal lines every predetermined number of horizontal lines with a polarity opposite to that of the horizontal synchronization signal. Means for superimposing on the video signal, and means for inverting the phase of the video signal only during the period of superimposing the pseudo-synchronous signal, to provide a scrambled video signal scrambled by the A timing signal superimposed audio signal obtained by amplitude-modulating and superimposing the generated timing signal on the audio signal, and the scrambled video signal. A scrambling method of a television signal that transmits the downlink signal including the indicated data, and a reception of a television transmission signal by the scrambling method, a video intermediate frequency signal obtained by frequency-converting a received RF signal. A descrambling unit for performing scramble decoding of the scrambled video signal obtained by demodulation; a timing signal detecting unit for AM-detecting an audio intermediate frequency signal obtained by frequency-converting the RF signal to detect the timing signal; An amplification unit that amplifies the timing signal detected by the detection unit; a scramble decoding signal generation unit having a pulse width that matches the phase inversion period of the video signal based on the timing signal amplified by the amplification unit; and When a signal is input and turned on, the descramble section A switching circuit for transmitting a signal for descrambling and stopping transmission of the signal for descrambling when the signal is off, and turning on the switching circuit from specific data included in demodulated data of the downlink signal obtained from the RF signal. Or a control unit for performing off switching control, and a method for receiving a transmission signal based on the scrambling method, wherein the descrambling unit performs scramble decoding of a scrambled video signal only when the switching circuit is turned on. Is provided.

[0005]

(1) Transmitting side In the so-called back porch portion of a horizontal retrace period of the original video signal from a VTR, a camera or the like, a pseudo sync signal having a predetermined amplitude and a predetermined width is opposite to the horizontal sync signal. Superimposed in the direction (reverse polarity). This superposition is performed not on the entire horizontal synchronizing signal but on the horizontal synchronizing signal of a predetermined number of lines within a predetermined period. That is, the period in which the pseudo synchronization signal is superimposed and the period in which the pseudo synchronization signal is not superimposed are alternately repeated. Next, the phase of only the video signal during the period in which the pseudo synchronization signal is superimposed is inverted. This becomes a scrambled video signal. A timing signal for scrambling decoding on the receiving side is superimposed on the audio signal by amplitude modulation. In order to charge for reception, the so-called downstream signal includes decoding data. An RF video signal amplitude-modulated by the video signal on which the pseudo-synchronous signal is superimposed, an RF audio signal frequency-modulated by an audio signal on which the timing signal is superimposed, and a downlink signal including decoding data are transmitted.

(2) Reception side Each of the received RF signals is converted into a video intermediate frequency signal and an audio intermediate frequency signal. A signal obtained by demodulating the video intermediate frequency signal (a video signal on which a pseudo-synchronous signal is superimposed) is decoded by a descrambler. This decoding is performed as follows. The audio intermediate frequency signal is subjected to AM detection to extract a timing signal and amplify it to a predetermined level. Based on this timing signal, a scramble decoding signal is generated and sent to the switching circuit. This switching circuit is turned on only when a predetermined reception contract has been made. Whether or not the switching circuit can be turned on is controlled by the control unit according to the decoding data in the down signal. When the switching circuit is off, the video signal is not scrambled and the audio is muted. When the switching circuit is on, a scramble decoding signal is sent to the descrambling section, so that the video signal is scrambled and the audio mute is released. In addition, it is displayed on the display unit during scramble broadcasting.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a television signal scrambling method according to the present invention will be described with reference to the drawings, taking a CATV as an example. FIG. 1 is a main block diagram showing an embodiment of a transmission-side scramble signal generation by a television signal scramble system according to the present invention, FIG. 2 is a principle waveform diagram of a video signal and an audio signal at the time of scramble, and FIG. FIG. 4 is an explanatory diagram relating to a scramble decoding signal according to an embodiment of a method for receiving a broadcast signal according to the system, FIG. 4 is a conceptual diagram when a scrambled video signal according to the present scramble system is displayed. In FIG. 1, 1
Is a video signal generator that generically refers to a video signal source such as a VTR, LD (laser disk) or video camera, 2 is a pseudo-sync signal addition unit that generates a pseudo-sync signal and performs a predetermined superimposition,
3 is a video signal inverting section, 4 is an audio signal generating section corresponding to the video signal generating section, 5 is an FM modulating section, 6 is a timing signal for use in detecting a superimposed position of the pseudo synchronizing signal. A timing signal adding section for AM-modulating the modulated wave with the timing signal and superimposing the same; 7, a scramble timing controller for controlling the superimposition timing of the pseudo-synchronous signal and the timing signal; 8, an AM modulator for video signals; A signal / sound signal mixer 10 is a channel converter.

In FIG. 3, reference numeral 31 denotes a CATV converter for converting a channel signal selected from an RF signal into video and audio intermediate frequency signals, and 32 a video signal band for passing a video intermediate frequency (VIF) signal. A pass filter (BPF); 33, a video demodulation circuit; 34, a descrambling unit for performing scramble decoding; 35, a video amplifier; 36, an audio signal band-pass filter (BPF) for passing an audio intermediate frequency (SIF) signal; Is an audio FM demodulator, 38 is an audio multiplex demodulator, 39 is an electronic volume (VR) for volume adjustment,
40 is an audio amplifier, 41 is a timing signal detection unit, 42 is a timing signal amplification unit, 43 is a scramble decoding signal generation unit, 44 is a switching circuit, 45 is a timing signal presence / absence determination unit, 46
Denotes a downlink signal (eg, FSK) demodulation unit, 47 denotes a control unit (generally a microcomputer), and 48 denotes a display unit.

Next, the operation of the present invention will be described separately for generation of a scrambled signal on the transmitting side and decoding of the scrambled signal on the receiving side. (1) Generation of a scramble signal on the transmission side (FIG. 1) The scramble of the video signal is to have a waveform shown in FIG. 2 (A). As shown in FIG.
Is superimposed on the back porch portion of the horizontal blanking period Tb. FIG. 3A shows the waveform after inverting the video signal during the superimposition period (video signal inverting unit 3), so that the superimposition of the pseudo synchronizing signal in the pseudo synchronizing signal adding unit 2 is performed in the opposite direction, that is, the horizontal synchronizing signal. The direction is opposite to (b) (FIG. C-1 below). The symbol (c) in the figure is a color burst signal.

(C) is an enlarged view of the period of one horizontal cycle.
FIG. 3 (C-1) shows the superimposition of the pseudo synchronizing signal in the pseudo synchronizing signal adding unit 2, and FIG. 2 (C-2) shows the superimposed pseudo synchronizing signal after inversion by the video signal inverting unit 3. FIG. In FIG. (C-1), the time and the amplitude are described in the main part such as the pseudo sync signal, but the pulse width and the amplitude of the pseudo sync signal are merely examples. As described above, the pseudo synchronizing signal adding unit 2 generates a pseudo synchronizing signal having a predetermined pulse width and amplitude, and superimposes the pseudo synchronizing signal as shown in FIG. Rather than performing the superimposition, the superimposition is performed on the horizontal retrace period existing within a predetermined period, and the superimposition is not performed during the subsequent predetermined period. That is, superimposition and non-superposition of the pseudo-synchronous signal are alternately repeated. FIG. 2A shows this repetition in a superimposed period 3H (H: 1 horizontal cycle) and a non-superimposed period 3H.
This is an example. The superimposition period and the non-superposition period are arbitrary.

The control of superimposition and non-superposition of the pseudo synchronizing signal as described above is performed by the scramble timing controller 7 based on the input synchronizing signal S1 (horizontal and vertical). Assuming that the period in which the pseudo synchronization signal is superimposed is Ts (FIG. 2A), only the video signal (including the horizontal synchronization signal) in the period of Ts is inverted in phase by the video signal inversion unit 3. This phase inversion only during the period of Ts is performed under the control of the scramble timing control unit 7. FIG. 2A shows the output waveform of the video signal inverting section 3, which is a scrambled video signal. The output of the video signal inverter 3 is amplitude-modulated by the video signal AM modulator 8 in the same manner as a conventional television video signal.

A timing signal necessary for decoding the scramble signal on the receiving side is transmitted by being superimposed on the audio signal. In other words, after the signal from the audio signal generation unit 4 is subjected to frequency modulation (FM) processing in the same manner as the conventional television audio signal, the timing signal addition unit 6 performs the Ts period (scrambled video period).
Only the timing signal is superimposed by amplitude modulation (AM) means. FIG. 2 shows such a superimposed state.
(B). As shown in the figure, the pseudo-sync signal (a) is made coincident with the start point of the superimposed horizontal blanking period, and the cycle is the same as the pseudo-sync signal (that is, the horizontal cycle). The reason for this matching is to enable the receiving side to easily detect the scramble start point. The audio signal on which the timing signal is superimposed as described above is mixed with the signal from the video signal AM modulator 8 by the mixer 9, and the mixed signal is converted into an RF signal of a predetermined frequency by the channel converter 10. Send. By the way, in the present scramble system, a data signal for decoding is required in addition to the video signal and the audio signal so that only the authorized subscriber can decode the scramble signal as in the conventional pay broadcast reception. However, the decoding data signal itself is transmitted together with the RF signal in a downlink signal transmitted from a broadcasting center, as in the related art. Although there are several types of signal systems for the downlink signal, in this embodiment, FSK (Frequency Shift Keying) is used.

(2) Decoding of a scrambled signal on the receiving side FIG. 3 illustrates a conventional functional block and a functional block for descrambling the signal by the method according to the present invention. The video and audio RF signals and the downlink signal described in the preceding section are selected and received by the CATV converter 31, the converted intermediate frequency signal is sent to the VIF BPF 32 and the SIF BPF 36, and the downlink signal is sent to the FSK demodulator 46. Sent to The video intermediate frequency signal extracted by the VIF BPF 32 demodulates the original video signal by the video demodulation circuit 33 and sends it to the descrambling unit 34. Also, BPF for SIF
The audio intermediate frequency signal is extracted at 36, and the audio FM demodulator 37,
An original audio signal is obtained by a conventional circuit such as the audio multiplex demodulator 38, the electronic VR 39, and the audio amplifier 40.

On the other hand, the audio intermediate frequency signal is input to a timing signal detector 41, and the timing signal (FIG. 2B) superimposed on the FM audio signal is detected by AM detection and extracted. The extracted timing signal is amplified to a predetermined level (amplifying unit 42), and then sent to a scramble decoding signal generating unit 43. The purpose of the scramble decoding signal generator 43 is to generate the scramble decoding signal shown in FIG. B from the timing pulse (d) shown in FIG. Since the width of the extracted timing pulse is several μS (about 4 to 5 μS), it is extended to a width of 1H (eg, 63.5 μS) for each pulse, and this extension is performed for the number of timing pulses. Obtain the waveform of The pulse start point in FIG. B is the scramble start point, and its width Td matches the scramble period (Td = Ts).

The scramble decoding signal thus obtained is sent to the switching circuit 44. The switching circuit 44 is turned on / off under the control of the control unit 47. Scramble broadcasting is generally charged, so that only authorized subscribers can receive it. Whether the switching circuit 44 is turned on or not can be determined from the specific data corresponding to the presence or absence of the reception contract included in the downlink signal, so the control unit 47 determines the specific data in the demodulated signal from the FSK demodulation unit 46, Turn on or off. Therefore, when the reception is not contracted, the switching circuit 44 is not turned on and the scramble decoding is not performed. Scramble decryption is performed. That is, the pseudo synchronizing signal is removed from the video signal during the period Td of the signal, and the phase of the signal is returned from the inverted state to the normal phase. Thus, the scrambled signal is decoded and becomes a normal signal, and a video signal of a predetermined level is obtained through the video amplifier 35.

Further, when the timing signal is detected by the timing signal detecting section 41, the received broadcast is a scrambled broadcast, so that it is convenient to display that fact. Therefore, the timing signal presence / absence determination unit 45
To determine the presence or absence of a timing signal, and sends the determination data to the control unit 47. When there is a data input indicating that the timing signal exists, the control unit 47 displays the data on the display unit 48 to notify the user that the broadcast is a scrambled broadcast. In addition,
The control unit 47 generally uses a microcomputer. As described above, the audio signal of this system can be normally demodulated even in the case of scrambled broadcasting. Therefore, a method of muting the audio during scrambling may be used together. Whether or not to apply the audio mute can be determined based on the presence or absence of the timing signal as in the case of the above display. That is,
When the control unit 47 receives a data input from the timing signal presence / absence determining unit 45 indicating that a timing signal exists, the electronic VR
(As an example) to mute audio. still,
FIG. 5 is a conceptual diagram when a scrambled video signal according to the present method is projected. FIG. 5 shows the original video signal as one vertical bar for easy understanding (FIG. A). And
At the time of scrambling, as shown in FIG. B, the image is shifted from the horizontal position during the normal period and inverted between black and white in every scrambling period, and it looks as if horizontal jitter is caused. (A) shows the non-scrambled part, and (B) shows the scrambled part.

[0017]

As described above, the present invention provides one new system which has not been available in the past. At present, a scrambling method such as the core tech method or the skyport method is adopted in the field of satellite broadcasting, but this method can perform scrambling with a simpler configuration than these methods. Therefore, both the transmitting side and the receiving side can be configured by simple circuits.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing an embodiment on a transmitting side of a television signal scrambling system according to the present invention.

FIG. 2 is a waveform diagram at the time of scrambling for explaining a television signal scrambling method according to the present invention.

FIG. 3 is a main block diagram showing an embodiment of a signal receiving method based on a television signal scrambling method according to the present invention.

FIG. 4 is a waveform diagram of a scramble decoding signal for explaining FIG. 3;

FIG. 5 is a conceptual diagram when a scrambled video signal based on a television signal scrambling method according to the present invention is displayed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video signal generation part 2 Pseudo synchronization signal addition part 3 Video signal inversion part 4 Audio signal generation part 5 FM modulation part 6 Timing signal addition part 7 Scramble timing control part 8 Video signal AM modulation part 31 CATV converter 32 Video signal Bandpass filter (BPF) 33 Video demodulation circuit 34 Descrambler 36 Bandpass filter for audio signal (BPF) 41 Timing signal detector 42 Timing signal amplifier 43 Scramble decoding signal generator 44 Switching circuit 45 Timing signal presence / absence detector 46 Downlink signal demodulation unit 47 Control unit 48 Display unit

Claims (4)

(57) [Claims] 1. A television signal configured to transmit an amplitude-modulated video signal, a frequency-modulated audio signal, and a downstream signal of a predetermined modulation related to transmission of required data,
A pseudo-synchronous signal having a predetermined amplitude and a predetermined pulse width is generated, and the pseudo-synchronous signal is provided at a back porch position of a horizontal retrace period of the video signal in a reverse polarity to the horizontal synchronizing signal for a predetermined number of horizontal lines every predetermined number of horizontal lines Means for superimposing the pseudo synchronizing signal on the video signal;
A phase-inverted scrambled video signal, a timing signal superimposed audio signal obtained by amplitude-modulating and superimposing a timing signal generated for use in detecting a vertical position of the pseudo-synchronous signal on the audio signal, and the scrambled video signal A scramble system for a television signal, wherein the down signal including data indicating the following is transmitted. 2. A descrambling unit for descrambling the scrambled video signal 2 obtained by demodulating a video intermediate frequency signal obtained by frequency-converting a received RF signal when receiving a transmission signal according to the scrambling method; A timing detector for detecting the timing signal by AM detecting an audio intermediate frequency signal obtained by frequency-converting the signal, an amplifier for amplifying the timing signal detected by the timing signal detector, and a timing signal amplified by the amplifier Video signal period in which the pseudo sync signal is superimposed based on
Scrambled decrypted signal with the matched pulse width between
A scrambling decryption signal generator for generating said type scramble decrypting signals, at the time on sending the scrambled decrypted signal to the descrambling unit, switching to stop delivery of the scrambled decrypted signal at the time of OFF Circuit, and a control unit for controlling the switching circuit to be turned on or off from specific data included in the demodulated data of the downlink signal obtained from the RF signal, and scrambles only when the switching circuit is turned on. 2. The transmission signal receiving method according to claim 1, wherein the scramble decoding of the video signal is performed by the descrambling unit. A timing signal presence / absence determination unit for determining whether a timing signal is detected by the timing signal detection unit; a control unit configured to input a determination signal from the timing signal presence / absence determination unit; and a display unit constituting a display under the control of the control unit is provided, receiving scheme of claim 2, wherein at the time of scrambling a video signal, characterized in that so as to display on the display unit. 4. A control section for controlling the switching circuit to turn on or off, wherein when the switching circuit is turned off, the sound mute is applied at the same time, and when the switching circuit is turned on, the mute section cancels the sound mute. 3. The receiving method according to claim 2, wherein the circuit is controlled.
Expression .