JPS6151667A - Pcm audio service system - Google Patents

Abstract

PURPOSE:To prevent PCM audio service from tapping with a simple structure by making the specified conversion of the format of a synchronizing signal of a PCM audio signal, transmitting, and restoring it to the original form after receiving. CONSTITUTION:The synchronizing signal of the PCM signal from a compact disc player 11 for broadcasting is converted to the format, which has more than 12 bits of consecutive ''1'' or ''0'' and is 22 bits of the entire length, through a scramble encoder 12, superposed with the PCM audio signal in a modulator 13, and transmitted through a TV line. The synchronizing signal extracted from a demodulator 14 in a receiving device is converted to the original format by a scramble decorder 15, which has 11 bits of consecutive ''1'' or ''0'', to be supplied to the compact disc layer 16. With this specified conversion of the format, it permits to prevent the PCM audio survice form tapping with a simple structure.

Description

[Detailed description of the invention] [Industrial application field]

The present invention mainly relates to a PCM audio service system for CATV systems.

[Conventional technology]

As a system of this kind, the one shown in FIG. 1 is known. Here, it is possible to extract an EFM format signal using a compact disc player 1 for broadcasting, and this signal is added to a modulator 2, folded into an audio signal, and sent out via a CATV line. On the receiving side, the EFM signal is demodulated by a demodulator 3, and is added to a compact disc player 4 to obtain a PCM audio output. [Technical Issue] The problem here is that if compact disc players compatible with 0ATV become popular in multi-value formats, the problem of eavesdropping on PCM audio broadcast for a fee will occur. In this case, conventional demodulators are easy to manufacture, and it is difficult to prevent eavesdropping in this system. [Object of the invention] The present invention was made based on the above circumstances, and
When performing M-audio service, scrambling to prevent eavesdropping can be achieved with a simple (direct configuration), and J5 is installed on the terminal.
The purpose of the present invention is to provide a PCM audio service system that descrambles and outputs official 10M audio. Structure 1 of the Invention For this purpose, the present invention modulates a PCM signal in a PCM format written on a compact disc, and modulates the PCM signal with a body length of 22 bits so that the number of consecutive 1's or O's is 12 bits or more at maximum. This system is characterized in that a synchronization signal having a format of 1M is extracted and converted on the receiving side into an original formal synchronization signal in which a series of 1's and 0's each constitutes an 11-bit length format. (Embodiment 1 Hereinafter, an embodiment of the present invention will be explained in detail with reference to FIGS. 2 to 4. In the figure, d5 and numeral 11 are
This is a compact disc player for broadcasting stations that has a signal output.The EFM signal outputted here is scrambled by a scramble encoder 12, applied to a modulator 13, and multiplied into a PCM audio signal to be transmitted to a CATV.
sent to the line. On the receiving side (terminal), the EFM signal is extracted by a demodulator 14 and can be input into scrambled data 15. Then, CATV is transmitted using the descrambled EFM signal.
The corresponding combinations 1 to 16 output PCM audio. The scramble encoder 12 and decoder 15 have a configuration as shown in FIG. 4. Here, E
The FM signal is input to the shift register 32 from a, the clock component is extracted to the PLL circuit 31, and the clock signal is input from b. For example, as shown in FIG. 3, the regular EFM signal has an 11-bit length "
The frame is determined to be a 22-bit long frame consisting of a 11-bit OII and a 12-bit long OII.
When converted to a 22-bit frame consisting of pit length "O", the compact disc player 1
1 will not work properly. Therefore, for scrambling, when modulating on the transmitting side, the above 11111 or O'' is made to be longer than 12 bits.For such processing, the bit length of the shift register 32 needs to be 23 bits or more. As shown in FIG. 4, when the synchronization signal from the compact disc player 11 is input to the shift register 32, it is detected by the synchronization signal detector 33 and provides information to the control section 34. The output of the control section 34 is fed back to the shift register 32, changes the state of the flip-flop in the shift register 32, and converts the synchronization signal from a normal signal to a scrambled signal.This control section 34 includes a PLL circuit. The lock component is given from 31. The above is how it is used as a scramble encoder. As a scramble decoder, the scrambled EFM signal is input to the shift register 32, and the scrambled EFM signal is input to the shift register 32, °"Q II It is converted into a format consisting of a5 and "1'° frames. At least the main part of the circuit configuration shown in FIG. 4 is desirably implemented in LSI to prevent eavesdropping. In the following, the 0ATV system is explained as an audio service system, but it is of course applicable to other wireless systems. [Effect 1 of the Invention] As detailed above, the present invention For audio,
Since an EFM signal scrambler and descrambler are introduced, there is an advantage that eavesdropping can be effectively prevented even if a player compatible with 0ATV is involved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional example, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a frame configuration diagram of an EFM signal, and FIG. 4 is a detailed block diagram of main parts. 11...Kombaku 1 disk player for broadcasting, 12.
... Scramble encoder, 13 ... Modulator, 11
Toad...Salt 5 circuit generator, 15...Scramble decoder,
1G...compact disc player, 31...P
LL circuit, 32... shift register, 33... synchronization signal detection section, 34... control section. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] The PCM signal in the PCM format written on the compact disc is modulated, a synchronization signal is extracted that has a format with a total length of 22 bits so that the number of continuous 1s or 0s is at least 12 bits, and this signal is transmitted to the receiving side. 1. A PCM audio service system, characterized in that a series of 1's and 0's, respectively, is converted into a synchronizing signal constituting an 11-bit length format.