JPS61214881A - Sound multiple signal transmitting system for chargeable television broadcasting - Google Patents

Abstract

PURPOSE:To make an exclusive-use modulator unnecessary at both the transmitting and receiving sides and to make the circuit constitution simple by modulating frequency data to show the carrier frequency of a sub-sound signal by the modulating system different from that of the main sound signal for the main sound carrier, and transmitting to the receiving side. CONSTITUTION:A sub-sound signal introduced from a sub-sound input terminal 10 is modulated by an FM transmitter 11 with the signal of an empty frequency in an FM radio frequency band as a carrier, and the parallel code of 8 bits, at a frequency code preparing circuit 12, is sent to a parallel and serial converting circuit 13. The circuit 13 derivates successively the frequency of 8 bits one by one for each 1 H period by a timing pulse from a pulse generating circuit 4. The frequency data F is synthesized by the timing away from an index pulse I from the circuit 4 for a constant time T0 only and impressed as a modulating input of an AM modulator 9. The output of the modulator 9 is mixed with the output of a scrambling circuit 5, and converted and transmitted to a prescribed TV channel signal by an up-converter 6. On the other hand, the signal is demodulated by the reverse procedure with the transmitting side at the receiving side.

Description

[Detailed description of the invention]

(B) Industrial Application Field The present invention relates to a pay TV (television co-system C) such as CATV, and a method C for transmitting audio multiplexed signals in this system C. ) Conventionally, pay TV broadcasting based on CATV has been popular in the United States, Canada, etc., and it seems that audio multiplex broadcasting is desired even in such pay TV system areas. ; It has become. However, in the pay TV systems of these countries, the scrambled and transmitted T''/video signal is transmitted using an audio carrier wave that is descrambled data for descrambling on the receiving side. Currently adopted in Japan and other countries, it is a sub-audio signal, and the Japanese system is FMf.
The VI4 sub-audio signals are each frequency-multiplexed with the main audio signal 1, and the frequency-multiplexed audio signal is used to FM-modulate the audio carrier wave before being transmitted. This is because if AM modulation is applied using the above-mentioned cancellation data of the audio carrier wave i, the bandwidth of the modulated signal will widen, and there is a risk that the audio signal band g2 of the TV channel will not fit. For this reason, the above-mentioned pay TV system 1;
For example, Japanese Patent Application Laid-open No. 55-141873 C; as shown, the video signal and main audio signal of each channel are transmitted as they are on \T''/channel, and the sub audio signal corresponding to this channel ≦2 is transmitted in the IFMFM radio band. No. C: It has been proposed to convert and transmit. By the way, in the case of this method, which frequency of the FM radio band is modulated as a carrier wave for the sub-audio signal of each television channel? [i.e. It is necessary to transmit the carrier frequency (C: reception, side F2) for each of the above TV channels. Therefore, information indicating the carrier frequency of such a sub-audio signal (hereinafter referred to as single frequency data) is A conceivable transmission method is to use this frequency data to Ei'M modulate a frequency near the main audio carrier wave as a carrier wave.However, in this case, even in C2, AM modulation is performed using cancellation data as described above. Since the frequency band occupied by the main audio carrier wave is expanding, the carrier wave for frequency data modulation is selected and transmitted within the band of the corresponding 'IV channel. Furthermore, even if it were possible, a separate C; modulator and receiver would be required for transmitting and receiving the frequency data.
There is also the problem of requiring a liI device. (C) Problems to be Solved by the Invention The bottle of the present invention has been made to solve the drawbacks of the conventional system described above, and it is possible to convert the above-mentioned frequency data indicating the carrier frequency of the sub-audio signal into the carrier frequency of the main audio signal. Descramble data etc.C
The present invention aims to provide a method for reliably transmitting audio signals with a simple configuration without condescending to the same adverse effects. The main audio carrier wave, which is the frequency data indicating the frequency, is modulated using a modulation method different from that of the main audio signal and transmitted to the receiving side 1. (E) Operation According to the above configuration C, one frequency data is multiplexed with the main audio signal and the video signal as a main audio carrier and transmitted through the nTV channel C; (F) Embodiment FIG. 1 shows a schematic configuration of a transmitting side device of a CATV system to which the present invention is applied. In the same figure C, (1) is the A6 video input terminal into which the baseband TV video signal is introduced, and the video signal introduced here is inputted to the synchronous separation circuit (2) c at the other end. Then, the video signal modulation circuit (3) is inputted to the video signal IF' (intermediate frequency) carrier wave C: and thus AM modulated.The fm synchronization separation circuit (2) separates the horizontal and vertical synchronization signals from the video signal. Upon obtaining each of these synchronization signals, the pulse generation circuit (4) generates a first control pulse corresponding to a short period (hereinafter referred to as a horizontal blanking period) that includes at least the horizontal synchronization signal within the horizontal blanking period. and vertical blanking period C; a corresponding second control pulse is created.The scrambling circuit (5) obtains the first and second control pulses, works as an amplitude suppression circuit, and outputs from the video signal modulation circuit (3). Video IF' (No. 1 (No. 5I)
The amplitude of each blanking period of CK)) is compressed. At this time, this amplitude compression is performed on a portion sufficiently lower than the maximum degree of variation of the video signal portion. The output signal of the above scrambling circuit (5) is shown in Figure 3 (b).
This signal becomes the up converter (6)
t=sent. Kyu C2 (7) is the main audio input terminal into which the baseband TV main audio signal is introduced, and the main audio signal introduced here is converted into audio IF carrier C by the main audio signal modulation circuit (8).
After being tuned to FM by the second circuit, the AM modulation circuit (9) is powered by the second circuit. On the other hand, (1G is a sub-audio input terminal into which a TV sub-audio signal is introduced; FM transmission a (Ll)
It is modulated and output. Simultaneous value: This carrier signal from the FM transmitter αυ is input to the frequency code generation circuit α'Jc, from which an 8-bit parallel code representing the frequency of the carrier signal is output as frequency data, and this data ( court signal]
is sent to the parallel/serial converter circuit (13I). The parallel/serial converter circuit (13 is a timing pulse from the pulse generating circuit (4)) and outputs a predetermined 8H (H is one horizontal period) within one field. Period C of each 1H: 1 bit (1 digit) i'' of the 8-bit frequency data is sequentially derived. At this time, the period of 8H can be arbitrarily selected from within 1 field. For example, the period from the 22nd to the 29th H in each field can be used. Also, the timing at which each pulse of the frequency data is generated within each 1H period is determined by the pulse l''! formation circuit (4). The timing is a certain time interval (To) away from the peak of the index pulse output from the index pulse (I). 4) is an example of serially converted frequency data 0, which is a frequency value obtained from the 8-pit code [11010011)c. (MHz).Then, this frequency data (0 and the above index pulse (I)
The waveforms are shown together as pulse train C in Fig. 4(e). This pulse train is given as a modulation input to the AM modulation circuit (9), and AM modulation is applied to the audio IF signal C output from the main audio signal modulation circuit (8). Therefore, the output signal of this AM modulation circuit (9) has a range as shown in FIG. 3 (c), and this signal (c) is
) [FIG. 5(B)] and is mixed with the output signal of the TV channel signal I (FIG. 5(B)) and frequency-converted into a predetermined TV channel signal I in the above-mentioned up converter (6). This TV channel signal is an FM-modulated sub-audio signal (hereinafter referred to as an FM sub-audio signal) output from the FM transmitter a1).
and FSK modulated IIFIJ from data transmitter I
It is frequency multiplexed with the 1fl data signal and transmitted to the receiving side via a cable (not shown). Here, the data transmitter (L9 is a computer etc.
Therefore, the data input terminal (1) is created to transmit various control data for each subscriber and each program using a predetermined empty channel frequency within the TV band. As the points are not directly related to the present invention, further explanation will be omitted. , (2I) is an input terminal into which a received signal is introduced, and the TV signal in the received signal is input to the tuner 1221 into a specific channel (
For example, signal C of the third channel]: After being frequency-converted, it is inputted to the video signal extraction circuit Q66 at -1000, and inputted to the audio signal extraction circuit 1241c at the other side. The output signal of the audio signal extraction circuit @ (Fig. 5 (b)) is inputted by the AM detection circuit 1#, and the pulse train signal (Fig. 5 (c)) is demodulated by the AM detection circuit C2. ) is input to the gate circuit.This gate circuit receives the gate pulse (shown in the same figure) from the timing pulse generation circuit, which will be described later, and generates the index signal (D) in the pulse train signal (c). The index signal (I) is given as one input of the phase detection circuit (to).The fHC from the pulse generation circuit is also given as the other input of this phase detection circuit.
A pulse signal of 1,000 horizontal numbers is given. The output of the above phase detection circuit (to) is 32f! of the vCO (*pressure controlled oscillator) 121', and thus the 32/! from this VCO.
A combination of a counter, etc. that counts the pulses of I;
A PLL (phase locked loop) is configured. In addition, (to) is a vertical detection circuit to which the output signal of the above gate circuit is given, and the vertical blanking period in the output signal of the above gate circuit.

[ ; is used to detect the above blanking period by making use of the fact that the index signal peak does not exist, and use the detection output to reset counter 1 in the pulse generation circuit. . Incidentally, the detection of index No. 111 by the detection circuit (2) is performed by sampling with horizontal period pulses from the timing pulse generation circuit (2). Missing C2, (3D is a frequency data detection circuit, and the above A
The output signal of the M detection circuit (fifth factor (c)) is converted to a monostable multivibrator, etc., using a signal with a slightly wider tolerance (the same figure (
)) C conversion and convert this signal to each 1H of @22nd to 29thH.
The timing pulse generation circuit (
2) Sampling at the timing of the pulse (G) generated from C2, extracting frequency data (0),
The extracted data (CF) is given to the microcomputer (to) C for channel selection. Also,? The output signal 9 (FIG. 5 (a)) of the image signal extraction circuit (to) is supplied to the gain switching circuit (C), and this switching circuit (to) 62 is generated from the timing pulse generation circuit. Switching signal (su)
is applied, and during the high level period of this signal C2, the amplification gain of the switching circuit C2 is switched to increase. Here, the interval (Tl) (T2) of the above switching signal (su)
Since the horizontal blanking period and the vertical blanking period described on the transmitting side coincide with each other, the carrier video signal output from the gain switching circuit is horizontal to the video signal section as shown in Figure 5. This becomes a signal in which the relative gain difference with the vertical image blanking period has been eliminated. Then, this carrier video signal is outputted from the audio signal extraction circuit (2).
'M is mixed with the main audio signal and sent to the TV receiver's antenna terminal (:).Meanwhile, the channel selection microcomputer controls the tuner to receive the selected TV channel. When controlling, the corresponding TV channel i is being received.
When the reception of the corresponding sub-audio signal is designated by the above-mentioned E(B)C; the frequency data extracted by the 1-frequency data detection circuit ctnc is decoded. and 1
When the channel selection microcomputer (2) decodes this and detects the carrier frequency of the sub-audio signal, it switches the main audio/sub-audio switching circuit (to) to the sub-audio side.
Receiving circuit t37) t"The aforementioned detected carrier frequency range -
Synchronize. As a result, the FM sub-audio signal corresponding to the receiving channel inputted from the input terminal (21) is transferred to the switching circuit (2) and the IJ transmitter c161t.
M receiving circuit CI? ), the baseband audio signal C: is demodulated and sent to a speaker device, etc. outside the TV receiver. In addition, when the channel selection key (to) [; is used to select only the channel and not specify sub-audio reception, or when sub-audio reception is specified but the sub-audio broadcast corresponding to the current receiving channel C2 is not specified. When the frequency code does not exist, that is, when the frequency code is not detected by the frequency data detection circuit 13D, the channel selection microcomputer Ga switches the main audio/sub audio switching circuit C (5111' main audio side (E) C; c, F
The M receiving circuit c (7) is tuned to the carrier frequency (corresponding to the sixth channel C) C2 of the FM main universal signal output from the audio signal extracting circuit □□□. Therefore, in this case, FM
The main audio signal is output from the receiving circuit Gη. In addition, (to) is a demodulation circuit that demodulates 6-signal type control data to the FS received by the tuner, and various control data is obtained from this demodulation circuit to the tuning microcomputer (34 is for each subscriber). C: is set to control whether reception is possible or not for each person, each channel, and each program.Here, as mentioned above, when sub-audio reception is specified,
External speaker device 1 from the FM receiving circuit C(7): Apart from the sub-audio played back from the external speaker device 1, the main audio is played from the TV receiver speaker. If a stereo broadcast is configured with
All you have to do is mute the main audio on the V receiver side. Further, in the above embodiment, the carrier video signal is scrambled by amplitude compression C in each horizontal and vertical blanking period, and the descrambled data to be modulated and multiplexed with the main audio carrier C is transmitted during the horizontal blanking period. C: Index pulses with matched phases are used, but scramble 1 and main audio carrier C: Of course, the above canceling data to be modulated and multiplexed may be other than that, and it represents the frequency of the required C secondary audio carrier. The child station wave number data may be multiplexed with the main audio carrier g-modulation at a time position different from the cancellation data. In addition, if the audio signal is AM-modulated, it is possible to modulate and multiplex it onto the main audio carrier using descrambling data and sub-audio carrier frequency data gF'M modulation. . (G) Effects of the Invention According to the audio multiplex signal transmission system C of the present invention, the main audio carrier wave is modulated and multiplexed with slave station wave number data representing the carrier frequency of the TV sub audio signal. Therefore, the descrambled data of the video signal is transferred to the main audio carrier C:
In the case of multiplexing I: the above frequency data can be sufficiently multiplexed within the audio signal band of the TV channel;
Ta. Since the frequency data is modulated and multiplexed onto the main audio carrier wave using a method different from the modulation method of the main audio, the main audio signal is not affected in any way. Moreover, since a separate carrier wave is not used for modulating one frequency data, there is no need for a dedicated modulator and demodulator for the transmitting side and the receiving side 5, respectively. Therefore, there is an advantage that one circuit configuration can be simplified.

[Brief explanation of the drawing]

Claims (2)

[Claims] (1) A pay television system in which, in addition to the video signal and main audio signal that are transmitted as a television signal for one channel, a sub-audio signal corresponding to that TV channel is transmitted using a frequency outside the channel as a carrier wave. In the broadcasting system, data representing the carrier frequency of the sub-sound is modulated onto the carrier wave of the main sound using a modulation method different from that of the main sound, and then transmitted. Audio multiplex signal transmission system. (2) The audio multiplex signal transmission system according to claim 1, wherein the data is transmitted by applying AM modulation to a main audio carrier wave that has been FM-modulated with a main audio signal.