JP2008244704A - Digital broadcast signal retransmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital broadcast signal retransmitter which transfers a digital broadcast signal using an IP (Internet Protocol) circuit, and smoothly retransmit the broadcast signal. <P>SOLUTION: A receiving device 1 receives the digital broadcast signal, and transfers MPEG2-TS (MPEG-Transport Stream) packets to an OFDM (Orthogonal Frequency Division Multiplex) modulator 2 through the IP circuit. The device 2 is composed by comprising a TS buffer circuit 200 which stores the TS packets, a transfer rate calculating means 201 which calculates a transfer rate based on PCR (Program Clock Reference) of the TS packets, a frequency generation circuit 202 which generates a reproduction rate clock frequency of the TS buffer circuit 200 based on the transfer rate in order to retransmit the transferred broadcast signal. The device 2 is provided with a PCR extraction circuit 204 which extracts the PCR; an STC (System Time Clock) counter 205; a 27 MHz oscillator 206; and an error detecting circuit 207 which detects an error of the reproduction rate clock frequency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a digital broadcast signal retransmission apparatus, and more particularly, to acquire data representing a digital broadcast signal acquired via an IP line and retransmit the acquired data as a digital broadcast signal again. Relates to the device.

  Television broadcasting in Japan is shifted from conventional terrestrial analog television broadcasting to terrestrial digital television broadcasting. The terrestrial digital television broadcasting system broadcast in Japan is called the ISDB-T (Integrated Services Digital Broadcasting for Terrestrial) system, and the OFDM (Orthogonal Frequency Division Multiplexing) system is used as the modulation system. Is done. In this digital terrestrial television broadcast, transmission data is divided into 13 segments and broadcast. In general, a television set fixed in a home or the like receives these 13 segments at a time, and a mobile terminal device (such as a mobile phone) carried by a user has only one segment out of these 13 segments ( The so-called “one segment” is received.

  By the way, in such terrestrial digital television broadcasting, it is expected that there is a difficult viewing area as in the case of conventional terrestrial analog television broadcasting. Therefore, various proposals have conventionally been made on how to eliminate such a difficult viewing area, in other words, how to transmit a terrestrial digital television broadcast signal to the difficult viewing area.

  As one of them, in order to provide terrestrial digital television broadcasting to a wide area, as with conventional terrestrial analog television broadcasting, terrestrial digital television broadcasting signals transmitted from a transmitting station are transmitted by a plurality of relay stations. Relaying is being considered and is actually taking place. However, when relaying a terrestrial digital television broadcast signal, each relay station needs to synchronize with the reference clock frequency (27 MHz) of the broadcast station. That is, as described above, in the terrestrial digital television broadcasting, the OFDM method is adopted as the modulation method, and therefore it is necessary to synchronize the sampling clock frequency for OFDM with the clock frequency of the terrestrial digital television broadcast signal to be (re) transmitted. There is. In this case, if the sampling clock frequency for OFDM and the reference clock frequency of the terrestrial digital television broadcast signal are shifted, a shift occurs in the clock frequency of the (re) transmitted broadcast signal, and the receiving device (TV or mobile terminal device) Etc.) may be difficult.

On the other hand, for example, an OFDM transmitter as shown in Patent Document 1 below is known. This conventional OFDM transmitter is applied to a relay device of a digital terrestrial television broadcasting system, and extracts a clock signal from a GPS signal received by a GPS antenna provided in the relay device using a rubidium transmitter and broadcasts it. A clock frequency monitoring device that generates a reference clock signal synchronized with a station and monitors a clock frequency difference using the generated reference clock signal is provided. That is, the clock frequency monitoring device in this conventional OFDM transmitter compares the modulated clock signal generated by the OFDM modulator with the generated reference clock signal and monitors whether the clock frequency difference is within an allowable range. It has become.
JP 2006-279583 A

  By the way, in the above conventional OFDM transmitter, since a reference clock signal can be generated from a GPS signal using a rubidium transmitter, for example, when a terrestrial digital television broadcast signal is relayed between a plurality of relay devices, It is possible to make the reference clock signal in each relay device completely coincide. Thereby, it is possible to completely eliminate the deviation between the sampling frequency for OFDM and the reference clock frequency of the terrestrial digital television broadcast signal. However, providing each relay device with a GPS antenna and a rubidium transmitter imposes a very large cost burden. Further, since the GPS signal is used, an installation place where each relay device can satisfactorily receive the GPS signal from the satellite is required. For this reason, it is eager to reduce the facility cost for transmitting high-quality digital terrestrial television and to eliminate difficult viewing areas.

  In this regard, data representing a terrestrial digital television broadcast signal is transferred to a difficult viewing area using an IP (Internet Protocol) line, and the transferred terrestrial digital television broadcast signal is transmitted in the difficult viewing area by OFDM. Retransmission is being considered. Thereby, since the relay station is not required by using the existing IP line, the equipment cost for broadcasting high-quality digital terrestrial television can be reduced. However, when a digital terrestrial television broadcast signal transmitted from a broadcasting station is transferred via an IP line, the broadcast signal is transferred in the form of an IP packet. There is no reference clock that can be used by receiving a television broadcast signal.

  Therefore, in the case of retransmitting digital terrestrial television broadcasting using an IP line in this way, the terrestrial digital television to be retransmitted with the reference clock frequency of the transmitted (or received) terrestrial digital television broadcast signal. It becomes difficult to match the reference clock frequency of the John broadcast signal. As a result, re-transmission processing takes time, for example, data representing a terrestrial digital television broadcast signal transferred via an IP line may be delayed before being re-transmitted, and may not be re-transmitted smoothly. There is. Therefore, it is desired that the terrestrial digital television broadcast signal can be smoothly retransmitted.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to transfer data representing a digital broadcast signal using an IP line and smoothly re-transfer the transferred data as a digital broadcast signal. An object of the present invention is to provide a digital broadcast signal retransmission apparatus capable of transmitting.

  A feature of the present invention is that a transport stream formed in a predetermined block unit is acquired via an IP line using a transport packet representing a digital broadcast signal, and the acquired transport stream is subjected to orthogonal frequency division multiplexing modulation. A digital broadcast signal retransmitting device comprising orthogonal frequency division multiplex modulation means for transmitting again as a digital broadcast signal, the buffer means for temporarily storing the acquired transport stream of the predetermined block unit, and the acquisition Specific information extraction means for extracting specific information to be inserted into the transport stream at a predetermined interval, and using the extracted specific information, a reproduction rate clock frequency of the temporarily stored transport stream is determined. Reproduction rate clock frequency generation means for generating and the extraction The using specific information is to have a reproduction rate clock frequency correction means for correcting the playback rate clock frequency that is generated.

  In this case, the transport stream temporarily stored in the buffer means is sent to the TS_FIFO that is stored and output in the input order of the transport stream, and the reproduction rate clock frequency generating means is stored in the TS_FIFO. It is preferable to generate a reproduction rate clock frequency for sequentially transmitting the transport streams.

  In this case, the specific information may be, for example, a program clock reference (PCR) inserted to adjust a buffer amount when the transport stream is temporarily stored.

  In this case, the reproduction rate clock frequency generation means may generate the reproduction rate clock based on the number of bytes existing between program clock references (PCR) included in the transport stream.

  According to these, it is possible to transfer a transport stream of a digital broadcast signal as a predetermined block unit via an IP line (for example, an Internet line) and temporarily store the transferred transport stream in a buffer means. it can. Then, using the specific information included in the stored transport stream, more specifically, the program clock reference (PCR), it is possible to generate the reproduction rate clock frequency for sending the transport stream stored in the buffer means. . Thereby, the transport stream can be smoothly transmitted from the buffer means, and the buffer amount of the transport stream stored in the buffer means can be appropriately maintained. Therefore, the digital broadcast signal can be smoothly retransmitted.

  Further, by providing TS_FIFO, the buffer amount of the buffer means can be more appropriately maintained. That is, the reproduction rate clock frequency generation means generates the reproduction rate clock frequency of the transport stream transmitted from the TS_FIFO, so that the transport stream stored in the TS_FIFO, that is, the data amount can be appropriately maintained. As a result, the transport stream can be smoothly transmitted from the buffer means to the TS_FIFO, and the digital broadcast signal can be smoothly retransmitted.

  Further, the reproduction rate clock frequency generation means generates the reproduction rate clock frequency based on the number of bytes of the transport stream existing between the program clock references (PCR), so that the reproduction rate clock based on the reference clock frequency in the broadcasting station. A reproduction rate clock frequency equivalent to the frequency can be generated. Thereby, the reproduction rate clock frequency of the transport stream transmitted from the buffer means (or TS_FIFO) can be matched with the reproduction rate clock frequency in the broadcasting station, and the digital broadcast signal can be retransmitted smoothly.

  Furthermore, the generated reproduction rate clock frequency can be corrected using specific information (PCR). As a result, an appropriate reproduction rate clock frequency can always be maintained, and smooth re-transmission of digital broadcast signals can be maintained.

  Another feature of the present invention is that the digital broadcast signal retransmission apparatus further comprises reference clock frequency generation means for oscillating at a preset reference clock frequency, and the reproduction rate clock frequency correction means includes the extraction rate clock frequency correction means. The generated reproduction rate clock frequency may be corrected based on the specified information and the reference clock frequency.

  According to this, it is possible to correct the reproduction rate clock frequency at low cost without separately providing an expensive oscillation device using, for example, rubidium. Therefore, the amount of data temporarily stored in the buffer means (or TS_FIFO) can be appropriately maintained, and the digital broadcast signal can be retransmitted at a low cost in, for example, a difficult viewing area.

  Another feature of the present invention is that the digital broadcast signal retransmission apparatus further detects an increase or decrease in the data amount of the transport stream temporarily stored in the buffer means by comparing with a predetermined reference data amount. The reproduction rate clock frequency correction means comprises a stored data amount increase / decrease detection means and is generated when an increase in the amount of data temporarily stored in the buffer means is detected by the stored data amount increase / decrease detection means. The generated reproduction rate clock frequency is corrected by increasing the stored data amount increase / decrease detection means, and the generated reproduction rate clock frequency is decreased when the decrease in the amount of data temporarily stored in the buffer means is detected by the storage data amount increase / decrease detection means. There is also to correct it.

  According to this, by detecting (monitoring) an increase or decrease in the amount of data temporarily stored in the buffer means, it is possible to correct an error (shift) in the reproduction rate clock frequency that may occur in a long cycle. it can. That is, the short-term reproduction rate clock frequency can be corrected based on the specific information and the reference clock frequency. However, for example, if the reference clock frequency generation means has a minute oscillation error, if this minute oscillation error accumulates over the long term, an error occurs in the reproduction rate clock frequency, and the buffer amount of the buffer means May be difficult to maintain properly.

  In contrast, by detecting (monitoring) an increase or decrease in the amount of data temporarily stored in the buffer means, and correcting the reproduction rate clock frequency so as to maintain the amount of stored data appropriately, a long period of time can be obtained. It is possible to prevent an error (shift) in the reproduction rate clock frequency that may occur, and appropriately correct the reproduction rate clock frequency.

  Another feature of the present invention is that, based on attribute information included in the transport stream temporarily stored in the buffer means, the transport packet forming the stored transport stream is the digital broadcast. A packet analysis means for analyzing whether one of the 13 segments forming a signal is a one-segment packet or a 12-segment packet for 12 of the 13 segments; and the analysis by the packet analysis means Based on the packet separation means for separating the transport packets forming the transport stream sent from the buffer means into the 1-segment packet and the 12-segment packet as a hierarchy, and the packet separation means. The 1-segment packet FIFO and the 12-segment packet FIFO that store and output the 1-segment packet and the 12-segment packet, respectively, in the input order, and the orthogonal frequency division multiplex modulation means includes the 1-segment packet FIFO and The 1-segment packet and the 12-segment packet may be acquired from the 12-segment packet FIFO at a predetermined clock frequency, and orthogonal frequency division multiplexing modulation may be transmitted again as a digital broadcast signal.

  In this case, when the digital broadcast signal retransmission apparatus includes table generation means for generating a table used by the packet separation means to separate the one-segment packet based on the analysis of the attribute information by the packet analysis means. Good.

  In these cases, the attribute information is included in the transport stream temporarily stored in the buffer means, for example, and a program association table (list of programs related to reproduction of the transport stream) ( PAT) and information including a program map table (PMT) representing image and sound identification corresponding to the program.

  According to these, the digital broadcast signal transferred via the IP line, more specifically, the transport stream transmitted as a predetermined block unit can be retransmitted as a 1 + 12 segment digital broadcast signal. In this case, a program association table (PAT) and a program map table (PMT) included in the transport stream stored in the buffer means are analyzed, and a table for separating one segment packet is generated based on this analysis. Thus, based on this table, the transport packets forming the transport stream can be promptly (in real time) separated into 1 segment packets and 12 segment packets as a hierarchy.

  As a result, the transport stream can be smoothly transmitted from the buffer means (or TS_FIFO) at the reproduction rate clock frequency, and the 1-segment packet and the 12-segment packet separated as a hierarchy are smoothly subjected to orthogonal frequency division multiplexing modulation. Can be retransmitted as a 1 + 12 segment digital broadcast signal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a configuration of a digital broadcast signal retransmitting apparatus S that retransmits a terrestrial digital television broadcast signal according to the present embodiment. The digital broadcast signal retransmitting device S receives a terrestrial digital television broadcast signal transmitted from a broadcasting station H via a transmitting antenna A, and the receiving device 1 and an Internet line (IP line). And an OFDM modulation device 2 connected thereto.

  Here, the digital terrestrial television broadcast signal transmitted from the transmission antenna A will be briefly described. In the broadcasting station H, video data and audio data are encoded and compressed at a reference clock frequency (for example, 27 MHz), and a video elementary stream and an audio elementary stream are generated for each predetermined data unit. Then, the video elementary stream and the audio elementary stream are each packetized into transport packets by adding a stream ID representing the attribute, reproduction time information, and the like. The transport packet packetized in this way is transmitted from the transmission antenna A as a terrestrial digital television broadcast signal by performing OFDM modulation. Here, when transmitting a transport packet, the broadcasting station H uses a program clock reference (PCR) packet as a predetermined packet in order to adjust the buffer amount on the receiving side for a transport stream in which video and audio transport packets are continuous. Insert transport packets at time intervals and send transport packets.

  For example, the receiving apparatus 1 is installed in an area where a digital terrestrial television broadcast signal can be satisfactorily received, receives a terrestrial digital television broadcast signal transmitted from the transmission antenna A, that is, an OFDM-modulated transport packet, and receives the same. The received transport packet is demodulated by a known method. Then, the receiving apparatus 1 sends a transport stream, in which demodulated transport packets are continuous, to the Internet line as a predetermined block unit (for example, a multiple of 188 bytes). Here, the receiving apparatus 1 outputs a transport stream in which PCR packets are inserted at regular time intervals.

  In the OFDM modulation apparatus 2, as shown in FIG. 2, the TS buffer circuit 200 takes in and temporarily stores the transport stream transferred through the Internet line. Then, the transfer rate calculation circuit 201 refers to the transport packet that forms the transport stream stored in the TS buffer circuit 200, and transfers the transport stream packet using the two PCR packets included in the transport stream. Calculate the rate.

  That is, the transfer rate calculation circuit 201 calculates the transfer rate based on the number of bytes existing between two PCR packets included in the transport stream. Here, the PCR packet is inserted at a predetermined time interval at the broadcasting station H as described above. For this reason, a transfer rate equivalent to the transfer rate at the broadcasting station H can be calculated by using the number of bytes between these two PCR packets. Then, the transfer rate calculation circuit 201 supplies the calculated transfer rate to the frequency generation circuit 202. The frequency generation circuit 202 generates a byte clock frequency based on its own reference operation clock frequency and the supplied transfer rate, and sets the generated byte clock frequency as the reproduction rate clock frequency of the transport stream.

  The transport packet data temporarily stored in the TS buffer circuit 200 is sequentially supplied to the TS_FIFO circuit 203. The TS_FIFO circuit 203 is a FIFO (First In First Out) circuit that sequentially inputs the data of the transport stream packet from the TS buffer circuit 200 as a byte string and sequentially transmits the input data as a byte string. Then, the TS_FIFO circuit 203 sequentially transmits the data of the transport stream packet as a byte string based on the reproduction rate clock frequency set by the frequency generation circuit 202. As a result, the byte sequence sequentially transmitted from the TS_FIFO circuit 203 is sequentially transmitted at a byte clock frequency equivalent to the byte clock frequency in the broadcasting station H.

  The byte sequence corresponding to the PCR packet included in the data of the transport stream is extracted by the PCR extraction circuit 204 from each byte sequence sequentially transmitted from the TS_FIFO circuit 203 at the reproduction rate clock frequency, and the STC counter 205 and the error detection circuit are extracted. 207 is supplied. The STC counter 205 increments the counter value using the clock frequency of 27 MHz supplied from the 27 MHz transmitter 206.

  The error detection circuit 207 sequentially stores time information represented by a byte string corresponding to the PCR packet supplied from the PCR extraction circuit 204, and the time information and a counter value (time information) supplied from the STC counter 205. ) To determine whether or not an error has occurred in the reproduction rate clock frequency set by the frequency generation circuit 202. Hereinafter, operations of the PCR packet extraction circuit 204, the STC counter 205, and the error detection circuit 207 will be described.

  The PCR extraction circuit 204 first extracts a byte sequence corresponding to the first PCR packet after the transmission of the byte sequence from the TS_FIFO circuit 203, and continuously extracts the extracted byte sequence from the STC counter 205 and error detection. This is supplied to the circuit 207. In this case, when the STC counter 205 sequentially acquires the bytes corresponding to the first PCR packet and acquires the last byte of the byte string corresponding to the PCR packet, the STC counter 205 uses the clock frequency of the 27 MHz transmitter 206 to calculate the counter value. Start incrementing. On the other hand, when the error detection circuit 207 acquires the byte sequence corresponding to the first PCR packet, the error detection circuit 207 temporarily stores the first time information represented by the byte sequence.

  Next, when the PCR extraction circuit 204 continuously extracts the byte string corresponding to the next PCR packet from the byte strings sequentially transmitted from the TS_FIFO circuit 203, the extracted byte string is continuously extracted to the STC counter 205. And supplied to the error detection circuit 207. In this case, the STC counter 205 supplies the counter value at the time of obtaining the last byte of the byte sequence corresponding to the PCR packet supplied from the PCR extraction circuit 204 to the error detection circuit 207. The counter value is incremented again by using the clock frequency of the 27 MHz transmitter 206 from the time when the byte is acquired.

  Then, the error detection circuit 207 includes the counter value (time information) incremented by the STC counter 205, the time information represented by the byte string corresponding to the next PCR packet extracted by the PCR extraction circuit 204, and the first time. The difference value with the section time information calculated from the information is calculated. When the error detection circuit 207 calculates this difference value, it updates the time information represented by the byte sequence corresponding to the first (previous) PCR to the time information represented by the byte sequence corresponding to the next PCR. And store temporarily. If the calculated difference value is “0”, the error detection circuit 207 delays the reproduction stream clock frequency of the transport stream sent from the TS_FIFO circuit 203, that is, the byte clock frequency generated by the frequency generation circuit 202. It is determined that no error has occurred.

  On the other hand, if the calculated difference value is not “0”, the error detection circuit 207 determines that an error such as a delay has occurred in the reproduction rate clock frequency of the TS_FIFO circuit 203, and causes the error to the frequency generation circuit 202. Send information. Thereby, the frequency generation circuit 202 corrects the set reproduction rate clock frequency, that is, the generated byte clock frequency. Specifically, the frequency generation circuit 202 corrects the reproduction rate clock frequency by increasing or decreasing the byte clock frequency to be generated based on the difference value calculated by the error detection circuit 207.

  The data amount detection circuit 208 detects an increase or decrease in the data amount of the transport stream temporarily stored in the TS buffer circuit 200. That is, the data amount detection circuit 208 has a data amount of the transport stream stored in the TS buffer circuit 200 with respect to a preset reference storage data amount (for example, set in a range of 512 KB to 2 MB). Whether it is increasing or decreasing is monitored and detected over a long period of time.

  That is, as described above, the reproduction rate clock frequency set by the frequency generation circuit 202 is the reproduction rate clock frequency generated in the short term by the PCR extraction circuit 204, the STC counter 205, the 27 MHz transmitter 206, and the error detection circuit 207. Correct errors such as (byte clock frequency) delay. By the way, in particular, the clock frequency oscillated by the 27 MHz oscillator 206 may have an extremely small oscillation error. As described above, even in a situation where the 27 MHz transmitter 206 has an extremely small oscillation error, the error can be corrected by correcting the reproduction rate clock frequency in a short period as long as the processing is performed in the OFDM modulator 2. The TS_FIFO circuit 203 can sequentially send out the byte sequence by correcting the error and correcting the error at the reproduction rate clock frequency.

  However, when a transport stream is acquired from the outside via the Internet line, if a very small oscillation error in the 27 MHz transmitter 206 accumulates over a long period of time, the buffer amount of the TS buffer circuit 200 is appropriately set by the accumulated oscillation error. May not be maintained (constantly). That is, if the oscillation error accumulates and, for example, the corrected reproduction rate clock frequency decreases, the byte sequence sent out from the TS_FIFO circuit 203, in other words, the amount of data decreases, and as a result, the TS buffer circuit 200 is temporarily stored. The amount of data in the stored transport stream increases. On the other hand, when the corrected reproduction rate clock frequency increases, the amount of data transmitted from the TS_FIFO circuit 203 increases, and as a result, the amount of data in the transport stream temporarily stored in the TS buffer circuit 200 decreases.

  For this reason, the data amount detection circuit 208 detects (monitors) the data amount of the transport stream stored in the TS buffer circuit 200 over the long term, and the stored data amount tends to increase or decrease. It is determined whether it is in. When a tendency for the data amount to increase or decrease is detected, information representing these trends is output to the long-term increase / decrease correction calculation circuit 209.

  The long-term increase / decrease correction calculation circuit 209 corrects the byte clock frequency set by the frequency generation circuit 202, that is, the reproduction rate clock frequency of the transport stream, based on the detection result by the data amount detection circuit 208. That is, if the data amount temporarily stored in the TS buffer circuit 200 tends to increase based on the detection result of the data amount detection circuit 208, the long-term increase / decrease correction calculation circuit 209, for example, plays the playback rate in units of several Hz. Calculate a correction frequency to increase the clock frequency. On the other hand, if the amount of data temporarily stored in the TS buffer circuit 200 tends to decrease, for example, a correction frequency for reducing the reproduction rate clock frequency is calculated in units of several Hz. Then, the long-term increase / decrease correction calculation circuit 209 outputs the calculated correction frequency to the frequency generation circuit 202. Thus, the frequency generation circuit 202 corrects the reproduction rate clock frequency by increasing or decreasing the byte clock frequency to be generated based on the calculated correction frequency.

  In addition, regarding the transport packet data transmitted from the TS buffer circuit 200, the PAT / PMT analysis unit 210 determines whether it is a PAT (Program Association Table) packet and a PMT (Program Map Table) packet constituting the transport stream. Analyze. More specifically, the PAT / PMT analysis unit 210 extracts the PAT packet from the transport packet data sent from the TS buffer circuit 200, and the PID (Packet Identity) as an identifier of the PAT packet is “0”. It is analyzed whether or not. Here, a packet whose PID of the PAT packet is not “0” is treated as an invalid packet.

  If the PID of the PAT packet is “0”, the PAT / PMT analysis unit 210 analyzes the PMT packet related to the PAT packet, and the program represented by the PMT packet is a program for one segment. It is determined whether or not. Then, the PAT / PMT analysis unit 210 extracts the PID of the video transport packet (data) and the PID of the audio transport packet (data) stored in the analyzed PMT packet, and uses these PIDs as a table. It is set in the one segment layer PID table circuit 211.

  As described above, when a PID table for one segment is set in the one-segment layer PID table circuit 211, the hierarchical control circuit 212, based on this PID table, out of byte sequences sequentially transmitted from the TS_FIFO circuit 203, Based on the byte string corresponding to the PID of the data of the port packet, a transport packet for one segment that matches the PID set in the table is determined. Then, when the byte sequence corresponding to the transport packet for one segment is sequentially transmitted from the TS_FIFO circuit 203, the hierarchical control circuit 212 stores these byte sequences in the layer A_FIFO circuit 213 by switching.

  On the other hand, when a byte sequence corresponding to a transport packet other than one segment, that is, for 12 segments is sequentially transmitted from the TS_FIFO circuit 203, the hierarchical control circuit 212 stores these byte sequences in the layer B_FIFO circuit 214 by switching. To do. Note that when the byte sequence sequentially transmitted from the TS_FIFO circuit 203 corresponds to a NULL packet, the hierarchical control circuit 212 treats it as an invalid packet and sends these byte sequences to the layer A_FIFO circuit 213 and the layer B_FIFO circuit 214. Is not stored.

  As described above, when the byte strings are stored in the layer A_FIFO circuit 213 and the layer B_FIFO circuit 214, the FIFO circuits 213 and 214 obtain the byte clock frequency used for OFDM modulation from the OFDM modulator 215, respectively. Then, the layer A_FIFO circuit 213 and the layer B_FIFO circuit 214 send a byte string corresponding to the stored transport packet to the OFDM modulator 215 based on the acquired byte clock frequency.

  At this time, the layer A_FIFO circuit 213 and the layer B_FIFO circuit 214 correct the PCR value of the PCR packet represented by the stored byte string based on the acquired byte clock frequency and send it out. If the layer A_FIFO circuit 213 and the layer B_FIFO circuit 214 do not store a byte string corresponding to the transport packet, the layer A_FIFO circuit 213 and the layer B_FIFO circuit 214 send a NULL packet to the OFDM modulator 215.

  Thus, when the transport packet is transmitted, the OFDM modulator 215 performs quadrature modulation on the transport packet in accordance with a well-known OFDM modulation method, and transmits it through the transmission antenna 216 as a terrestrial digital television broadcast signal of 1 + 12 segments. To do.

  As can be understood from the above description, according to the above-described embodiment, the transfer rate calculation circuit 201 and the frequency generation circuit 202 use the PCR packet included in the transport stream transferred via the Internet line to broadcast. A byte clock frequency (reproduction rate clock frequency) equivalent to the byte clock frequency (reproduction rate clock frequency) in the station H can be calculated, and the TS_FIFO circuit 203 is calculated based on the calculated byte clock frequency (reproduction rate clock frequency). Can be operated. As a result, the TS_FIFO circuit 203 can transmit a byte string at a byte clock frequency (reproduction rate clock frequency) equivalent to that of the broadcasting station H. As a result, the transport stream temporarily stored in the TS buffer circuit 200 Can be promptly sent to the TS_FIFO circuit 203. Thereby, the buffer amount in the TS buffer circuit 200 can be maintained within a certain range. Therefore, by using the Internet line, the equipment cost can be greatly reduced and the terrestrial digital television broadcast signal can be retransmitted smoothly.

  Further, the PAT / PMT analysis unit 210 can analyze a PAT packet and a PMT packet included in a transport stream transferred via the Internet line, and determine a transport packet for one segment. Further, the hierarchical control circuit 212 corresponds to the transport packet for one segment sent from the TS_FIFO circuit 203 based on the setting table of the one-segment layer PID table 211 set based on the analysis of the PAT / PMT analysis unit 210. The bit string to be stored can be stored in the layer A_FIFO circuit 213.

  On the other hand, the hierarchical control circuit 212 can store, in the layer B_FIFO circuit 214, a bit string corresponding to the 12-segment transport packet sent from the TS_FIFO circuit 203 based on the setting table of the one-segment layer PID table 211. Accordingly, the 1 + 12 segment terrestrial digital television broadcast signal can be finally transmitted by combining the transport packet for 1 segment and the transport packet for 12 segment. In addition, since a transport packet for 1 segment and a transport packet for 12 segments can be separated in real time using a preset table, a 1 + 12 segment terrestrial digital television broadcast signal can be retransmitted smoothly. .

  The implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the above embodiment, a transport stream including two PCR packets is temporarily stored in the TS buffer circuit 200. Then, the transfer rate calculation circuit 201 calculates the transfer rate based on the number of bytes existing between two PCR packets stored in the TS buffer circuit 200. However, if the transport stream is continuously stored in the TS buffer circuit 200, it is sufficient that at least one PCR packet is included in the transport stream, or PCR is performed for each predetermined transport stream. It only needs to include a packet.

  In this case, the transfer rate calculation circuit 201 detects a PCR packet from the transport stream stored in the TS buffer circuit 200. Then, the transfer rate calculation circuit 201 detects the next PCR packet from the transport stream stored in the TS buffer circuit 200 successively in succession. As a result, the transfer rate calculation circuit 201 calculates the transfer rate using the total number of bytes existing between the two detected PCR packets, so that the frequency generation circuit 202 has the byte clock frequency (reproduction rate) at the broadcasting station H. A byte clock frequency (reproduction rate clock frequency) equivalent to the clock frequency) can be generated and set. Therefore, the same effect as the above embodiment can be obtained.

  Moreover, in the said embodiment, it implemented so that the digital broadcast signal retransmission apparatus S might be provided with the receiver 1 which receives the terrestrial digital broadcast signal transmitted as a radio wave from the broadcast station H. However, when the broadcasting station H sends a transport stream to the Internet line in predetermined block units as indicated by broken lines in FIG. 1, the receiving apparatus 1 is omitted and the OFDM modulation apparatus 2 is connected to the Internet line. It is also possible to directly acquire the transport stream transmitted from the broadcasting station H via the network. Even in this case, since the transport stream is transmitted from the broadcasting station H via the Internet line, the same effect as the above embodiment can be obtained.

  Furthermore, in the above embodiment, the broadcast signal of the terrestrial digital television broadcast is transferred via the Internet line. However, for example, a BS digital television broadcast signal may be transferred via the Internet line, or a CS digital television broadcast signal may be transferred via the Internet line. Even in this case, the digital broadcast signal can be retransmitted smoothly and inexpensively as in the above embodiment.

It is a figure for demonstrating the outline of the digital broadcast signal retransmission apparatus which concerns on embodiment of this invention. FIG. 2 is a block diagram schematically showing a configuration of the OFDM modulation apparatus in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reception apparatus, 2 ... OFDM modulation apparatus, 200 ... TS buffer circuit, 201 ... Transfer rate calculation circuit, 202 ... Frequency generation circuit, 203 ... TS_FIFO circuit, 204 ... PCR extraction circuit, 205 ... STC counter, 206 ... 27MHz transmission 207 ... Error detection circuit, 208 ... Data amount detection circuit, 209 ... Long-term increase / decrease correction calculation circuit, 210 ... PAT / PMT analysis unit, 211 ... One-segment layer PID table circuit, 212 ... Hierarchy control circuit, 213 ... Layer A_FIFO circuit , 214 ... layer B_FIFO circuit, 215 ... OFDM modulator, 216 ... transmission antenna, S ... digital broadcast signal retransmission apparatus

Claims (9)

A transport stream formed in a predetermined block unit using a transport packet representing a digital broadcast signal is acquired via an IP line, and the acquired transport stream is subjected to orthogonal frequency division multiplexing to be converted into a digital broadcast signal again. A digital broadcast signal retransmission apparatus comprising orthogonal frequency division multiplex modulation means for sending,
Buffer means for temporarily storing the acquired transport stream in a predetermined block unit;
Specific information extracting means for extracting specific information to be inserted into the acquired transport stream at a predetermined interval;
Reproduction rate clock frequency generation means for generating a reproduction rate clock frequency of the temporarily stored transport stream using the extracted specific information;
A digital broadcast signal retransmission apparatus comprising: a reproduction rate clock frequency correction unit that corrects the generated reproduction rate clock frequency using the extracted specific information. In the digital broadcast signal retransmission apparatus according to claim 1,
The transport stream temporarily stored in the buffer means is sent to the TS_FIFO that stores and outputs the transport stream in the input order.
The reproduction rate clock frequency generation means includes:
A digital broadcast signal retransmission apparatus for generating a reproduction rate clock frequency for sequentially transmitting the transport stream stored in the TS_FIFO. In the digital broadcast signal retransmission apparatus according to claim 1,
Furthermore, a reference clock frequency generation means for oscillating at a preset reference clock frequency is provided,
The reproduction rate clock frequency correction means includes:
The digital broadcast signal retransmitting device, wherein the generated reproduction rate clock frequency is corrected based on the extracted specific information and the reference clock frequency. In the digital broadcast signal retransmission apparatus according to claim 1,
Furthermore, a storage data amount increase / decrease detecting means for detecting an increase / decrease in the data amount of the transport stream temporarily stored in the buffer means by comparing with a predetermined reference data amount,
The reproduction rate clock frequency correction means includes:
When the increase in the amount of data temporarily stored in the buffer means is detected by the stored data amount increase / decrease detection means, the generated reproduction rate clock frequency is increased and corrected, and the stored data amount increase / decrease detection means The digital broadcast signal retransmitting apparatus, wherein when the decrease in the amount of data temporarily stored in the buffer means is detected, the generated reproduction rate clock frequency is decreased and corrected. The specific information is
2. The digital broadcast signal retransmission apparatus according to claim 1, wherein the digital broadcast signal retransmission apparatus is a program clock reference (PCR) inserted to adjust a buffer amount when the transport stream is temporarily stored. In the digital broadcast signal retransmission apparatus according to claim 5,
The reproduction rate clock frequency generation means includes:
The digital broadcast signal retransmitting apparatus, wherein the reproduction rate clock is generated based on the number of bytes existing between program clock references (PCR) included in the transport stream. In the digital broadcast signal retransmission apparatus according to claim 1,
Based on attribute information included in the transport stream temporarily stored in the buffer means, one of the 13 segments in which the transport packet forming the stored transport stream forms the digital broadcast signal Packet analysis means for analyzing whether the segment is a one-segment packet relating to a segment or a 12-segment packet relating to twelve of the thirteen segments;
Packet separation means for separating the transport packets forming the transport stream sent from the buffer means into a hierarchy of the 1 segment packet and the 12 segment packet based on the analysis by the packet analysis means;
A 1-segment packet FIFO and a 12-segment packet FIFO for storing and outputting the 1-segment packet and the 12-segment packet separated by the packet separation means, respectively, in the order of input;
The orthogonal frequency division multiplex modulation means includes
The digital device characterized in that the 1-segment packet and the 12-segment packet are acquired from the 1-segment packet FIFO and the 12-segment packet FIFO at a predetermined clock frequency, and orthogonal frequency division multiplexing modulation is transmitted again as a digital broadcast signal. Broadcast signal retransmission device. In the digital broadcast signal retransmission apparatus according to claim 7,
A digital broadcast signal retransmission apparatus comprising table generation means for generating a table used by the packet separation means for separating the one-segment packet based on the analysis of the attribute information by the packet analysis means. .   The attribute information is included in the transport stream temporarily stored in the buffer means, and corresponds to a program association table (PAT) representing a list of programs related to reproduction of the transport stream and the program 9. The digital broadcast signal retransmission apparatus according to claim 7 or 8, wherein the information includes a program map table (PMT) representing image and audio identification.

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