Transmission device, transmission system, and transmission method

Abstract

To switch a broadcast signal in proper switching unit with respect to an output transmission method in the time of abnormality detection.SOLUTION: Format conversion units 251, 252 convert one frame designated with reference time information included in a broadcast signal into a plurality of output transmission frames with a frame configuration according to an output transmission method, and add the reference time information included in the broadcast signal as individual time information to the plurality of output transmission frames. A read-out unit 281 specifies and selects a slot in another broadcast signal in the plurality of broadcast signals corresponding to a slot where an abnormality is detected on the basis of an offset amount to the slot where the abnormality is detected from the individual time information of the output transmission frame including the slot where the abnormality is detected when the abnormality is detected in any of the plurality of slots in the broadcast signal being selected. An output unit 282 outputs the selected slot in a prescribed output transmission method.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a transmission device, a transmission system, and a transmission method.

Background Art

[0002] Patent Document 1 discloses a broadcast signal switching device that inputs a plurality of broadcast signals in the MMT / TLV (MPEG Media Transport / Type Length Value) format, selects any one of the plurality of broadcast signals, and when an abnormality is detected in the selected broadcast signal, identifies a broadcast signal in which no abnormality has been detected or in which the number of detected abnormalities is small, and changes the selection to the identified broadcast signal.

[0003] According to such a broadcast system, an abnormality in the transmission path can be detected and the switching of the transmission path can be executed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the technique disclosed in Patent Document 1, the presence or absence of an abnormality is determined for each TLV packet. When there is an abnormality, abnormality information is generated for the TLV packet with the abnormality, and the broadcast signal is switched in units of TLV packets based on the abnormality information.

[0006] On the other hand, as described above, the selected broadcast signal is output from the broadcast signal switching device using a predetermined transmission method (such as packet communication in an IP network or a transmission signal modulated with a predetermined modulation method in CATV, etc.). In the above-described technology, the broadcast signal switching unit is set to the TLV packet unit without particularly considering the output transmission method. Therefore, the broadcast signal switching unit may not be appropriate for the output transmission method.

[0007] The present invention has been made in view of the above points, and aims to provide a transmission device, transmission system, and transmission method that switches the broadcast signal in an appropriate switching unit for the output transmission method when an anomaly is detected. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a transmission device that inputs a broadcast signal as multiple broadcast signals via multiple transmission paths and selects and outputs one of the multiple broadcast signals, comprising: an input means for inputting the multiple broadcast signals; a detection means for detecting abnormalities in the multiple broadcast signals; a format conversion means for performing format conversion of the multiple broadcast signals; a selection means for selecting one of the multiple broadcast signals after format conversion; and an output means for outputting the selected broadcast signal after format conversion using a predetermined output transmission method, wherein the format conversion means includes reference time information contained in the broadcast signal Time intervals divided by consecutive occurrence intervals This is considered as one frame, and the broadcast signal contained in this one frame is converted into multiple output transmission frames with a frame configuration corresponding to the output transmission method, Time values ​​included in the reference time information to each of the plurality of output transmission frames, The output transmission frame associated withThe individual time information is added, and the selection means (a) if no abnormality is detected in any of the multiple slots constituting the output transmission frame of the selected broadcast signal among the multiple broadcast signals, selects a slot of the selected broadcast signal; and (b) if an abnormality is detected in any of the multiple slots of the selected broadcast signal, the selection means identifies and selects a slot in another broadcast signal among the multiple broadcast signals that corresponds to the slot in which the abnormality was detected, based on the offset amount from the individual time information of the output transmission frame containing the slot in which the abnormality was detected to the slot in which the abnormality was detected, and the output means outputs the selected slot using the predetermined output transmission method. With this configuration, when an anomaly is detected, it becomes possible to switch the broadcast signal in appropriate switching units for the output transmission method.

[0009] Furthermore, the present invention is characterized in that the broadcast signal is an MMT / TLV broadcast signal, the reference time information included in the broadcast signal is NTP (Network Time Protocol) UTC (Coordinated Universal Time), the format conversion means sets the occurrence interval of the NTP UTC as one frame, converts the one frame into the plurality of output transmission frames, adds the UTC value to each of the plurality of output transmission frames, and each of the plurality of slots contains one or more TLV packets. With this configuration, when an anomaly is detected in an MMT / TLV broadcast signal, the broadcast signal can be switched in appropriate switching units for the output transmission method.

[0010] Furthermore, the present invention further comprises a transmission means that transmits a request to transmit the packet in which the abnormality has been detected in at least one of the plurality of transmission paths that is capable of bidirectional communication, and a receiving means that receives the requested packet in the bidirectional communication transmission path, wherein the detection means replaces the packet in which the abnormality has been detected in the selected broadcast signal with the received packet, and determines whether or not there is an abnormality in the selected broadcast signal after the replacement. With this configuration, the frequency of broadcast signal switching is reduced because alternative packets are acquired when an anomaly is detected.

[0011] Furthermore, the present invention comprises the above-mentioned transmission device as an upstream transmission device and a downstream transmission device that receives the broadcast signal output from the upstream transmission device, wherein the upstream transmission device transmits one of the plurality of broadcast signals to the downstream transmission device via the transmission path, and upon receiving the transmission request from the downstream transmission device, transmits the requested packet to the downstream transmission device. With this configuration, alternative packets are obtained from the upstream side when an anomaly is detected, resulting in a lower frequency of broadcast signal switching.

[0012] Furthermore, the present invention comprises a transmission device described in any one of the above-mentioned items and another transmission device that receives the broadcast signal output from the transmission device, wherein the other transmission device recovers the reference time information from the individual time information added to the output transmission frame if the reference time information included in the broadcast signal is not effectively received. This configuration reduces the frequency of loss of reference time information along the transmission path.

[0013] Furthermore, the present invention relates to a transmission method that inputs a certain broadcast signal as multiple broadcast signals via multiple transmission paths and selects and outputs one of the multiple broadcast signals, comprising: an input step of inputting the multiple broadcast signals; a detection step of detecting abnormalities in the multiple broadcast signals; a format conversion step of performing format conversion of the multiple broadcast signals; a selection step of selecting one of the multiple broadcast signals after format conversion; and an output step of outputting the selected broadcast signal after format conversion using a predetermined output transmission method, wherein the format conversion step includes reference time information contained in the broadcast signal Time intervals divided by consecutive occurrence intervals This is considered as one frame, and the broadcast signal contained in this one frame is converted into multiple output transmission frames with a frame configuration corresponding to the output transmission method, Time values ​​included in the reference time information to each of the plurality of output transmission frames, The output transmission frame associated with Individual time information is added, and in the selection step, (a) if no abnormality is detected in any of the multiple slots constituting the output transmission frame of the selected broadcast signal among the multiple broadcast signals, a slot of the selected broadcast signal is selected; (b) if an abnormality is detected in any of the multiple slots of the selected broadcast signal, a slot in another broadcast signal among the multiple broadcast signals corresponding to the slot in which the abnormality was detected is identified and selected based on the offset amount from the individual time information of the output transmission frame containing the slot in which the abnormality was detected to the slot in which the abnormality was detected; and in the output step, the selected slot is output using the predetermined output transmission method. With this configuration, when an anomaly is detected, it becomes possible to switch the broadcast signal in appropriate switching units for the output transmission method. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a transmission device, a transmission system, and a transmission method that switch broadcast signals in appropriate switching units for the output transmission method when an anomaly is detected.

[0015] The above or other objects, features, and advantages of the present invention will become more apparent from the following detailed description together with the accompanying drawings.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a diagram showing a configuration example of a transmission system 1 including a transmission device 20 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a detailed configuration example of the transmission device 20 shown in FIG. 1. [Figure 3] FIG. 3 is a diagram for explaining a frame structure of a broadcast signal in the MMT / TLV format. [Figure 4] FIG. 4 is a diagram for explaining a frame structure of a broadcast signal in an output transmission format. [Figure 5] FIG. 5 is a diagram for explaining the selection of slots in a broadcast signal after format conversion. [Figure 6] FIG. 6 is a flowchart showing an example of processing executed in the first embodiment. [Figure 7] FIG. 7 is a diagram showing a configuration example of a transmission system 1A including a transmission device 20A according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing a detailed configuration example of the transmission device 20A shown in FIG. 7.

Modes for Carrying Out the Invention

[0017] Next, embodiments of the present invention will be described.

[0018] (A) Description of the Configuration of the First Embodiment of the Present Invention FIG. 1 is a diagram showing a configuration example of a transmission system 1 including a transmission device 20 according to a first embodiment of the present invention. As shown in FIG. 1, the transmission system 1 includes an antenna 10, a receiving device 11, a transmitting device 12, a network 13, an antenna 14, a transmission device 20, a CATV (Cable Television) network 30, and subscriber homes 40-1 to 40-n (n>1).

[0019] Here, antenna 10 captures broadcast signals transmitted from a broadcasting satellite (not shown), converts them into electrical signals, and supplies them to receiving device 11. Receiving device 11 performs demodulation and error correction processing on the broadcast signals captured by antenna 10, and supplies the resulting video and audio data, etc., to transmitting device 12. Examples of broadcast signals include advanced BS broadcast signals and advanced CS broadcast signals. Of course, other broadcast signals may also be used.

[0020] The transmitting device 12 converts the video and audio data supplied from the receiving device 11 into packets compatible with the transmission method of the network 13 (IP network packet communication) and sends them to the network 13.

[0021] Network 13 is, for example, an IP (Internet Protocol) network such as the Internet, which is a global network composed of multiple servers interconnected, and transmits packets sent from the transmitting device 12 to the transmission device 20.

[0022] Antenna 14 captures broadcast signals transmitted from a broadcasting satellite (not shown), converts them into electrical signals, and supplies them to the transmission device 20. The broadcast signals transmitted from the broadcasting satellite are captured by antennas 10 and 14, which are installed at different locations.

[0023] The transmission device 20 receives a broadcast signal as multiple broadcast signals via multiple transmission paths and selects one of these multiple broadcast signals to output. In this case, the transmission device 20 receives broadcast signals supplied from the network 13 and the antenna 14, selects one to output, and switches to the other if an abnormality occurs in the selected broadcast signal.

[0024] The CATV network 30 is composed of, for example, optical cables or coaxial cables, and transmits broadcast signals output from the transmission device 20 to subscriber homes 40-1 to 40-n, respectively.

[0025] Subscriber homes 40-1 to 40-n are subscriber homes for cable television services, and are equipped with subscriber receiving equipment 41 (dedicated receivers, television sets, etc.) that receive broadcast signals transmitted via the CATV network 30. The broadcast signals transmitted via the CATV network 30 are carrier waves modulated with a predetermined modulation scheme, or packetized IP packets, etc.

[0026] Figure 2 shows a detailed configuration example of the transmission device 20 shown in Figure 1. As shown in Figure 2, the transmission device 20 includes receiving units 211, 212, TLV SYNC units 221, 222, TLV-NTP detection units 231, 232, anomaly detection units 241, 242, format conversion units 251, 252, buffers 261, 262, control unit 280, read unit 281, and output unit 282.

[0027] Here, the receiving unit 211 receives the electrical signal (RF signal) supplied from the antenna 14, performs demodulation processing, and supplies the obtained data to the TLV SYNC unit 221. The receiving unit 212 receives packets supplied from the network 13, extracts the data contained in the packets, and supplies the extracted data to the TLV SYNC unit 222.

[0028] The TLV SYNC units 221 and 222 extract TLV packets from the data streams supplied by the receiving units 211 and 212, respectively, and output them. The TLV SYNC units 221 and 222 may output single TLV packets or composite TLV packets.

[0029] The TLV-NTP detection units 231 and 232 detect NTP (hereinafter referred to as TLV-NTP) that are periodically included in the TLV packets supplied from the TLV SYNC units 221 and 222, obtain UTC as the time information included in the NTP, and supply it to the control unit 280.

[0030] The anomaly detection units 241 and 242 supply the anomalies detected by the receiving units 211 and 212 and the TLV SYNC units 221 and 222 to the control unit 280, respectively, and also detect anomalies in the TLV packets supplied from the TLV SYNC units 221 and 222, and notify the control unit 280 of the detected anomalies.

[0031] The format conversion units 251 and 252 each perform format conversion of multiple input broadcast signals. Here, the format conversion units 251 and 252 write the TLV packets (single TLV packets or composite TLV packets) supplied from the TLV SYNC units 221 and 222 to buffers 261 and 262, respectively, in a predetermined data format (frame structure).

[0032] Specifically, the format conversion units 251 and 252 each convert one frame, specified by the reference time information included in the broadcast signal (in this case, NTP UTC periodically included in the TLV packet), into multiple output transmission frames with a frame configuration corresponding to the output transmission method, and add the reference time information included in the broadcast signal to each of the multiple output transmission frames as individual time information. Each output transmission frame has multiple slots, and one slot is capable of accommodating one or more predetermined TLV packets.

[0033] Buffers 261 and 262 are configured, for example, as ring buffers, and TLV packets are written to them by format conversion units 251 and 252 in the data format described above.

[0034] The control unit 280 refers to the UTC supplied by the TLV-NTP detection units 231 and 232 to control the writing to the buffer by the format conversion units 251 and 252, and controls the read unit 281 based on the abnormality detected by the abnormality detection units 241 and 242 to select the buffer to be read.

[0035] The reading unit 281 selects one of several broadcast signals after format conversion. Here, the reading unit 281 selects either buffer 261 or buffer 262 for each slot according to the control unit 280, reads the slot from either buffer 261 or buffer 262, and supplies it to the output unit 282. The output unit 282 outputs the selected broadcast signal after format conversion using a predetermined output transmission method. Here, the output unit 282 transmits the slots selected sequentially by the reading unit 281 to subscriber homes 40-1 to 40-n via the CATV network 30 using the CATV network 30's transmission method (output transmission method).

[0036] Specifically, the readout unit 281 (a) selects a slot in the selected broadcast signal if no abnormality is detected in any of the multiple slots constituting the output transmission frame of the selected broadcast signal, and (b) if an abnormality is detected in any of the multiple slots of the selected broadcast signal, it identifies and selects a slot in another broadcast signal from the multiple broadcast signals that corresponds to the slot in which the abnormality was detected, based on the offset amount from the individual time information of the output transmission frame containing the slot in which the abnormality was detected to the slot in which the abnormality was detected (for example, the slot number within each output transmission frame). The output unit 282 then outputs the selected slot using a predetermined output transmission method.

[0037] Furthermore, by notifying the slot number within each output transmission frame in which an anomaly has been detected, it is possible to identify the slot in which an anomaly has been detected by counting the slots from the beginning of the output transmission frame, without buffering all slots within the output transmission frame.

[0038] (B) Description of the operation of the first embodiment of the present invention Next, the operation of the first embodiment of the present invention will be described. A broadcasting station (not shown) multiplexes compressed encoded video and audio containing information for realizing television broadcasting services, as well as data containing content for realizing content download services, based on a scheme called MMT / TLV. The multiplexed data is modulated, for example, using 16APSK (Amplitude Phase Shift Keying), and then transmitted as a broadcast signal. The broadcast signal transmitted from the broadcasting station is received by a broadcasting satellite (not shown) and transmitted toward the ground.

[0039] Antenna 10 captures broadcast signals (radio waves) transmitted from the broadcasting satellite, converts them into electrical signals, and supplies them to the receiving device 11. Antenna 14 also captures broadcast signals transmitted from the broadcasting satellite, converts them into electrical signals, and supplies them to the transmission device 20. Antennas 10 and 14 are located in different places. Therefore, for example, even if the reception conditions for antenna 10 are poor due to rainfall, antenna 14 may not be affected by the rainfall. As a result, the reception conditions of these two antennas 10 and 14 will differ, and the nature of any abnormalities that occur in the broadcast signal (presence or absence of abnormalities, degree of abnormality, etc.) will also differ.

[0040] The receiving device 11 performs, for example, 16APSK demodulation on the broadcast signal supplied from the antenna 10 and supplies the resulting TLV packets to the transmitting device 12. The transmitting device 12 converts the TLV packets supplied from the receiving device 11 into packets corresponding to the network 13 (for example, IP packets) and supplies them to the transmission device 20 via the network 13.

[0041] The transmission device 20 receives broadcast signals supplied via the antenna 14 and network 13, and selects and outputs broadcast signals with relatively few abnormalities from these broadcast signals.

[0042] More specifically, the receiving unit 211 demodulates the broadcast signal supplied from the antenna 14, extracts the multiplexed data, and supplies it to the TLV SYNC unit 221. If the level of the broadcast signal decreases or the broadcast signal is interrupted, the receiving unit 211 notifies the abnormality detection unit 241 of the abnormality. In addition, when demodulating the broadcast signal, the receiving unit 211 detects the MER (Modulation Error Ratio) and BER (Bit Error Rate), and for example, if the MER is less than 22 dB or the BER is 2.0 × 10⁻¹⁴ -4 If the value exceeds a certain limit, the abnormality detection unit 241 is notified of the abnormality.

[0043] The receiving unit 212 receives packets transmitted over the network 13, extracts the data contained in the packets, and supplies it to the TLV SYNC unit 222. If, for example, a received packet is missing, a link failure occurs, or an IP timeout occurs, the receiving unit 212 notifies the anomaly detection unit 242 of the anomaly.

[0044] The TLV SYNC units 221 and 222 extract and output TLV packets from the data supplied by the receiving units 211 and 212. Furthermore, if the TLV packets are out of sync, the TLV SYNC units 221 and 222 notify the anomaly detection units 241 and 242 of the anomaly, respectively.

[0045] Figure 3 illustrates the frame structure of a broadcast signal using the MMT / TLV method.

[0046] TLV packets with Type 02 contain an IP header and UDP (User Datagram Protocol) along with NTP, and the NTP contains UTC. As shown in Figure 3, TLV packets containing NTP are transmitted at approximately 33 msec intervals. TLV packets with Type 03 contain an IP header and UDP along with video data, etc.

[0047] As mentioned above, antennas 10 and 14 shown in Figure 1 are located in different places, and the broadcast signals are transmitted via different transmission paths. Therefore, the TLV packets output from TLV SYNC units 221 and 222 have a time delay.

[0048] Then, the TLV-NTP detection units 231 and 232 detect NTP from the TLV packets output from the TLV SYNC units 221 and 222 and notify the control unit 280.

[0049] The anomaly detection units 241 and 242 detect anomalies (data corruption, packet loss, data loss, decoding failure, etc.) in TLV packets output from the TLV SYNC units 221 and 222, respectively, and identify the TLV packets for which anomalies were detected by the anomaly detection units 241 and 242, the TLV packets for which anomalies were notified by the receiving units 211 and 212, and the TLV packets for which anomalies were notified by the TLV SYNC units 221 and 222, respectively.

[0050] Data corruption in TLV packets is detected, for example, by the CRC (Cyclic Redundancy Check) value. Data loss is detected, for example, based on the TLV Length or Payload Length within MMTP. Packet loss is detected as packet discontinuity, for example, based on the packet sequence number, which is an MMTP continuity index for each packet ID as described in ARIB TR-B39 Chapter 12, 12.4, 12.5.

[0051] The format conversion units 251 and 252 use the TLV-NTP detected by the TLV-NTP detection units 231 and 232 to write the TLV packets output by the TLV SYNC units 221 and 222 to buffers 261 and 262, respectively, so that they have a frame structure corresponding to the output transmission method of the output unit 282.

[0052] Figure 4 illustrates the frame structure of a broadcast signal using the output transmission method. In the output transmission method frame structure shown in Figure 4, a TLV packet containing an NTP (the same as the one received) is inserted periodically at 33ms. Multiple output transmission frames (e.g., 10) are set between one TLV packet containing an NTP and the next, and each output transmission frame contains multiple slots (120 in this case). Furthermore, a field with an NTP value is set at the beginning of each output transmission frame. This NTP value has the same UTC value as the NTP contained in the TLV packet containing the NTP. In other words, multiple output transmission frames up to the next TLV packet containing an NTP have the same NTP value as the UTC value in the TLV packet containing the NTP immediately preceding those multiple output transmission frames.

[0053] In output transmission systems, the number of slots and slot size in a single output transmission frame are defined by the bitrate of the broadcast signal and the transmission capacity of the modulation scheme used for output (e.g., 16APSK, 32APSK). After formatting the frame structure to match the specifications of such an output transmission system, the broadcast signal is selected in slot units. This allows for immediate transmission processing of the broadcast signal (carrier modulation, packetization, etc.) after slot selection.

[0054] Returning to Figure 2, the control unit 280 queries the format conversion unit (format conversion unit 251 or format conversion unit 252) corresponding to the transmission path of the TLV packet in which the abnormality was detected, for the offset amount from the NTP at the beginning of the output transmission frame of the slot containing the TLV packet in which the abnormality was detected. Once the offset amount is identified, the control unit 280 notifies the read unit 281 of that offset amount.

[0055] Then, the reading unit 281 reads a slot (specifically, the data in the slot) from either buffer 261 or buffer 262 in accordance with the control unit 280 and supplies it to the output unit 282.

[0056] Figure 5 illustrates the selection of slots in a broadcast signal after format conversion. Specifically, as shown in Figure 5, for example, if no abnormality is detected in the current output transmission frame of the currently selected transmission path (transmission path #1 in Figure 5), the readout unit 281 reads the slots of that output transmission frame in order. If an abnormality is detected in the current output transmission frame of the currently selected transmission path, the readout unit 281 identifies the slot where the abnormality was detected based on the notified offset amount (in this case, the slot number), and for that slot, reads the corresponding slot in the current output transmission frame of another transmission path (transmission path #2 in Figure 5).

[0057] If all output transmission frame slots in the transmission path are abnormal, the system will select and read a slot that has the least impact during playback. "Little impact during playback" means that there is minimal disturbance to the played-back video and audio. For example, if the UDP checksum of the TLV is abnormal, an MMT packet error occurs, or the sequence number within the MMTP is abnormal, the system will select the slot with the least impact in that order.

[0058] The slots read by the reading unit 281 are supplied to the output unit 282. The output unit 282 transmits the slots supplied from the reading unit 281 as a broadcast signal to subscriber homes 40-1 to 40-n via the CATV network 30 using a predetermined output transmission method. This broadcast signal is received by subscriber receiving equipment 41 (for example, an STB (Set Top Box) or a television receiver) located in subscriber homes 40-1 to 40-n, and the video and audio contained in the broadcast signal are reproduced by the subscriber receiving equipment 41 or the television receiver connected to the subscriber receiving equipment 41.

[0059] As described above, according to the embodiment of the present invention, the broadcast signal is switched in units of slots in the frame structure of the output transmission method, so the broadcast signal can be switched appropriately without interruption.

[0060] Furthermore, according to the above embodiment, for multiple transmission paths, the broadcast signal data is buffered in the frame structure of the output transmission method, and the broadcast signal can be selected and output immediately on a slot-by-slot basis. Compared to the case where the broadcast signal is selected on a TLV packet basis and then converted to the frame structure of the output transmission method, the processing time for selecting the broadcast signal for each TLV packet is eliminated, thus reducing the delay in the transmission device.

[0061] Next, with reference to Figure 6, an example of the signal processing flow in the first embodiment will be described. Figure 6 is a flowchart showing an example of the processing performed in the first embodiment. When a broadcast signal is input to the transmission device 20 shown in Figure 2, the following steps are performed as shown in Figure 6.

[0062] In step S1, the receiving units 211 and 212 perform the process of receiving the broadcast signal. For example, in the example in Figure 2, the receiving unit 211 receives the broadcast signal supplied from the antenna 14, and the receiving unit 212 receives the broadcast signal supplied from the network 13. The receiving unit 211 notifies the anomaly detection unit 241 if it detects an anomaly such as a drop in the broadcast signal level, low MER, or high BER. The receiving unit 212 also notifies the anomaly detection unit 242 if it detects an anomaly such as packet loss, link failure, or IP timeout.

[0063] In step S2, the TLV SYNC units 221 and 222 extract TLV packets contained in the broadcast signal, and the TLV-NTP detection units 231 and 232 detect TLV packets containing NTP. The NTP detected in this way is supplied to the control unit 280. At this time, if the TLV packets are out of sync, the TLV SYNC units 221 and 222 notify the anomaly detection units 241 and 242 of the anomaly.

[0064] In step S3, the anomaly detection units 241 and 242 perform the process of detecting anomalies in the TLV packets as described above, and notify the control unit 280 of the detected anomaly (identification information of the anomalyed packet, type of anomaly, etc.).

[0065] In step S4, the format conversion units 251 and 252 buffer the extracted TLV packets according to the time difference of the broadcast signals and write them to buffers 261 and 262 in the format-converted frame configuration.

[0066] More specifically, for example, the control unit 280 determines the time difference τ between two broadcast signals from the timing difference in the detection of TLV packets containing NTP detected by the TLV-NTP detection units 231 and 232. Then, the control unit 280 buffers a number of TLV packets corresponding to the preceding broadcast signal in the format conversion unit 251 or format conversion unit 252. Note that the time difference τ of broadcast signals passing through network 13 changes moment by moment depending on the traffic conditions of network 13, so it is desirable to set the number of packets to be buffered with a certain margin.

[0067] In step S5, the control unit 280 controls the read unit 281 to select and read from the slots stored in buffers 261 and 262 that will have less impact from the abnormality. More specifically, if at least one of the slots is free of abnormalities, the control unit 280 selects and reads the slot that is free of abnormalities. If both slots are abnormal, the control unit 280 selects and reads the slot that will have less impact during playback.

[0068] Here, the control unit 280 indicates the data to be read. More specifically, information to identify which of the two buffers 261 and 262 the reading unit 281 is reading from (for example, "Transmission Path #1" for buffer 261, "Transmission Path #2" for buffer 262, etc.) is displayed on a display unit that is not shown.

[0069] In step S6, the output unit 282 transmits the TLV packets containing NTP and the slots within the output transmission frame (such as the TLV packets contained in the slots), which have been read sequentially by the read unit 281, using a predetermined output transmission method.

[0070] As explained above, the broadcast signal is output while being switched by the process shown in Figure 6.

[0071] (C) Description of the configuration of the second embodiment of the present invention

[0072] Next, a second embodiment of the present invention will be described with reference to Figure 7. In Figure 7, parts corresponding to those in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0073] Figure 7 shows an example configuration of a transmission system 1A including a transmission device 20A according to the first embodiment of the present invention.

[0074] In this transmission system 1A, an antenna 15 similar to antenna 14 is installed at a different location from antenna 14. Antenna 15 captures broadcast signals transmitted from a broadcasting satellite (not shown), converts them into electrical signals, and supplies them to the transmission device 20.

[0075] In the second embodiment, the transmission device 20A receives broadcast signals supplied from antenna 14 and antenna 15, selects one of them to output, and switches to the other if an abnormality occurs in the selected broadcast signal.

[0076] In the second embodiment, the transmitter 12A has the same functions as the transmitter 12, but does not transmit packets corresponding to broadcast signals at all times, and only transmits packets for which a transmission request has been made.

[0077] Figure 8 shows a detailed configuration example of the transmission device 20A shown in Figure 7. In Figure 8, parts corresponding to those in Figure 2 are denoted by the same reference numerals and their descriptions are omitted. In the second embodiment, the transmission device 20A includes a receiving unit 211A similar to the receiving unit 211 instead of the receiving unit 212. The receiving unit 211A receives an electrical signal (RF signal) supplied from the antenna 15, performs demodulation processing, and supplies the obtained data to the TLV SYNC unit 222.

[0078] Furthermore, the transmission device 20A includes a transmission request unit 310 and a reception unit 320. The transmission request unit 310 transmits a transmission request for the packet in which an anomaly has been detected on at least one of the multiple transmission paths that is capable of bidirectional communication (in this case, a network 13 such as an IP network). The reception unit 320 receives the requested packet on that bidirectional communication-capable transmission path. In the second embodiment, the anomaly detection units 241 and 242 replace the packet in which an anomaly has been detected in the selected broadcast signal with the packet received by the reception unit 320, and determine whether or not there is an anomaly in the selected broadcast signal after the replacement. In other words, if there is still an anomaly after the packet replacement with the replacement packet, the anomaly is detected in the same way as in the first embodiment.

[0079] (D) Description of the operation of the second embodiment of the present invention

[0080] In the second embodiment, when an anomaly is detected, the anomaly detection units 241 and 242 attempt to recover the TLV packet in which an anomaly was detected (replace it with a normal TLV packet). Specifically, when the anomaly detection units 241 and 242 notify the control unit 280 of a TLV packet in which an anomaly has been detected, the control unit 280 causes the transmission request unit 310 to send a transmission request for that TLV packet to the transmission device 12A.

[0081] When the transmitting device 12A receives the transmission request, it transmits the TLV packet specified by the transmission request. In this case, the packet to be transmitted may be specified by the slot number mentioned above, and the packet contained in the slot with that slot number may be transmitted from the transmitting device 12A.

[0082] When the receiving unit 320 receives the TLV packet, the control unit 280 supplies the TLV packet to the abnormality detection unit 241 or 242 that detected the abnormality, and the abnormality detection unit 241 or 242 replaces the TLV packet in which it detected an abnormality with the TLV packet. Subsequently, the abnormality detection unit 241 or 242 determines whether there is an abnormality in the replaced TLV packet and operates in the same manner as in the first embodiment according to the determination result.

[0083] (E) Description of modified embodiments The embodiments described above are merely examples, and it goes without saying that the present invention is not limited to the cases described above. For example, in the embodiments described above, the transmission devices 20 and 20A are configured to receive two broadcast signals, but they may also receive three or more broadcast signals and select a slot that is less affected by abnormalities to output.

[0084] Furthermore, in the first embodiment described above, antenna 14 is connected to the transmission device 20, and antenna 10 is connected to the transmission device 20 via the receiving device 11, the transmitting device 12, and the network 13. However, other connection configurations are also possible. For example, both antenna 10 and antenna 14 may be connected to the transmission device 20, or both antenna 10 and antenna 14 may be connected to the transmission device 20 via the receiving device, the transmitting device, and the network.

[0085] Furthermore, in each of the above embodiments, the transmission devices 20 and 20A supply broadcast signals to subscriber homes 40-1 to 40-n via a transmission line such as a CATV network 30. However, the transmission devices 20 and 20A may also be placed in the same subscriber homes 40-1 to 40-n, and the transmission devices 20 and 20A may directly supply broadcast signals to the subscriber receiving devices 41 in the subscriber homes 40-1 to 40-n.

[0086] Furthermore, in each of the above embodiments, the broadcast signal is an MMT / TLV broadcast signal, the reference time information included in the broadcast signal is NTP UTC, the format conversion units 251 and 252 use the occurrence interval of NTP UTC as one frame, convert the one frame into multiple output transmission frames, and attach the UTC value as individual time information to each of the multiple output transmission frames, with each of the multiple slots containing one or more TLV packets. Alternatively, the broadcast signal may be an MPEG-2 TS broadcast signal, the reference time information included in the broadcast signal may be TOT (Time Offset Table) or PCR (Program Clock Reference) time information, the format conversion units 251 and 252 use a fixed period defined by TOT or PCR as one frame, convert the one frame into multiple output transmission frames, and attach the value indicated by RTP or PCR as individual time information to each of the multiple output transmission frames. Furthermore, in the above embodiment, the broadcast signal is transmitted over a wide area via satellite broadcasting, but instead, it may be transmitted over a wide area from a ground-based transmission station (relay station), for example, as in the terrestrial digital television broadcasting system. In that case, antennas 10, 14, receiving device 11, receiving unit 211, etc., that are compatible with such broadcast signal transmission methods will be used.

[0087] Furthermore, in the above embodiment, 16APSK was used as an example of a modulation scheme for satellite broadcasting, but other methods such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 8PSK, or 32APSK may also be used, or other methods including OFDM (Orthogonal Frequency Division Multiplexing) may be used.

[0088] Furthermore, in the above embodiment, the input of the broadcast signal to the transmission devices 20 and 20A may be performed by optical communication.

[0089] Furthermore, in the above embodiment, the broadcast signal output from the transmission devices 20, 20A (upstream transmission devices) is supplied to the subscriber receiving device 41, but instead, it may be supplied to other transmission devices 20, 20A (downstream transmission devices) (i.e., used as input to other transmission devices 20, 20A).

[0090] In that case, the downstream transmission devices 20, 20A, which are supplied with broadcast signals from the upstream transmission devices 20, 20A, may receive the broadcast signals output from the upstream transmission devices 20, 20A, and if the reference time information contained in the broadcast signal is not received effectively (for example, in the case of loss or corruption of TLV packets including NTP), they may reconstruct the reference time information from the individual time information attached to the output transmission frame and output a broadcast signal containing the reconstructed reference time information.

[0091] Furthermore, in that case, similar to the second embodiment described above, the downstream transmission devices 20, 20A may send a transmission request for the packet in which an anomaly has been detected in at least one of the multiple transmission paths that is capable of bidirectional communication (here, network 13 such as an IP network) to the upstream transmission devices 20, 20A. Upon receiving the transmission request, the upstream transmission devices 20, 20A send the requested packet to the downstream transmission devices 20, 20A. The downstream transmission devices 20, 20A receive the requested packet in the bidirectional communication-capable transmission path, replace the packet in which an anomaly has been detected in the selected broadcast signal with the received packet, and then determine whether or not there is an anomaly in the selected broadcast signal after the replacement. In this case, the packet to be transmitted may be specified by the slot number described above, and the packet contained in the slot of that slot number may be retransmitted. [Industrial applicability]

[0092] The present invention can be applied, for example, to a transmission device for broadcast signals via satellite broadcasting. [Explanation of Symbols]

[0093] 1.1A transmission system 10, 14, 15 Antennas 11 Receiving device 12,12A Transmitter 20,20A transmission device 30 CATV network 40-1~40-n Subscriber's home 41 Subscriber receiving device 211, 211A, 212 Receiving unit (example of input means) 221,222 TLV SYNC section 231,232 TLV-NTP detection unit 241,242 Anomaly detection unit (example of detection means) 251,252 Format conversion unit (example of format conversion means) 261,262 buffers 280 Control Unit 281 Reading unit (an example of a selection method) 282 Output section (an example of an output means) 310 Transmission Request Unit (An example of a transmission request means) 320 Receiving unit (an example of a receiving means)

Claims

1. In a transmission device that inputs a certain broadcast signal as multiple broadcast signals via multiple transmission paths and selects and outputs one of the multiple broadcast signals, The input means for inputting the aforementioned multiple broadcast signals, A detection means for detecting abnormalities in the aforementioned multiple broadcast signals, A format conversion means for performing the format conversion of the aforementioned multiple broadcast signals, A selection means for selecting one of the multiple broadcast signals after the format conversion, The system includes output means for outputting the selected broadcast signal after format conversion using a predetermined output transmission method, The format conversion means defines a time interval divided by the consecutive occurrence intervals of the reference time information contained in the broadcast signal as one frame, converts the broadcast signal contained in one frame into a plurality of output transmission frames with a frame configuration according to the output transmission method, and adds the time value contained in the reference time information to each of the plurality of output transmission frames as individual time information associated with that output transmission frame. The selection means (a) selects a slot in the selected broadcast signal if no abnormality is detected in any of the multiple slots constituting the output transmission frame in the selected broadcast signal, and (b) identifies and selects a slot in another broadcast signal from the multiple broadcast signals that corresponds to the slot in which the abnormality was detected, based on the offset amount from the individual time information of the output transmission frame containing the slot in which the abnormality was detected to the slot in which the abnormality was detected. The output means outputs the selected slot using the predetermined output transmission method. A transmission device characterized by the following.

2. The aforementioned broadcast signal is an MMT / TLV (MPEG Media Transport / Type Length Value) broadcast signal, The reference time information included in the aforementioned broadcast signal is UTC (Coordinated Universal Time) of NTP (Network Time Protocol). The format conversion means sets the interval between occurrences of UTC in the NTP as one frame, converts the one frame into the plurality of output transmission frames, and adds the UTC value to each of the plurality of output transmission frames. Each of the aforementioned slots contains one or more TLV packets. The transmission device according to claim 1, characterized by the following:

3. A transmission request means that transmits a transmission request for the packet in which the abnormality has been detected, in a transmission path that is capable of bidirectional communication, which is at least one of the plurality of transmission paths, The transmission path, which is capable of bidirectional communication, further comprises receiving means for receiving the requested packet, The detection means replaces the packet in which the abnormality was detected in the selected broadcast signal with the received packet, and after the replacement, determines whether or not there is an abnormality in the selected broadcast signal. The transmission device according to claim 1, characterized by the following:

4. A transmission device according to claim 3 as a downstream transmission device, The system comprises an upstream transmission device that outputs the broadcast signal to the downstream transmission device, The upstream transmission device transmits one of the plurality of broadcast signals to the downstream transmission device via the transmission path, and upon receiving the transmission request from the downstream transmission device, transmits the requested packet to the downstream transmission device. A transmission system characterized by the following.

5. A transmission device according to any one of claims 1 to 3, The system comprises a downstream transmission device that receives the broadcast signal output from the aforementioned transmission device, The downstream transmission device, if the reference time information included in the broadcast signal is not effectively received, shall reconstruct the reference time information from the individual time information added to the output transmission frame. A transmission system characterized by the following.

6. In a transmission method that inputs a certain broadcast signal as multiple broadcast signals via multiple transmission paths and selects and outputs one of the multiple broadcast signals, An input step for inputting the aforementioned multiple broadcast signals, A detection step for detecting abnormalities in the multiple broadcast signals, A format conversion step that performs the format conversion of the multiple broadcast signals, A selection step of selecting one of the multiple broadcast signals after the format conversion, The system includes an output step of outputting the selected broadcast signal after format conversion using a predetermined output transmission method, The format conversion step involves defining a time interval divided by the consecutive occurrence intervals of the reference time information contained in the broadcast signal as one frame, converting the broadcast signal contained in one frame into a plurality of output transmission frames with a frame configuration according to the output transmission method, and adding the time value contained in the reference time information to each of the plurality of output transmission frames as individual time information associated with that output transmission frame. In the selection step, (a) if no abnormality is detected in any of the multiple slots constituting the output transmission frame of the selected broadcast signal among the multiple broadcast signals, a slot of the selected broadcast signal is selected; (b) if an abnormality is detected in any of the multiple slots of the selected broadcast signal, a slot in another broadcast signal among the multiple broadcast signals corresponding to the slot where the abnormality was detected is identified and selected based on the offset amount from the individual time information of the output transmission frame containing the slot where the abnormality was detected to the slot where the abnormality was detected. In the output step, the selected slot is output using the predetermined output transmission method. A transmission method characterized by the following.

7. A transmission request step in which a transmission request for the packet in which the abnormality has been detected is sent from the downstream transmission device to the upstream transmission device in a transmission path capable of bidirectional communication, which is at least one of the plurality of transmission paths, When the upstream transmission device receives the transmission request, it performs a packet transmission step of transmitting the requested packet from the upstream transmission device to the downstream transmission device via the bidirectional communication-capable transmission path. The transmission path, which is capable of bidirectional communication, further comprises a packet receiving step in which the downstream transmission device receives the packet that has been requested to be transmitted, In the detection step, the packet in which the abnormality was detected in the selected broadcast signal is replaced with the packet received by the downstream transmission device, and after the replacement, it is determined whether or not there is an abnormality in the selected broadcast signal. The transmission method according to claim 6, characterized by the following:

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