Abstract:
A program information transport apparatus comprises a update unit for accepting a request for a change in either one of program information and transmission control information stored in a memory, and for updating the contents of the memory according to the change at predetermined update times to update the program information. An information management unit can acquire the program information from the memory and then furnish the acquired program information at predetermined transport times to transport the program information. A transport unit then transports the program information from the information management unit to receivers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a program information transport apparatus and a method for transporting program information about digital broadcast programs. 
     2. Description of the Prior Art 
     Referring now to FIG. 10, there is illustrated a block diagram showing the structure of a prior art program information transport apparatus. In the figure, reference numeral  1  denotes a PES (Packetized Elementary Stream)/TS (Transport Stream) packetizing unit for packetizing media data such as coded video data, coded audio data, and coded other data so as to generate a plurality of PES streams (each PES is a stream of frames), and for TS-packetizing the plurality of PES streams into a plurality of fixed-length TS packet streams,  2  denotes a memory for storing program information including program specific information (PSI) and the transport cycle time for the program information,  3  denotes a TS packetizing unit for acquiring the program information from the memory  2  at predetermined transport times to start transport of program information, the predetermined transport times being preset based on the transport cycle time, and for packetizing the program information into a stream of TS packets from the acquired program information from the memory  2 , and  4  denotes a TS packet multiplexor for multiplexing the TS-packetized media data from the PES/TS packetizing unit  1  and the TS-packetized program information from the TS packetizing unit  3  into a single output stream for transmission, called transport stream (TS). 
     In operation, in accordance with ITU-T Rec. H.220.0|ISO/IEC 13818-1 (MPEG-2 Systems), the sender of a digital broadcast has to multiplex program specific information PSI and media data into a single output stream. The program specific information PSI is the one needed for receivers to demultiplex the single output stream from the sender into the program information and the media data. The program specific information PSI is divided into four tables including indispensable tables and optional tables. The program specific information PSI is constructed from a program association table or PAT and a program map table or PMT. 
     When the PES/TS packetizing unit  1  receives media data such as coded video data, coded audio data, and coded other data, it generates PES streams for audio, video, and other data, and after that, generates a plurality of fixed-length TS packet streams from those PES streams so as to transmit the plurality of fixed-length packets over transmission paths. On the other hand, the TS packetizing unit  3  acquires the program information including the program specific information PSI from the memory  2  at the predetermined transport times to start transport of program information (e.g., at predetermined intervals of 100 msec after the packetizing process is started), which are preset based on the transport cycle time for the program information, so as to generate a stream of TS packets from the acquired program information from the memory  2 . 
     After the PES/TS packetizing unit  1  furnishes the plurality of TS-packetized media data streams and the TS packetizing unit  3  furnishes the stream of TS-packetized program information, the TS packet multiplexor  4  multiplexes them into a single output, i.e. a transport stream TS and then sends out the transport stream TS. This technique of multiplexing media data and program information into a single output stream for transmission is disclosed in, for example, Japanese Patent Application Publication (KOKAI) No. 9-284238. 
     A problem with the prior art program information transport apparatus so constructed as mentioned above is thus that although the prior art apparatus can multiplex program information and media data into a single output stream for transmission, when there is a change in the contents of any one of digital broadcast programs it needs to suspend the process of multiplexing the program information and media data, and then modify the contents of the memory  2  because it cannot accept the change while continuing to perform the process of multiplexing the program information and media data, whereby forcing the multiplexor to suspend the process of multiplexing the program information and media data until the process of modifying the contents of the memory  2  is complete. 
     SUMMARY OF THE INVENTION 
     The present invention is made to overcome the above problem. It is therefore an object of the present invention to provide a program information transport apparatus and a method for transporting program information about digital broadcast programs, capable of modifying the program information or the like while continuing to perform the process of multiplexing the program information and media data into a single output stream for transmission. 
     In accordance with one aspect of the present invention, there is provided a program information transport apparatus comprising: a storage unit for storing program information about digital broadcast programs as well as transmission control information including a transport cycle time for the program information; a update unit for accepting a request for a change in either one of the program information and transmission control information stored in the storage unit, and for updating the contents of the storage unit according to the change at predetermined update times to update the program information; an information management unit for acquiring the program information from the storage unit and then furnishing the acquired program information at predetermined transport times to transport the program information, the predetermined transport times being preset based on the transport cycle time stored in the storage unit; and a transport unit for transporting the program information from the information management unit to outside the program information transport apparatus. 
     Preferably, the transport unit multiplexes the program information from the information management unit and media data into a single output stream, and then transports the single output stream. 
     The storage unit can store, as the transmission control information, predetermined update times to update the program information, a transport start time to start transport of the program information, a transport end time to finish transport of the program information, and a transport priority assigned to the program information. Further, the update unit can accept a request for a change in either one of the predetermined update times, the transport start time, the transport end time, and the transport priority, which are stored in the storage unit. 
     Preferably, the information management unit starts to transfer the program information to the transport unit after the transport start time for the program information. 
     Preferably, the information management unit can also finish transferring the program information to the transport unit after the transport end time for the program information. The information management unit can also erase the program information from the storage unit after the transport end time for the program information. 
     Preferably, the storage unit stores a plurality of pieces of program information, the information management unit sequentially transfers the plurality of pieces of program information to the transport unit in order of transport priority if some of the plurality of pieces of program information have to be transported at the same transport times. 
     In accordance with a preferred embodiment of the present invention, the program information transport apparatus further includes an extracting unit for extracting program information from multiplexed data, into which media data and the program information are multiplexed, transported thereto from outside the apparatus. Further, the storage unit can further store program information that is the same as program information previously-extracted by the extracting unit until the extracting means extracts the current program information. The storage unit can also store a transport cycle time for the program information. The program information transport apparatus can further include a second update unit for determining whether or not there is a change in the extracted program information by comparing the extracted program information with the previous program information stored in the storage unit, and for updating the contents of the storage unit according to the program information extracted by the extracting unit only if there is a change in the extracted program information. The information management unit also acquires the program information from the storage unit and then furnishes the acquired program information to the transport unit at predetermined transport times to transport the program information, the predetermined transport times being preset based on the transport cycle time stored in the storage unit. 
     In accordance with another aspect of the present invention, there is provided a program information transport apparatus comprising: an extracting unit for extracting program information from multiplexed data, into which media data and the program information are multiplexed, transported thereto from outside the apparatus; a storage unit for storing program information, which is the same as previously-extracted program information, until the extracting means extracts the current program information, and for storing a transport cycle time for the program information; a update unit for determining whether or not there is a change in the program information extracted by the extracting unit by comparing the extracted program information with the previous program information stored in the storage unit, and for updating the previous program information stored in the storage unit according to the program information extracted by the extracting unit, only if there is a change in the extracted program information; an information management unit for acquiring the program information from the storage unit and then furnishing the acquired program information at predetermined transport times to transport the program information, the predetermined transport times being preset based on the transport cycle time; and a transport unit for transporting the program information transferred thereto from the information management unit to outside the program information transport apparatus. 
     In accordance with another aspect of the present invention, there is provided a method of transporting program information, comprising the steps of: prestoring program information about digital broadcast programs and transmission control information including a transport cycle time for the program information in a memory; accepting a request for a change in either one of the program information and the transmission control information stored in the memory; updating the contents of the memory according to the change at predetermined update times to update the program information; acquiring the program information from the memory and then multiplexing the acquired program information and media data into an output stream at predetermined transport times to transport the program information, the predetermined transport times being preset based on the transport cycle time; and transporting the output stream to outside. 
     In accordance with another aspect of the present invention, there is provided a method of transporting program information transport, comprising the steps of: extracting program information from multiplexed data, into which media data and the program information are multiplexed, transported thereto from outside, storing program information, which is the same as previously-extracted program information, in a memory until the current program information is extracted from the multiplexed data, and storing a transport cycle time for the program information in the memory; determining whether or not there is a change in the program information by comparing the extracted program information with the previous program information; updating the contents of the memory according to the extracted program information, only if there is a change in the program information; acquiring the program information from the memory and then furnishing the acquired program information at predetermined transport times to transport the program information, the predetermined transport times being preset based on the transport cycle time; and transporting the program information to outside. 
    
    
     Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the structure of a program information transport apparatus according to a first embodiment of the present invention; 
     FIG. 2 is a flow diagram showing the operation of the program information transport apparatus and a method of transporting program information according to a first embodiment of the present invention; 
     FIG. 3 is a table showing an example of the program information; 
     FIG. 4 is a table showing an example of transmission control information; 
     FIG. 5 is a table showing an information control table; 
     FIG. 6 is a block diagram showing the structure of a program information transport apparatus according to a variant of the first embodiment of the present invention; 
     FIG. 7 is a block diagram showing the structure of a program information transport apparatus according to another variant of the first embodiment of the present invention; 
     FIG. 8 is a block diagram showing the structure of a program information transport apparatus according to a second embodiment of the present invention; 
     FIG. 9 is a block diagram showing the structure of a program information transport apparatus according to a variant of the second embodiment of the present invention; and 
     FIG. 10 is a block diagram showing the structure of a prior art program information transport apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     Referring next to FIG. 1, there is illustrated a block diagram showing the structure of a program information transport apparatus according to a first embodiment of the present invention. In the figure, reference numeral  11  denotes an information providing unit for managing pieces of program information each about one channel, each including program specific information PSI, and pieces of transmission control information each including a transport cycle time for each piece of program information, update times for each piece of program information, a transport start time to start transport of each piece of program information, a transport end time to finish transport of each piece of program information, and a transport priority assigned to each piece of program information, for accepting a change in either each piece of program information or each piece of transmission control information, and for providing or notifying a program information generating unit  12  of the change,  13  denotes a program information generating section of the program information generating unit  12 , for converting the notified change in either the program information or the transmission control information into a transport format (i.e., data in the section-type format defined by MPEG-2 Systems), which is defined by either an American ATSC Standard (Program and System Information Protocol for Terrestrial and Cable) or a Japanese ARIB standard (which defines program arrangement information for use with digital broadcasts),  14  denotes a memory for storing both the plural pieces of program information and the plural pieces of transmission control information, and  15  denotes a program information control section for referring to the predetermined update times for each piece of program information, part of which is the one that has been changed and converted in the transport format by the program information generating section  13 , or which is associated with the changed piece of transmission control information converted in the transport format, for storing (or overwriting) the change converted in the transport format in either the program information or the transmission control information in the memory  14  at the next predetermined update time for the program information, and for acquiring each piece of program information from the memory  14  at predetermined transport times for each piece of program information, which are preset based on the corresponding transport cycle time stored in the memory  14 , and then transferring each piece of program information to a TS packetizing section  18 . The TS packetizing section  18  generates a stream of TS packets from the acquired program information from the memory  114 . 
     In addition, reference numeral  16  denotes a multiplexing unit,  17  denotes a PES (Packetized Elementary Stream)/TS (Transport Stream) packetizing section for packetizing media data such as coded video data, coded audio data, and coded other data so as to generate a plurality of PES streams, and for generating a plurality of TS packet streams from those PES streams, and  19  denotes a TS packet multiplexor for multiplexing the TS-packetized media data from the PES/TS packetizing section  17  and the TS-packetized program information from the TS packetizing section  18  into a transport stream TS for transmission, and for transporting the transport stream TS to outside the apparatus. 
     Referring next to FIG. 2, there is illustrated a flow diagram showing the operation of the program information transport apparatus, and a method of transporting program information according to the first embodiment of the present invention. 
     The memory  14  of the program information control unit  15  stores pieces of program information each about one channel (see FIG. 3) including program specific information PSI, and pieces of transmission control information (see FIGS. 4 and 5) each including a transport cycle time for each piece of program information, update times for each piece of program information, a transport start time to start transport of each piece of program information, a transport end time to finish transport of each piece of program information, a transport priority assigned to each piece of program information, and an address specifying a memory location where the top of each piece of program information is stored. When the next transport time for each piece of program information comes, which is preset based on the corresponding transport cycle time stored in the memory  14 , in step ST 1 , the program information control section  15 , in step ST 2 , acquires each piece of program information from the memory  14  and then transfers the program information to the TS packetizing section  18 . 
     For example, since the transport cycle time for the program information about channel M is set to 400 msec and the transport start time to start transport of the program information is set to 10:30, as shown in FIG. 4, the program information control unit  15  acquires the program information about channel M and then transfers the program information to the TS packetizing unit  18  at predetermined intervals of 400 msec after 10:30. 
     The TS packetizing section  18  then, in step ST 3 , TS-packetizes the program information into a stream of TS packets and transfers it to the TS packet multiplexor  19  every time the TS packetizing section  18  receives the program information from the program information control section  15 . On the other hand, when the PES/TS packetizing section  17  receives media data such as coded video data, coded sound data, and other data, it, in step ST 4 , packetizes those media data into PES streams, and after that, generates a plurality of TS fixed-length packet streams from those PES streams in step ST 5 . 
     In this way, the PES/TS packetizing section  17  transfers the plurality of streams of TS-packetized media data to the TS packet multiplexor  19  and the TS packetizing section  18  transfers the stream of TS-packetized program information to the TS packet multiplexor  19 . The TS packet multiplexor  19  then, in step ST 6 , multiplexes those TS packet streams into a transport stream TS, and furnishes the transport stream TS to outside the apparatus, in step ST 7 . MPEG-2 Systems can be used as the method of multiplexing the TS packet streams from the PES/TS packetizing section  17  and the TS packetizing section  18 . As an alternative, another method can be used. 
     When during the broadcast of a program, the need for changing either the program information or the transmission control information about the program arises, the information providing unit  11  can accept the change in either the program information or the transmission control information. When the information providing unit  11 , in step ST 8 , receives the change, it notifies the program information generating section  13  of the change. 
     When the program information generating section  13  is notified of the change by the information providing unit  11 , it converts the change in the program information into a transport format defined by either the American ATSC Standard or the Japanese ARIB standard, for example. In the case of changing the transmission control information, the program information generating section  13  only furnishes the change in the transmission control information, just as it is, without converting it into a transport format. 
     When the program information control section  15  receives either the change in the program information, which has been converted in the predetermined transport format, or the change in the transmission control information, it, instep ST 9 , refers to the next update time for the program information which is the one part of which has been changed or which is associated with the changed transmission control information, and determines if the next update time comes. When the next update time comes, the program information control section  15 , in step ST 10 , stores the change in either the program information or the transmission control information in the memory  14  (or overwrites the previous program information with the change). 
     For example, when the program information about channel M is changed at 20:50, the program information about channel M in the memory  14  is updated at 21:00 because the next update time is 21:00. In this case, although the not-yet-updated (or previous) program information and media data are multiplexed by the TS packet multiplexor until 21:00, the updated program information and media data will be multiplexed after 21:00. 
     The reason why the program information is not updated until the next update time, that is, the program information is updated at the next update time is that if the program information is updated in real time, an allowable change in the program information associated with a program being broadcasted (or on the air), such as a change in the source number of the video or sound, forces the audiences to change the program information such as the source number of the vide or sound, thereby putting a large load on the audiences, which is not appropriate from the viewpoint of broadcast services. The update times for the program information are also the ones when the program currently being broadcasted is changed to another program (see FIG.  3 ), and there is no program on the air at one update time, where commercials running during programs are not any programs. Therefore, even though the program information such as a source number is updated at one update time, the load imposed on the audiences is small and therefore such a update of the program information at one update time for the program information is not a problem from the viewpoint of broadcast services. 
     As previously explained, in accordance with the first embodiment of the present invention, the program information transport apparatus is so constructed as to accept a change in either each piece of program information or each piece of transmission control information stored in the memory  14 , and update the contents of the memory  14  according to the change. Accordingly, the first embodiment offers the advantage of being able to change either each piece of program information or each piece of transmission control information while continuing to perform a process of multiplexing each piece of program information and media data into a single output stream. 
     Numerous variants can be made in the exemplary embodiment mentioned above. In a variant of the first embodiment, after the transport end time for each piece of program information, the program information control section  15  finishes the process of transferring each piece of program information to the TS packetizing section  18  and then erases each piece of program information and the transmission control information associated with each piece of program information from the memory. For example, in the case of channel Q as shown in FIG. 5, the program information control section  15  finishes the process of transferring the program information about channel Q to the TS packetizing section  18  and then erases the program information about channel Q and the transmission control information about channel Q stored in the memory after 11:00, because the transport end time for channel Q is set to 11:00. Accordingly, the variant offers the advantage of being able to automatically finish the process of multiplexing the program information about a channel that have not offered any programs, as well as to reduce the storage amount of the memory  14 , thereby reducing the size of the memory  14 . 
     In another variant, when some pieces of program information have the same transport time, the program information control section  15  can be so constructed as to sequentially transfer the plurality of pieces of program information to the TS packetizing section  18  in order of transport priority as shown in FIG.  4 . For example, when the PMT about channel M, which is a part of the program information about channel M, has the same transport times as the PMT about channel N, the program information control section  15  transfers the PMT about channel N first, and after that, transfers the PMT about channel M because the PMT about channel N has a higher priority (priority “1”) than the PMT about channel M (priority “2”). Accordingly, the other variant offers the advantage of being able to transport important program information with first priority. 
     In another variant, the TS packetizing section  18  can be disposed within the program information generating unit  12 , as shown in FIG. 6, instead of being disposed within the multiplexing unit  16 . This variant offers the same advantages as provided by the first embodiment and the other variants mentioned above. 
     In another variant, the program information control section  15  can be disposed within the multiplexing unit  16 , as shown in FIG. 7, instead of being disposed within the program information generating unit  12 . This variant offers the same advantages as provided by the first embodiment and the other variants mentioned above. Needless to say, the program information generating unit  12  and the multiplexing unit  16  can be integrated into a single unit. 
     Second Embodiment 
     Referring next to FIG. 8, there is illustrated a block diagram showing the structure of a program information transport apparatus according to a second embodiment. In the figure, reference numeral  21  denotes a program information extracting unit for receiving multiplexed data, including media data and program information, transported thereto from another broadcaster, for extracting the program information from the multiplexed data and determining whether or not there is a change in the extracted program information, and for transferring the extracted program information to a program information editing unit  23  if there is a change in the extracted program information, and  22  denotes a memory for storing the program information that has been extracted and transferred by the program information extracting unit  21 , and  23  a program information editing unit for editing the previous program information stored in the memory  22  according to the extracted program information from the program information extracting unit  21  so as to keep the program information stored in the memory  22  up to date. 
     In addition, reference numeral  24  denotes a memory for storing program information transferred thereto from the program information editing unit  23  as well as the transmission control information associated with the program information, including the transport cycle time for the program information,  25  denotes a program information control section for acquiring the program information from the memory  24  and then transferring the program information to a TS packetizing section  26  at predetermined transport times for the program information, which are preset based on the transport cycle time for the program information. The TS packetizing unit  26  then packetizes the program information from the program information control section  25  into a stream of TS packets, i.e., a transport stream TS, and transports the transport stream TS to outside the apparatus. 
     The program information transport apparatus according to the second embodiment of the present invention is so constructed as to extract program information from multiplexed data, into which media data and the program information are multiplexed and which are transported thereto from any one of a plurality of other broadcasters, and then transport only the extracted program information. When the program information extracting unit  21  receives multiplexed data that includes media data and program information and that are transported thereto from any one of a plurality of other broadcasters, it extracts the program information included in the multiplexed data. Multiplexed data from any one of a plurality of other broadcasters can include program information that is not the one associated with any media data which the plurality of other broadcasters broadcast. The program information extracting unit  21  does not extract such program information from the multiplexed data. After the program information extracting unit  21  extracts the program information included in the multiplexed data, it determines whether or not there is a change in the extracted program information. To this end, the program information extracting unit  21  compares the extracted program information with the previously-extracted program information, which is stored in a memory (not shown). 
     Only if there is a change in the extracted program information, that is, only if the extracted program information differs from the previously-extracted program information, the program information extracting unit  21  transfers the extracted program information to the program information editing unit  23 , so as to reduce traffic between the program information extracting unit  21  and the program information editing unit  23 . 
     When the program information editing unit  23  receives the extracted (or changed) program information from the program information extracting unit  21 , it edits the previous program information stored in the memory  22  according to the changed program information. After the program information editing unit  23  has finished bringing the program information stored in the memory  22  up to date, it transfers the program information to the program information control section  25 . The program information editing unit  23  can transfer the program information to the program information control section  25  only when it has edited the program information stored in the memory  22  so as to reduce traffic between the program information editing unit  23  and the program information control section  25 . 
     When the program information control section  25  receives the program information from the program information editing unit  23 , it stores the program information in the memory  24 . After that, the program information control section  25  acquires the program information from the memory  24  and then transfers the program information to the TS packetizing section  26  at the next predetermined transport time, which is preset based on the transport cycle time for the program information. The transport cycle time that is stored in the memory  24  is preset according to the transport rate for the TS packetizing section  26 . 
     When the TS packetizing section  26  receives the program information from the program information control section  25 , it packetizes the program information into a stream of TS packets, i.e., a transport stream TS, and then transports the transport stream TS to outside the apparatus. 
     As previously explained, in accordance with the second embodiment of the present invention, the program information extracting unit  21  extracts program information from multiplexed data transported thereto from any one of a plurality of other broadcasters, and determines whether or not there is a change in the extracted program information, and the program information editing unit updates the contents of the memory  22  and hence the contents of the memory  24  according to the extracted program information only when there is a change in the program information included in the multiplexed data. Accordingly, the second embodiment of the present invention offers the advantage of being able to transport the latest program information associated with media data from any one of a plurality of other broadcasters. 
     In a variant of the second embodiment mentioned above, the program information transport apparatus can multiplex the program information that has been extracted from multiplexed data transported thereto from any one of a plurality of other broadcasters, and its own media data, and then transport the multiplexed data, instead of transporting only the program information extracted from the multiplexed data, as shown in FIG.  9 . This variant can offer the same advantage as provided by the second embodiment mentioned above. In FIG. 9, the same reference numerals as shown in FIG. 1 designate the same components as the above-mentioned first embodiment of the present invention. Further, reference numeral  27  denotes a memory for temporarily storing either program information or transmission control information transferred thereto from the program information generating section  13 , and  28  denotes a transfer control unit for transferring either the program information or the transmission control information transferred thereto from the program information generating section  13  to the program information editing unit  23 . 
     Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.