JP2007306627A - Information conversion apparatus and information conversion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To distribute a program broadcast in a digital satellite broadcast to a plurality of cable television networks at a low cost. <P>SOLUTION: A demodulation means 421 demodulates a digital signal received by a reception means for receiving the digital signal distributed from a center station and modulated by a prescribed modulation system, and a transmission information conversion means 423 for rewriting an NIT included in the signal demodulated by the demodulation means 421 into an NIT for cable television deletes signals not retransmitted from the digital signals distributed from the center station and embeds dummy data to the deleted signals. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information replacement device and an information replacement method.

  Recently, so-called cable television has begun to spread as multi-channel media even in remote areas and difficult viewing areas. FIG. 30 illustrates an example of a cable television receiver. The data receiving unit 71 extracts a receiver control signal from the cable television signal transmitted from the cable television station and supplies the signal to the host processor 72. The cable TV signal is an analog signal. The host processor 72 controls the entire receiver based on the receiver control signal and the viewer's channel selection operation. The reception tuner 73 extracts the signal of the program selected by the viewer from the cable TV signal and outputs it to the descrambler 74. The descrambler 74 uses the synchronization signal supplied from the AM detection circuit 77 to release the scramble of the program signal and outputs it to the video detection circuit 75 and the AM detection circuit 77. The video detection circuit 75 extracts and demodulates the video signal from the program signal, and outputs the remainder of the program signal to the FM detection circuit 76. The FM detection circuit 76 demodulates the audio signal.

  As described above, in cable television, information (video signal, audio signal, and control signal) is transmitted as an analog signal. Accordingly, since the information cannot be compressed and multiplexed, the number of channels (programs) that can be supplied on the cable television is about 60 channels.

  By the way, in the digital multi-channel satellite broadcasting (for example, PerfecTV (trademark)) that is now widely used, broadcasting of 100 channels or more is realized, and as the market needs, even more multi-channels are provided for cable TV. Is desired.

  Now, in order to realize further multi-channeling in cable television, it is conceivable to compress and multiplex video by digitizing all signals in the cable television station. It is difficult to realize this, considering the capital investment and running cost. Thus, a method for realizing further multi-channel in cable television by redistributing digital multi-channel satellite broadcasting such as PerfecTV to the cable television network is conceivable.

  Here, the digital multi-channel satellite broadcasting system will be described with reference to FIG. The transmitter 111 of the satellite broadcast service provider 101 scrambles the MPEG-compressed program information supplied from the program provider, and provides electronic program guide information (EPG: Electoric Program Guide), viewer management information, etc. And transmitted to the communication satellite 102 as a linearly polarized CS wave. This CS wave is received by the CS antenna 181 via the communication satellite 102 and supplied to the receiver 182. The receiver 182 extracts predetermined program information from the CS wave and outputs it to the television receiver 106. The viewer management unit 112 issues an IC card 160 to the viewer. The key management unit 113 of the viewer management unit 112 manages a viewable program corresponding to the IC card 160. The viewing information processing unit 114 calculates a viewing fee based on the viewing information notified from the receiver 182 and notifies the customer management unit 115 of the calculated viewing fee. The customer management unit 115 charges the viewer for a viewing fee.

  FIG. 32 shows a detailed configuration of the receiver 182. The reception tuner 192 of the satellite front end unit 191 extracts a transport stream (TS: Transport Stream) including a predetermined program from the CS wave and outputs it to the QPSK demodulation circuit 193. The QPSK demodulation circuit 193 performs QPSK demodulation on the input TS and outputs the result to the error correction circuit 194. The error correction circuit 194 corrects the error information of the input TS and outputs it to the transport unit 155. The descrambler 156 of the transport unit 155 uses the descramble information recorded on the IC card 160 issued by the satellite broadcast service provider 101 to the TS scrambled by the transmission unit 111 of the satellite broadcast service provider 101. The data is decoded (descrambled) using the data and output to the demultiplexer 157.

  The demultiplexer 157 extracts predetermined program information based on the multiplexed program specification information (PSI: Program Specific Information) and supplies the extracted information to the MPEG decoder unit 158. The MPEG decoder unit 158 performs MPEG decompression on the input program, generates a video signal and an audio signal, and outputs them to the television receiver 106.

  The host processor 159 controls the entire receiver 182 in response to the viewer's operation, and records the received pay program information (program viewing information) on the IC card 160. Further, the host processor 159 reads the descrambling information recorded on the IC card 160 and supplies it to the descrambler 156. Further, the host processor 159 controls the communication unit 161 to notify the viewing information management unit 114 of the program viewing information recorded on the IC card 160 periodically. The viewing information management unit 114 calculates a viewing fee based on the input viewing information and notifies the customer management unit 115 of the fee.

JP 09-191453 A Japanese Patent Laid-Open No. 10-079931 JP 09-275551 A Japanese Patent Laid-Open No. 09-233459 "ETR 211 Digital broadcasting systems for television; Implementation guidelines for the use of MPEG-2 systems; Guidelines on implementation and usage of service information," European Telecommunications Standards Institute (ETSI), April 1996, First Edition, p. 1-32 "EN 300 468 V1.3.1 (1998-02) Digital Video Broadcasting (DVB); Specification for service Information (SI) in DVB systems," European Telecommunications Standards Institute (ETSI), February 1998

  However, in order to distribute the digital multi-channel satellite broadcast signal to the cable television network, the cable television station 103 receives the digital multi-channel satellite broadcast signal, separates the multiplexed signal, and multiplexes again. Processing is required and the equipment is very expensive.

  By the way, in order to provide digital multi-channel service in a plurality of cable networks, each cable network needs a device for digitizing and multiplexing a plurality of programs and a facility for customer management. Requires cost.

  In addition, since the service provision method differs for each medium such as CS digital service, BS digital service, and terrestrial digital service, it is necessary to arrange the transmission method in each cable network in order to receive these by a common receiver.

  In addition, in the system in which the service from the satellite is reconfigured and transmitted on the cable network, it is practically impossible to receive a service unique to the digital service such as an EPG service or a download service.

  The present invention has been made in view of such a situation, and an information replacement device and an information replacement method capable of distributing a program broadcast in digital satellite broadcasting to a plurality of cable television networks at a low cost. The purpose is to provide.

  An information replacement device according to the present invention includes a receiving unit that receives a digital signal distributed from a center station modulated by a predetermined modulation method, and a digital signal that is modulated by the predetermined modulation method received by the receiving unit. Demodulating means for demodulating and transmission information replacing means for rewriting NIT contained in the signal demodulated by the demodulating means to NIT for cable television, wherein the transmission information replacing means is the digital information distributed from the center station. Of the signals, signals that are not retransmitted are deleted, and the deleted signals are made up of dummy data.

  The information replacement method according to the present invention includes a step of receiving a digital signal distributed from a center station modulated by a predetermined modulation method, and a step of demodulating the received digital signal modulated by the predetermined modulation method. And rewriting the NIT included in the demodulated signal to the NIT for cable television, and deleting the non-retransmitted signal from the digital signal distributed from the center station and replacing the deleted signal with dummy data. And the step of making up for this.

  According to the present invention, a digital multi-channel service signal is distributed from a center station via a satellite line to a plurality of cable network stations, and the digital multi-channel service signal distributed from the center station via a satellite line is modulated and converted. By converting to a digital multi-channel service signal for cable transmission and distributing it from each cable network station to the receiving terminal device via the cable network, programs broadcast on digital satellite broadcasting can be transmitted to the cable TV network at low cost. Can be delivered.

The present invention is applied to, for example, an information distribution system configured as shown in FIG.

  In this specification, the term “system” means an overall apparatus constituted by a plurality of apparatuses and means.

This information distribution system receives a digital multi-channel service signal transmitted from a center station 1 that transmits program information and manages a customer, and a satellite line by a communication satellite 2 from the center station 1. a plurality of cable television station 3 ₁ to 3 _n to be transmitted to the cable television network 4 ₁ to 4 _n, composed of a plurality of receiving terminal devices 5 ₁₁ to 5 _nm which is connected to the cable television network 4 ₁ to 4 _n.

  As shown in FIG. 2, the center station 1 includes a transmission unit 11 for transmitting program information and a viewer management unit 12 for managing customers. The transmitter 11 scrambles MPEG-compressed program information supplied from a program provider and multiplexes it with service information such as electronic program guide information (EPG) and viewer management information. And transmitted to the communication satellite 2 as a linearly polarized CS wave. In addition, the viewer management unit 12 issues an IC card 60 to the viewer. The key management unit 13 of the viewer management unit 12 manages a viewable program corresponding to the IC card 60. Furthermore, the viewing information processing unit 14 calculates a viewing fee based on the viewing information notified from the receiver 6 of the receiving terminal device 5 and notifies the customer management unit 35 of the cable television station 3.

  The cable television station 3 receives the CS wave transmitted from the communication satellite 2 by the CS antenna 31, receives the radio wave of the television broadcast using the terrestrial wave by the terrestrial antenna 32, and transmits from the broadcasting satellite (not shown). Received satellite broadcast radio waves (hereinafter referred to as “BS waves”) are received by the BS antenna 33, and the distribution unit 34 mixes the input CS waves and analog broadcast waves (terrestrial and BS waves). The mixed wave is distributed to the receiver 6 of the receiving terminal device 5 via the cable television network 4. Further, the customer management unit 35 charges the viewer for a viewing fee based on the viewing fee information from the viewing information processing unit 14 of the satellite broadcast service provider 1.

  Then, the receiver 6 of the receiving terminal device 5 extracts predetermined program information from the input mixed wave and outputs it to the television receiver 7. The television receiver 7 displays the input program information.

  Here, the digital multi-channel service signal transmitted from the communication satellite 2 will be described. In this embodiment, the digital multi-channel service signal corresponds to a DVB (Digital Video Broadcasting) system. FIG. 3B shows a frame structure of digital broadcast data in the DVB system, and one frame is composed of eight MPEG2 transport packets (see FIG. 3A). In this case, the synchronization byte (= 47H) in the packet is used, and the synchronization byte is inverted (= B8H) once in 8 packets to obtain frame synchronization. Note that an error correction code according to Reed-Solomon (204, 188) is added to each MPEG2 transport packet (MPEG2TS packet). The digital broadcast data shown in FIG. 3B is further convolutionally encoded in the satellite system (in DVB, banktured code rates: 1/2, 2/3, 3/4, 5/6, and 7/8 are defined. ) Is performed, QPSK (Quadrature Phase Shift Keying) modulation is performed, and then the frequency is converted into a transmission frequency band and transmitted from the communication satellite 2 via the communication line.

  FIG. 4 shows the packet structure of an MPEG2 transport packet, and the first 4 bytes of 188 bytes form a packet header. A packet identifier (PID: Packet Identification) indicating an attribute of an individual stream (data string) of the packet is arranged in the packet header. As is well known, a PES (Packetized Elementary Stream) packet whose packet structure is shown in FIG. 5 is subdivided and arranged in the payload (data portion) of the MPEG2 transport packet, and is further defined in the MPEG2 system. Program Association Table (PAT), Program Map Table (PMT), Network Information Table (NIT) as Program Specific Information (PSI) Etc. are also arranged in section format.

  Here, PSI is information necessary for realizing a simple channel selection operation and program selection. PAT indicates the PID of the PMT that transmits the information of the packets constituting the program for each program number (16 bits), and FIG. 6 shows the table structure of the PAT. As the PID of the PAT itself, PID = “0x0000” is fixedly assigned.

  The main contents will be described. The table ID indicates the type of table, and is “0x00” (hexadecimal notation) in the PAT. TS ID identifies a stream (multiplexed encoded data), and corresponds to a transponder in the case of a satellite. The version number is added every time the contents of the table are updated. The current next indicator is used for identification when the old and new versions are transmitted simultaneously. The program number identifies each channel. The network PID indicates the PID of the NIT when the program number is “0x0000”. The program map PID indicates the PID of the PMT.

  The PMT indicates, for each program number, the PID of a packet in which a stream of video, audio, additional data, etc. constituting the program is transmitted. The PID of the PMT itself is specified by the PAT as described above. FIG. 7 shows a table structure of the PMT. The main contents not overlapping with PAT will be described. The table ID indicates the type of table and is “0x02” in the PMT. The PCR PID indicates the PID of a packet including a clock (PCR: Program Clock Reference) that serves as a reference for decoding. The stream type indicates the type of signal transmitted in the stream, such as video, audio, and additional data.

  The NIT indicates physical information on the transmission path, that is, in the satellite, the orbit of the satellite, the polarization, the frequency for each transponder, and the like. The PID of the NIT itself is specified by the PAT as described above. FIG. 8 shows the NIT table structure. Main contents not overlapping with PAT and PMT will be described. The table ID indicates the type of the table. The network is “0x40” and the other networks are “0x41”. The network ID identifies the network. In the case of a satellite, it corresponds to an individual satellite.

  When the satellite digital multi-channel broadcast signal is retransmitted on the cable television by the modulation conversion method, the NIT is rewritten. Here, a descriptor that is included in the NIT and needs to be rewritten will be described.

  First, the satellite delivery system descriptor in the satellite NIT will be described. This descriptor is used as the first descriptor repeated according to the TS (Transport Stream) descriptor length, and is paired with the TS ID.

  FIG. 9 shows the structure of the satellite delivery system descriptor. The descriptor tag is defined by DVB and indicates the type of descriptor. In this descriptor, “0x43” is set. The frequency indicates a transmission frequency for each stream (here, transponder). The orbit / west longitude / east longitude flag / polarization indicates the orbit and polarization of the satellite. The modulation / symbol rate / inner error correction coding rate indicates a specification related to the transmission method.

  At the time of re-transmission at a cable television station, the satellite delivery system descriptor is replaced with a cable delivery descriptor as shown in FIG. In the descriptor, it is “0x44”. The frequency indicates a transmission frequency for each physical channel in the cable television to be retransmitted. The modulation / symbol rate / inner error correction coding rate indicates a specification related to the transmission method. This descriptor has the same total length for the satellite and the cable and can be simply replaced.

  Next, the service list descriptor will be described. This descriptor is used as the second and subsequent descriptors that are repeated according to the TS descriptor length, and indicates the ID of the service (channel) multiplexed in the stream (here, transponder). That is, a plurality of service list descriptors are attached to one TSID.

  FIG. 11 shows the structure of the service list descriptor. The descriptor tag is defined by DVB and indicates the type of descriptor. In this descriptor, “0x41” is set. The service ID identifies a service. Usually, the service matches the channel that the viewer selects. The service type indicates the contents of the service such as video, audio, and data.

  At the time of re-transmission at a cable TV station, if the program for all transponders from the satellite is serviced within the cable, the information of this descriptor remains as it is, but it is re-transmitted when only the signal of a specific transponder is serviced The service ID of the program included in the transponder not to be deleted is deleted. In this case, dummy data is added to the information that has been deleted and reduced, so that the total length of the service list descriptor is the same as that of the satellite system, and can be simply replaced.

  The MPEG2 system stipulates that transmission of the PSI table is segmented in a format called a section. For example, the NIT is sectioned every 4 kbytes, and each section is configured in the format shown in FIG. NITs divided into a plurality of sections are related by section numbers. The total number of sections is described as the last section number in the table, and a series of NIT data until the section number matches the last section number.

  Next, a specific configuration example of the distribution unit 34 of the cable television station 3 in the cable transmission system shown in FIG. 2 will be described with reference to FIG.

  In the distribution unit 34 having the configuration shown in FIG. 12, the signal distributor 41 divides the CS wave input via the CS antenna 31 into TS (Transport Stream) for each channel, and each modulates the modulation conversion device 42-1. To 42-N (N is the number of channels included in the CS wave). The channel described above is a single propagation wave including a plurality of programs multiplexed by one transponder, unlike a channel (broadcast station) in the terrestrial wave. FIG. 13 shows an example of the state of the CS wave before being input to the signal distributor 41. That is, the CS wave H polarization includes TS1, TS3, and TS5, and the CS wave V polarization includes TS2, TS4, and TS6.

  The modulation conversion device 42 converts the input TS into a signal (QAM signal) for one channel of cable television and outputs the signal to the signal mixer 45.

  The terrestrial retransmitting device 43 RF-converts the terrestrial wave received via the terrestrial receiving antenna 32 and outputs it to the signal mixer 45. The satellite signal retransmitting device 44 receives the BS wave received by the BS antenna 33. Is RF-converted and output to the signal mixer 45.

  FIG. 14 shows a specific configuration example of the modulation conversion device 42. In the modulation conversion device 42 having the configuration shown in FIG. 14, the QPSK demodulation circuit 421 performs QPSK demodulation on the input TS and outputs it to the error correction circuit 422. The error correction circuit 422 performs error correction on the input signal and outputs the error-corrected TS to a network information (NIT: Network Information Table) conversion circuit 423.

  The NIT conversion circuit 423 indicates the NIT for CS wave (information common to all channels of the CS wave and information of the program included in the channel (propagation wave). When receiving a desired program at the receiver Is replaced with NIT for cable television and output to the QAM modulation circuit 424.

  The QAM modulation circuit 424 QAM modulates the input signal and outputs it to the frequency conversion circuit 425. The frequency conversion circuit 425 converts the frequency of the input signal into a predetermined value and outputs it to the signal mixer 45.

  The signal mixer 45 receives QAM-modulated signals input from the modulation converters 42-1 to 42-N, the terrestrial re-transmission device 43, and the satellite signal re-transmission device 44, for example, as shown in FIG. And output to the amplifier 46. The amplifier 46 amplifies the input mixed wave and supplies it to the receiver 6 via the cable television network 4.

  Here, in cable transmission, since the quality of the transmission path is better than that of the satellite line, only Reed-Solomon (204, 188) is added as an error correction code. At this time, for example, if 42.192 Mbps data is transmitted per transponder in the satellite system by encoding at a convolution rate of 3/4, 31.644 Mbps data is transmitted in the cable system. In order to transmit this amount of information with one cable channel having a bandwidth of 6 MHz, it is appropriate to use 64QAM as a modulation method. Separately, when encoding is performed at a convolution rate of 7/8 in the satellite system, data of 36.918 Mbps is transmitted through the cable system, and 128QAM is appropriate as a modulation method. The receiver 6 can receive by changing the reception method by referring to the level of the QAM modulation method for each channel in the NIT indicating the physical information of the transmission path.

  A specific configuration example of the NIT conversion circuit 423 will be described with reference to FIGS.

  As shown in FIG. 16, the NIT conversion circuit 423 includes a NIT extraction unit 440 and a NIT reinsertion unit 450 controlled by the control device 431 via the interface 432, and error correction sequentially output from the error correction circuit 422. The completed TS is supplied to the NIT extraction unit 440 and the NIT reinsertion unit 450.

  The NIT extraction unit 440 includes a NIT detection circuit 441 to which the TS is supplied, and a memory 442 that temporarily stores the NIT detected from the TS by the NIT detection circuit 441.

  As shown in FIG. 17, a specific configuration example of the NIT extraction unit 440 includes a NIT / PID filter 444 controlled by the control unit 443 and a detection performed by the NIT / PID filter 444. The NIT packet output circuit 445 outputs the NIT to the memory 442. The memory 442 includes a first-in first-out (FIFO) memory, and data writing and reading are controlled by the control device 431 via the interface 432.

  Here, when the service is provided by a plurality of satellites, the NITa (Actual Network Information Table) related to the TS in the TS and the NITo (Other Network Information Table) related to the TS transmitted by other satellites are included in the TS. There will be multiple NITs, which can be identified by the table ID. In the NIT extraction unit 440, the NIT detection circuit 441 performs NIT detection for both NITa and NITo, and writes them in the FIFO memory 442 in the order of detection. Writing to the FIFO memory 442 is performed using a write clock write_clk synchronized with TS, and detection of INT by the NIT detection circuit 441 and writing processing to the FIFO memory 442 are performed in real time. .

  The NIT extraction unit 440 performs NIT extraction processing according to the procedure shown in the flowchart of FIG.

  That is, the NIT extraction unit 440 enters an operating state when the control unit 443 receives the detection start signal start from the control device 431, and detects the NIT for each TS packet by referring to PID (= “0x0010”). Perform the action.

  The control unit 443 loads the TS packet into the NI / PID filter 444 (step S1), determines the PIT of the NIT (step S2), and when the PIT of the NIT is detected, determines whether or not it is the head data of the NIT. If it is determined (step S3) that the table ID is included in the packet in which the PID of NIT is detected, the table ID (own network “0x40”, other network ” 0x41 ″) (step S4), the NIT detected by the NIT / PID filter 444 is output from the NIT packet output circuit 445, and after the start of detection, from the head data of the first received table (In other words, the table ID) is written into the FIFO memory 442 (steps S5 and S6).

  Further, the control unit 443 determines whether or not both the NITa of its own network and the NITo of the other network have been extracted (step S7). If the extraction has not ended, the process returns to step S1. The NIT extraction process is repeated for every 188 bytes of the TS packet (step S8).

  Then, the control unit 443 detects all the NITs of both the NITa of the own network and the NITo of the other network, writes them to the FIFO memory 442, notifies the control device of the end of extraction, and ends a series of detection operations. . After the writing is completed, the NIT data is held in the FIFO as shown in FIG.

  The NIT re-insertion unit 450 includes a memory unit 451 to which cable NIT data is sent from the control device 431 via the interface 432, as shown in a specific configuration example in FIG. The NIT replacement circuit 452 to which the TS is supplied stores the NIT data for the cable in the memory unit 451, and the NIT of the TS sent from the satellite system is converted into the NIT data for the cable by the NIT replacement circuit 452. Replace sequentially.

  The memory unit 451 has two FIFO memories 453 to which cable NIT data is sent from the control device 431 via the interface 432, and two pieces of cable NIT data are extracted from the FIFO memory 453 and stored. SRAMs 454A and 454B and an address counter 455 for generating the addresses of the SRAMs 454A and 454B. The memory unit 451 is controlled by the control device 431 to write and read data to and from the FIFO memory 453 via the interface 432, and is sent from the control device 431 via the interface 432. The cable NIT data is held in the FIFO memory 453, the cable NIT data is extracted from the FIFO memory 453, stored in the SRAM 454A or SRAM 454B, and the TS NIT is transferred from the satellite system to the NIT replacement circuit 452. Each time it is repeatedly sent, cable NIT data is sent from the SRAM 454A or SRAM 454B to the NIT replacement circuit 452.

  The NIT replacement circuit 452 includes a NIT packet detection circuit 456 to which the TS is supplied, a control unit 457 to which a detection output of the NIT packet detection circuit 456 is supplied, and a RAM switching circuit that is controlled by the control unit 457. 458 and a NIT switching circuit 459 that is switched and controlled by the detection output of the NIT packet detection circuit 456.

  The two SRAMs 454A and 454B of the memory unit 451 in the NIT reinsertion unit 450 are controlled by the control unit 457 of the NIT replacement circuit 452 to control data writing and reading each time the NIT is rewritten. Used alternately. That is, the controller 457 of the NIT replacement circuit 452 keeps the other SRAM 454B in an output-off state while outputting the data written in one SRAM 454A to the NIT replacement circuit 452, for example. The cable NIT data is written to the SRAM 454B via the FIFO memory 454A. When the writing of the latest cable NIT data to the SRAM 454B is completed, the output of the SRAM 454B is turned on so that the NIT data can be output to the NIT replacement circuit 452, and the output of the SRAM 454A is turned off. And wait until the next rewrite. The NIT data rewriting process for transferring data from the FIFO memory 453 to the SRAMs 454A and 454B is performed in real time with a clock synchronized with the TS.

  Here, the NIT data for the cable is written in the FIFO memory 453 via the interface 432 by the control device 431 in the order of NITa of the own network and NITo of the other network. Thereby, NITa of the own network and NITo of the other network are stored in the FIFO memory 453 as shown in FIG.

  When the control unit 457 receives the transfer start signal start from the control device 431, the NIT replacement circuit 452 transfers NIT data from the FIFO memory 453 to the SRAM 454A or the SRAM 454B. The transfer operation starts from NITa of the own network, and after writing all the data of NITa to the SRAM, the data of NITo of another network is written to a storage location different from the storage location of NITa of the SRAM. An example of writing NIT data to the SRAMs 454A and 454B is shown in FIG.

  In the NIT replacement circuit 452, NIT data transfer processing from the FIFO memory 453 to the SRAMs 454A and 454B is performed according to the procedure shown in the flowchart of FIG.

  That is, in the NIT replacement circuit 452, the control unit 457 controls the RAM switching circuit 458 for each TS packet and selects, for example, one SRAM 454A corresponding to the TS packet (step S11), It is determined whether or not the NIT packet detected by the NIT packet detection circuit 456 is a NITa packet of its own network (step S12), and if it is a NITa packet, the controller 457 is allowed to write to the memory unit 451. The address counter 455 is started (step S13), an address is generated by the address counter 455 (step S14), and the NITa data of its own network is transferred and written from the FIFO memory 453 to the other SRAM 454B (step S15).

  When the writing of the NITa data of the own network to the SRAM 454B is completed (step S15), or when the NIT packet detected by the NIT packet detection circuit 456 in the step S12 is not the NITa packet of the own network, the NIT It is determined whether or not the NIT packet detected by the packet detection circuit 456 is an NITo packet of another network (step S17). It waits for the detection of the NITa packet or the NITo packet of another network, and when it is a NITo packet, it gives the controller 457 permission to write to the memory unit 451 and addresses it. The counter 455 is started (step S18), the address is generated by the address counter 455 (step S19), and the NITo data of the other network is written into the SRAM 454B (step S20).

  When the writing of the NITo data of the other network to the SRAM 454B is finished (step S21), it is determined whether or not the processing for one TS packet is finished (step S22). When the processing for one TS packet is not finished Returning to step S11, when the processing for one TS packet is finished, the end is notified to the control device, the RAM switching circuit 458 is controlled to select the other SRAM 454B (step S23), and the FIFO memory 453 to the SRAM 454B. The transfer processing of NIT data to is terminated.

  In this way, the SRAM 454B storing the newly rewritten NIT data is put into a use state, and the SRAM 454A used so far is put into a standby state for the next NIT rewrite.

  Further, the NIT replacement circuit 452 performs transmission processing of NIT data from the FIFO memory 453 to the other SRAM 454B as described above, and transmits from the satellite system using the NIT data stored in one SRAM 454A. The replacement process for replacing the TS NIT with the cable NIT data is performed according to the procedure shown in the flowchart of FIG.

  That is, the NIT replacement circuit 452 determines whether or not the NIT packet detected by the NIT packet detection circuit 456 is the NITa packet of its own network (step S31). The address counter 455 is started (step S32), the address is generated by the address counter 455 (step S33), the NITa data of its own network is read from the SRAM 454A, and the NIT switching is performed via the RAM switching circuit 458. This is supplied to the circuit 457 (step S34).

  The NIT switching circuit 457 is switched from the error correction circuit 422 side to the RAM switching circuit 458 side during the period of the NIT packet by the detection output from the NIT packet detection circuit 456. As a result, the content of the TS NIT packet sent from the satellite system is replaced with the NITa data for the cable (step S35).

  When the reading of the NITa data of the own network from the SRAM 454A is completed (step S36), or when the NIT packet detected by the NIT packet detection circuit 456 in the step S31 is not the NITa packet of the own network, the NIT It is determined whether or not the NIT packet detected by the packet detection circuit 456 is a NITo packet of another network (step S37). The system waits for the detection of the NITa packet or the NITo packet of another network, and when it is a NITo packet, it issues a read permission from the memory unit 451 and an address counter. 455 is started (step S38), an address is generated by the address counter 455 (step S39), and the NITo data of the other network is read from the SRAM 454A (step S40).

  When the reading of the NITo data of the other network from the SRAM 454A is completed (step S41), the process returns to step S31, and the NITA packet detection circuit 456 detects the NITa packet of the next own network or the NITo packet of the other network. Wait.

  In the NIT conversion circuit 423 configured as described above, the satellite NIT data taken into the FIFO memory 442 by the NIT extraction unit 440 is sent to the control device 431 via the interface 432. The control device 431 restores the satellite NIT by software processing and generates an NIT suitable for cable transmission. Then, the NIT data converted for the cable is supplied from the control device 431 to the FIFO memory 453 of the NIT replacement unit 450 via the interface 432. In the NIT replacement unit 450 in this embodiment, data is written to the FIFO memory 453 in the order of NITa and NITo.

  The NIT conversion circuit 423 having such a configuration performs NIT processing according to the procedure shown in the flowchart of FIG.

  That is, first, the version number is changed (step S51), and the network ID is changed if necessary (step S52).

  Then, the processing loop of the TS from the satellite network is entered (step S53), and it is determined whether or not the stream (transponder in this case) from the satellite network is a transponder to be retransmitted to the cable network (step S54). If it is a transponder to be retransmitted, it is confirmed that it is a service list descriptor (Service_list_descriptor) (step S55), and it is determined whether or not it is a retransmission service (step S56).

  If it is not a retransmission service, the service ID and service type are deleted. That is, information (service ID) and service type of a program that does not provide a service in the stream that is being retransmitted are deleted (step S57).

  When it is a retransmission service, or after deleting the service ID and service type, check the descriptor length (step S58), replace the service list descriptor (Service_list_descriptor) length, and insert the stuffing descriptor (Stuff_descriptor) Then, the satellite delivery descriptor (Sattelite_delivery_descriptor) is replaced with the cable delivery descriptor (Cable_delivery_descriptor) (step S60).

  As described above, in the NIT rewriting process, for example, when a stream from the satellite network (here, transponder) is retransmitted to the cable network, at least the satellite delivery descriptor (Sattelite_delivery_descriptor) is replaced with the cable delivery descriptor (Cable_delivery_descriptor). Thus, the frequency information is matched. This is the minimum processing necessary to enable the receiving operation in the cable receiver. In addition, the information about the stream that is not retransmitted to the cable network (here, the transponder) and the information about the program that does not perform the service (service ID) in the stream that is being retransmitted are deleted to make up for the data that has been reduced by dummy data or the like. Furthermore, the NIT version number, the bit error index, and the like are matched with respect to the data length such as section length and descriptor length in the NIT as necessary.

  The dummy data needs to be negotiated so as not to cause a malfunction in the receiver. For example, a stuffing table ID, a stuffing descriptor tag, etc. are determined and determined as transmitter specifications, and when such a table ID or descriptor tag is transmitted, it is ignored by the receiver. What should I do?

  If the transponder is not to be retransmitted, the service list descriptor (Service_list_descriptor) and the satellite delivery descriptor (Sattelite_delivery_descriptor) are replaced with a stuffing descriptor (Stuff_descriptor) (step S61).

  Each time the process for the transponder to be retransmitted (steps S55 to S60) or the process for the transponder not to be retransmitted (step S61) is performed, the loop length of the TS is confirmed, the process returns to step S53, and the processes of steps S53 to S62 are performed. Is repeated over the loop length of the TS (step S62), after which the CRC 32 is replaced (step S63), and the NIT rewriting process is terminated.

  Similarly, network information related to other networks can be rewritten. For example, when services are provided by two satellites, if only one of the services is retransmitted in the cable network, the NITo section of the other network is converted to dummy data using the stuffing table ID. The NITa of both satellite networks is rewritten according to the service status in the cable network, and at the same time, the NITo is rewritten in conformity with the NITa.

  Next, a specific configuration example of the receiver 6 in the cable transmission system shown in FIG. 2 will be described with reference to FIG.

  In the receiver 6 having the configuration shown in FIG. 26, the reception tuner 62 of the cable front end unit 61 extracts a TS including a predetermined program from the mixed wave and outputs it to the QAM demodulation circuit 63. The QAM demodulating circuit 63 performs QAM demodulation on the input TS and outputs it to the error correction circuit 64. The error correction circuit 64 corrects the error information of the input TS and outputs it to the transport unit 65. The descrambler 66 of the transport unit 65 decodes (descrambles) the scramble applied to the TS using the descrambling information recorded on the IC card 60 issued by the satellite broadcasting service provider 1. Output to the multiplexer 67.

  The demultiplexer 67 extracts predetermined program information from the TS in which a plurality of program information is multiplexed and supplies the extracted program information to the MPEG decoding unit 68. The MPEG decoding unit 68 decompresses the input program information to generate a video signal and an audio signal, and outputs them to the television receiver 7.

  The host processor 69 controls the entire receiver 6 based on the viewer's channel selection operation, and records the received pay program information (program viewing information) on the IC card 60. Further, the host processor 69 reads the descrambling information recorded on the IC card 60 and supplies it to the descrambler 66. Further, the host processor 69 controls the communication unit 70 to notify the viewing information processing unit 14 of the satellite broadcast service provider 1 of the program viewing information recorded on the IC card 60 periodically via the public telephone line. .

  Next, information distribution processing by the distribution unit 34 in the cable television station 3 will be described with reference to the flowchart of FIG.

  In step S <b> 71, the CS antenna 31 receives a CS wave via the communication satellite 2 and outputs it to the distribution unit 34. The terrestrial antenna 32 receives the terrestrial wave and outputs it to the distribution unit 34. The BS antenna 33 receives a BS wave via a broadcasting satellite and outputs it to the distribution unit 34.

  In step S72, the signal distributor 41 divides the CS wave for each TS corresponding to one transponder, and outputs each to the modulation conversion devices 42-1 to 42-N. The terrestrial re-transmission device 44 converts the input terrestrial wave into RF and outputs it to the signal mixer 45. The satellite signal retransmitting device 44 converts the input BS wave into RF and outputs it to the signal mixer 45.

  In step S <b> 73, the QPSK demodulation circuit 421 of the modulation conversion device 42 performs QPSK demodulation on the input TS and outputs the result to the error correction circuit 422.

  In step S 74, the error correction circuit 422 performs error correction on the input signal and outputs it to the NIT conversion circuit 423.

  In step S75, the NIT conversion circuit 423 replaces the CS wave NIT with the cable television NIT and outputs the NIT for the cable television to the QAM modulation circuit 424.

  In step S76, the QAM modulation circuit 424 QAM modulates the input signal and outputs the result to the frequency conversion circuit 425.

  In step S 77, the frequency conversion circuit 425 converts the frequency of the input signal into a predetermined value that can be transmitted in the cable television network 4, and outputs the converted value to the signal mixer 45.

  In step S78, the signal mixer 45 mixes the QAM-modulated signals input from the modulation conversion devices 42-1 to 42-N, the terrestrial re-transmission device 43, and the satellite signal re-transmission device 44, respectively. To the amplifier 46.

  In step S <b> 79, the amplifier 46 amplifies the input mixed wave and distributes it to the receiver 6 via the cable television network 4.

  Next, the program reception process of the receiver 6 will be described with reference to the flowchart of FIG.

  In step S <b> 81, the reception tuner 62 of the cable front end unit 61 extracts TS including the program (program included in the CS wave) selected by the viewer from the mixed wave, and outputs it to the QAM demodulation circuit 63.

  In step S <b> 82, the QAM demodulation circuit 63 performs QAM demodulation on the input TS and outputs it to the error correction circuit 64.

  In step S <b> 83, the error correction circuit 64 corrects the error information of the input TS and outputs it to the transport unit 65.

  In step S84, the descrambler 66 of the transport unit 65 decodes the scramble applied to the TS using the descramble information recorded on the IC card 60 issued by the satellite broadcasting service provider 1, Output to the multiplexer 67.

  In step S85, the demultiplexer 67 demultiplexes the TS, extracts information on the program selected by the viewer, and supplies the extracted information to the MPEG decoding unit 68.

  In step S 86, the MPEG decoding unit 68 decompresses the input program information to generate a video signal and an audio signal, and outputs them to the television receiver 7. The television receiver 7 reproduces the input video signal and audio signal.

  In step S87, when the received program is a pay (pay per view) program, the host processor 69 records the information (program viewing information) on the IC card 60. The communication unit 70 periodically notifies the customer management unit 15 of the program viewing information recorded on the IC card 60 via the public telephone line and the viewing information processing unit 14.

    When the viewer selects a program transmitted by terrestrial or BS waves, the program information is not multiplexed and MPEG compression is not performed, so demultiplexing in step S85 and step S86 are performed. MPEG decompression is not performed.

  Next, an operation example of the receiver 6 of the receiving terminal device 5 that receives a signal transmitted from the cable television station 3 will be described with reference to a flowchart shown in FIG.

  The program number in PAT and PMT, and the service ID in NIT correspond to the channel number selected by each viewer. Further, the NIT includes information on the entire network, that is, all transponders, and the same table is transmitted in parallel by all transponders, whereas the PAT and PMT each have information on programs in the physical channel on which they are transmitted. The contents are different for each physical channel.

  For example, if the viewer selects the “M” channel, the host processor 69 controls the demultiplexer 67 so that the NIT is acquired by a fixed PID, and the service list attached to each TSID of the NIT. Search for “M” for the service ID in the descriptor (step S91).

  When the service ID “M” is present (step S92), the host processor 69 uses the “M” from the CATV delivery system descriptor combined before the service list descriptor including the service ID “M”. The frequency of the transponder transmitting the channel is recognized, and the reception frequency of the tuner 62 is controlled (step S93). As a result, the tuner 62 selects the digital broadcast signal from the modulation conversion device 42 transmitting the “M” channel.

  Then, the host processor 69 controls the demultiplexer 67 so that the PAT is acquired by a fixed PID, searches for “M” for the program number in the PAT, and recognizes the program number “M” in the PAT. Then, a program map PID associated with the program number “M” is obtained (step S94). Then, the host processor 69 controls the demultiplexer 67 so that the PMT is acquired by the program map PID, and the element for each stream type (video, audio, etc.) corresponding to the program number “M” in the PMT. A mental PID is recognized (step S95).

  Then, the host processor 69 controls the demultiplexer 67 so that TS packets having a PID that matches the elementary PID are separated (step S96). In this case, the host processor 69 separates the video data and audio data packets of the “M” channel and also separates the additional data packets of the “M” channel.

  Here, the host processor 69 supplies the limited reception information extracted from the additional data stream SDS to the IC card 60. In the IC card 60, whether or not viewing is possible is determined based on the limited reception information. If it is possible, the IC card 60 sends scramble key information to the host processor 69. This key information is set in the descrambler 66 by the host processor 69. As a result, the descrambler 66 de-scrambles the scrambled video data and audio data packets. Therefore, the video data stream and audio data stream obtained from the demultiplexer 67 are converted into scrambled data. It will be related.

  Then, the video data and audio data output from the demultiplexer 67 are decoded, and an “M” channel video signal and audio signal are obtained (step S97). In other words, the video data stream VDS output from the demultiplexer 67 is subjected to processing such as data expansion by the MPEG decoding unit 68 to generate a video signal SV, and this video signal is output. Also, the audio data stream output from the demultiplexer 67 is subjected to processing such as data expansion by the MPEG decoding unit 68 to generate an audio signal, and this audio signal is output. By supplying the video signal and the audio signal obtained by the MPEG decoding unit 68 to the television receiver 7, the “M” channel image can be displayed and the “M” channel sound can be output.

  In addition, when the service ID “M” is not found as a result of searching “M” for the service ID in the service list descriptor attached to each TSID in step S92, the host processor 69 cannot receive on the display unit (not shown). A message is displayed (step S98), and the receiving operation is terminated. Therefore, when the NIT conversion circuit 423 deletes information related to the TSID or service list descriptor information from the NIT as information on the service (program) to be restricted in view as described above, the receiver 6 Then, the service (program) cannot be received.

  In the flowchart of FIG. 29, it has been described that the NIT is acquired in step ST1 every time there is a channel selection of the “M” channel, and the search for “M” is performed using the NIT. The NIT may be acquired every time and stored in the internal memory of the host processor 69, and the search for “M” may be performed using the NIT. Incidentally, the change in the contents of the NIT is recognized by the version number.

  The receiver 6 of this embodiment shown in FIG. 26 can be realized by replacing the satellite front end 191 of the digital satellite broadcast receiver 182 shown in FIG. Manufacturing costs can be reduced.

  Also, according to the present embodiment, viewing information management such as billing calculation, which is the most costly for cable television, can be made common with the satellite broadcasting service provider, so that the cost can be reduced.

It is a conceptual diagram which shows the structure of the cable transmission system to which this invention is applied. It is a figure which shows each structure of the center station in the said cable transmission system, a cable television station, and a receiving terminal device. It is a figure which shows the frame structure of an MPEG2 transport packet and a DVB system. It is a figure which shows the packet structure of an MPEG2 transport packet. It is a figure which shows the packet structure of a PES packet. It is a figure which shows the table structure of a program association table (PAT). It is a figure which shows the table structure of a program map table (PMT). It is a figure which shows the table structure of a network information table (NIT). It is a figure which shows the structure of the satellite delivery system descriptor in NIT. It is a figure which shows the structure of the CATV delivery system descriptor in NIT. It is a figure which shows the structure of the service list descriptor in NIT. It is a block diagram which shows the structural example of the delivery part of the cable television station in the said cable transmission system. It is a figure explaining the linearly polarized wave of CS wave. It is a block diagram which shows the structural example of the modulation conversion apparatus in the said delivery part. It is a figure explaining a mixed wave. It is a block diagram which shows the structural example of the NIT conversion circuit in the said modulation conversion apparatus. It is a block diagram which shows the structural example of the NIT extraction part in the said NIT conversion circuit. It is a flowchart explaining the NIT extraction process by the said NIT extraction part. It is a figure which shows the example of writing to the FIFO memory in the said NIT extraction part. It is a block diagram which shows the structural example of the NIT replacement part in the said NIT conversion circuit. It is a figure which shows the example of writing to the FIFO memory in the said NIT replacement part. It is a figure which shows the example of writing to SRAM in the said NIT replacement part. It is a flowchart explaining the data transfer process from FIFO memory to SRAM in the said NIT replacement part. It is a flowchart explaining the NIT replacement process by the NIT replacement circuit in the NIT replacement unit. It is a flowchart explaining the NIT replacement process in the said NIT replacement part. It is a block diagram which shows the structural example of the receiver in the said cable transmission system. It is a flowchart explaining the information delivery process by the said delivery part. It is a flowchart explaining the program reception process by the said receiver. It is a flowchart explaining the channel selection process of the "M" channel by the said receiver. It is a block diagram which shows an example of a structure of the conventional cable television receiver. It is a conceptual diagram which shows the structure of a digital multichannel satellite broadcasting system. It is a block diagram which shows an example of a structure of the receiver in the said digital multichannel satellite broadcasting system.

Explanation of symbols

1 center station, 2 communication satellite, 3,3 ₁ to 3 _n cable TV station, 4 ₁ to 4 _n cable TV network, 5,5 ₁₁ to 5 _nm receiving terminal apparatus, 6 receiver, 7 television receiver 11 transmits Unit, 12 viewer management unit, 13 key management unit, 14 viewing information processing unit, 34 distribution unit, 35 customer management unit, 41 signal distributor, 42-1 to 42-N modulation conversion device, 45 signal mixer, 60 IC card, 61 cable front end section, 62 reception tuner, 63 QAM demodulation circuit, 64 error correction circuit, 65 transport section, 66 descrambler, 67 demultiplexer, 68 MPEG decoding section, 69 host processor, 71 communication section

Claims (6)

Receiving means for receiving a digital signal distributed from a center station modulated by a predetermined modulation method;
Demodulating means for demodulating the digital signal modulated by the predetermined modulation method received by the receiving means;
Transmission information replacement means for rewriting NIT contained in the signal demodulated by the demodulation means to NIT for cable television,
The transmission information replacing means deletes a signal that is not retransmitted from the digital signal distributed from the center station, and makes up the deleted signal with dummy data.   2. The information replacement device according to claim 1, wherein the rewriting of the NIT is performed by replacing a satellite delivery system descriptor in the NIT with a cable delivery descriptor.   2. The information replacement apparatus according to claim 1, wherein the transmission information replacement means performs error correction processing on the demodulated digital signal after demodulating the digital signal. Receiving a digital signal distributed from a center station modulated by a predetermined modulation method;
Demodulating the received digital signal modulated by the predetermined modulation method;
Rewriting the NIT contained in the demodulated signal to a NIT for cable television;
An information replacement method comprising: deleting a signal that is not retransmitted from the digital signal distributed from the center station, and filling the deleted signal with dummy data.   5. The information replacement method according to claim 4, wherein the rewriting of the NIT is performed by replacing a satellite delivery system descriptor in the NIT with a cable delivery descriptor. 5. The information replacement method according to claim 4, further comprising a step of performing error correction processing on the demodulated digital signal after demodulating the digital signal.

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