JP7481957B2 - Gateway device and program - Google Patents

Description

The present invention relates to a gateway device and a program.

In satellite broadcasting of 4K and 8K video, the IP (Internet Protocol)-based MMT (MPEG Media Transport) method is used instead of the MPEG-2TS used in conventional digital broadcasting (see Non-Patent Document 1). In the MMT method, one programming channel (hereinafter referred to as a "package") can contain multiple video and audio components (hereinafter referred to as "assets"). In addition, in the MMT method, a PA (Package Access) message is transmitted that contains an MP (MMT Package) table that describes location information such as the destination IP address and destination port number of the asset data along with the asset data. A receiving device, which is a viewing device such as a television, first receives the PA message and refers to the location information contained in the PA message to obtain the data of each asset, as shown in FIG. 8.

Of the multiple assets that make up a package, data for some of the assets can be transmitted over a communication path (e.g., a closed network such as CATV), which is a transmission path different from the broadcast path. Broadcasting and communication integrated services that use broadcast paths and communication paths are being considered. An example of such a broadcasting and communication integrated service is shown in Figure 9.

In the broadcasting and communication cooperation service shown in FIG. 9, the main content, that is, the main video and audio, are transmitted over the broadcasting path, and the sub-content, that is, the sub-video, is transmitted over the communication path. According to the broadcasting and communication cooperation service shown in FIG. 9, the viewer can switch between the main video and the sub-video, or enjoy them simultaneously. As shown in FIG. 9, the PA message is transmitted over the broadcasting path, and the MP table included in the PA message describes the location information of the assets transmitted over the broadcasting path and the assets transmitted over the communication path.

ARIB STD-B60, "Media transport method using MMT in digital broadcasting"

In broadcasting and communication integration services using the MMT method, it is expected that both main content and sub-content will be transmitted using the UDP (User Datagram Protocol)/IP multicast method. In addition, a viewing style being considered for the future will be one in which received content is streamed over a home network and viewed on viewing devices such as televisions and smartphones connected to the home network.

Wireless LANs (Local Area Networks) are often used as home networks. Compared to wired LANs, wireless LANs experience more frequent packet loss. In multicast systems, processing such as error correction and packet retransmission at the wireless layer is not performed, so in the above-mentioned viewing format, even if multicast data that arrives at each home is sent directly to the home network, it may not be received by the viewing device. Therefore, it is conceivable to provide a gateway device at the entrance to the home network, and use the gateway device to convert the multicast data transmitted via the broadcast path and/or communication path into unicast data and send it to the home network.

In the multicast method, a viewing device can receive the content it wishes to receive by joining a multicast group that corresponds to that content. The IP address of the multicast group is set as the destination IP address of the multicast data. The gateway device can convert the multicast data to unicast data by replacing the destination IP address (multicast group address) set in the multicast data with the IP address of the viewing device. In the unicast method, processing such as error correction and packet retransmission is performed in the wireless layer, so the viewing device can receive the content even if packet loss occurs.

However, simply replacing the destination IP address (multicast group address) set in the multicast data with the IP address of the viewing device will result in an inconsistency with the location information in the PA message, and the viewing device will not be able to obtain the content assets.

The object of the present invention is to provide a gateway device and a program that can solve the above-mentioned problems and more reliably receive asset data that constitutes a package transmitted by multicast.

To solve the above problem, the gateway device according to the present invention is a gateway device that relays data of multiple assets constituting a package, transmitted by a multicast method, to a receiving device connected via a network, and includes a replacement unit that receives the multicast data of the multiple assets and location information of the multiple assets, converts the data into unicast data in which a destination address set in the data is replaced with the address of the receiving device, and rewrites the location information in accordance with the replacement and transmits the data to the receiving device via the network.

In the gateway device according to the present invention, data of some of the assets constituting the package is transmitted via a first transmission path, and data of the remaining assets is transmitted via a second transmission path, the location information includes a destination address of the asset data, and the replacement unit replaces the destination address set in the first data transmitted via the first transmission path and the destination address set in the second data transmitted via the second transmission path with the address of the receiving device, and rewrites the destination address included in the location information in response to the replacement.

In addition, in the gateway device according to the present invention, the location information further includes a destination port number, which is the port number of the destination port for receiving the data of the asset, and when the first port number set in the first data and the second port number set in the second data are the same, the first port number and the second port number are replaced with different port numbers, and the destination port number included in the location information is rewritten in accordance with the replacement.

The gateway device according to the present invention further includes a control unit that stores a correspondence relationship between a destination address of the asset data, a destination port number of a destination port for receiving the asset data, and an alternative destination port number that is an alternative to the destination port and is a port number of an alternative destination port that is different for each destination address, and when the destination addresses set in the first data and the second data are different and the first port number and the second port number are the same, the replacement unit replaces the first port number and the second port number with the corresponding alternative destination port number based on the stored correspondence relationship.

To solve the above problem, the program according to the present invention causes a computer to function as the above-mentioned gateway device.

The gateway device and program according to the present invention make it possible to more reliably receive data constituting a package transmitted by multicast.

1 is a diagram illustrating an example of the configuration of a data communication system according to an embodiment of the present invention. 2 is a sequence diagram showing an example of the operation of the gateway device and the audiovisual device shown in FIG. 1 . 2 is a diagram showing an example of a correspondence relationship between a multicast group, a destination port number, and an alternative destination port number, which is stored in a control unit of the gateway device shown in FIG. 1 . 2 is a diagram illustrating an example of a destination address and a destination port number being replaced by a replacement unit illustrated in FIG. 1 . 2 is a diagram showing an example of rewriting of location information by a PA message rewriting unit shown in FIG. 1; 1. FIG. 4 is a diagram illustrating another example of destination address and destination port number replacement by the replacement unit illustrated in FIG. 1. FIG. 4 is a diagram showing another example of rewriting of location information by the PA message rewriting unit shown in FIG. A diagram showing an example of a broadcasting and communication cooperation service in which different packages are transmitted via a broadcast path and a communication path. FIG. 7 is a diagram showing an example of location information included in the PA message shown in FIG. 6 . FIG. 13 is a diagram for explaining acquisition of asset data by referring to location information. FIG. 1 is a diagram illustrating an example of a broadcasting and communication cooperation service.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is a diagram showing an example of the configuration of a data communication system 1 according to one embodiment of the present invention.

As shown in FIG. 1, the data communication system 1 according to this embodiment includes a gateway device 10 and a viewing device 20 as a receiving device. The viewing device 20 is a device for viewing content, such as a television, smartphone, or tablet terminal installed in a user's home. The gateway device 10 and the viewing device 20 are connected via a home network such as a wireless LAN.

The gateway device 10 is provided at the entrance of the home network to which the viewing device 20 is connected. The gateway device 10 receives data of multiple assets constituting one organized channel (package). Specifically, the gateway device 10 receives data of assets constituting the main content of the package transmitted via a broadcast path (first transmission path) in a multicast manner. The gateway device 10 also receives data of assets constituting the sub-content of the package transmitted via a communication path (second transmission path) in a multicast manner. The gateway device 10 also receives a PA message transmitted via a broadcast path, which includes location information of multiple assets constituting the package. The location information is information that is referenced when acquiring the asset data, such as the destination IP address and destination port number of the asset data. The gateway device 10 converts the received multicast data (packets) into unicast data (packets) and transmits it to the viewing device 20 via the home network. The gateway device 10 also rewrites the location information included in the PA message in accordance with the conversion of the multicast data to unicast data described above, and transmits it to the viewing device 20.

The viewing device 20 refers to the location information included in the PA message transmitted from the gateway device 10 via the home network, acquires asset data of the main content and sub-content, and presents the content to the user.

Next, the configuration of the gateway device 10 and the viewing device 20 will be described with reference to FIG. 1. First, the configuration of the gateway device 10 will be described.

As shown in FIG. 1, the gateway device 10 includes a control unit 11 and a transfer unit 12.

The control unit 11, which will be described later in detail, stores an IP address IP _d of a multicast group corresponding to the content received by the viewing device 20, a destination port number P d which is the port number of a port (destination port) for receiving data addressed to the IP address IP _d in the viewing device 20, and an alternative destination port number P _a which is the port number of a port (alternative destination port) that substitutes for the destination port, in association with each other. The control unit 11 obtains the correspondence between the IP address IP _d , the destination port number P _d , and the alternative destination port number P _a by exchanging control signals with the control unit 21 of the viewing device 20, which will be described later. The control unit 11 outputs a replacement instruction to the replacement unit ₁₂ , which instructs the replacement of the destination address (IP address IP _d ) and the destination port number P _d included in the received multicast data, based on the stored correspondence.

The replacement unit 12 receives data (packets) of assets of the main content and sub-content transmitted via an external (broadcast path and communication path (e.g., a closed network such as CATV)) from outside the home network to which the viewing device 20 is connected. The replacement unit 12 also receives a PA message including location information transmitted via the broadcast path. The location information includes information referenced when acquiring data of multiple assets that constitute one package. Therefore, the location information includes not only assets transmitted via the broadcast path, but also information referenced when acquiring assets transmitted via a communication path that constitute the same package as the assets transmitted via the broadcast path.

In the received multicast data (packet), the IP address IP _d of the multicast group in which the viewing device 20 participates is set as the destination address, and the destination port number P _d of the destination port for receiving data addressed to the IP address IP _d is set. The replacement unit 12 replaces the IP address IP _d set in the multicast data with the IP address of the viewing device 20 in accordance with the replacement instruction output from the control unit 11. In this way, the replacement unit 12 converts the received multicast data into unicast data. In addition, the replacement unit 12 replaces the destination port number P _d set in the multicast data _with an alternative destination port number Pa associated with the destination port number P _d , as necessary, as will be described in detail later.

The replacement unit 12 also includes a PA message rewriting unit 121. The PA message rewriting unit 121 rewrites the location information in response to the replacement of the IP address IP _d (and destination port number P _d ) set in the multicast data described above. The replacement unit 12 transmits the unicast data generated by converting the multicast data and the PA message with the rewritten location information to the audiovisual device 20 via the home network.

Next, we will explain the configuration of the viewing device 20.

As shown in FIG. 1, the viewing device 20 includes a control unit 21, a decoder 22, and a presentation unit 23.

The control unit 21 exchanges control signals with the control unit 11, and notifies the gateway device 10 of the IP address IP _d , destination port number P _d , and alternative destination port number P _a of the multicast group in which the viewing device 20 wishes to join. When the IP address IP _d , destination port number P _d , and alternative destination port number P _a of the multicast group are stored in association with each other in the gateway device 10, the control unit 21 outputs a receive/present instruction to the decoder 22 to receive unicast data transmitted from the gateway device 10 and present content based on the received data.

When a reception and presentation instruction is output from the control unit 21, the decoder 22 refers to the location information included in the PA message transmitted from the gateway device 10 via the home network, and receives the content (main content and sub-content) data transmitted by unicast. The decoder 22 decodes the received data, obtains the video and audio signals of the content, and outputs them to the presentation unit 23.

The presentation unit 23 plays the video and audio signals output from the decoder 22 and presents the content.

Next, the operation of the gateway device 10 and the viewing device 20 will be described with reference to the sequence diagram shown in FIG. 2. IGMP (Internet Group Management Protocol) is a protocol that controls the operation of the viewing device 20 to join a multicast group. The following describes an example in which IGMP is used. The following describes an example in which IPv4 is used as the IP address protocol. When IPv6 is used, a protocol called MLD (Multicast Listener Discovery) can be used. In this case, the viewing device 20 sends an MLD Join message instead of an IGMP Join message described later, and sends an MLD Leave message instead of an IGMP Leave message, but the other procedures are the same as when IPv4 is used.

When joining a multicast group, the control unit 21 transmits an IGMP Join message to the gateway device 10 requesting participation in the multicast group (step S101). The IGMP Join message includes the IP address IP _d of the multicast group to which the user wishes to join, and the destination port number P _d of the destination port that receives data addressed to the IP address IP _d . The destination port number P _d is a port number associated with the content to be transmitted, and is notified by a broadcast station (not shown) before or at the start of content distribution, together with the IP address IP _d of the multicast group to which the content is distributed. When the viewing device 20 transmits the IGMP Join message to the gateway device 10, it opens the destination port and waits for content data (packets). The viewing device 20 repeatedly transmits the IGMP Join message at regular intervals.

The control unit 11 receives an IGMP Join message sent from the viewing device 20. If the home network to which the viewing device 20 is connected supports the multicast method, the multicast data is relayed to the viewing device 20 and received by the viewing device 20 according to the normal sequence defined by IGMP.

If the home network does not support the multicast method, when the control unit 11 receives the IGMP Join message, it transmits an alternative destination port request message by unicast to the destination port of the viewing device 20 (step S102). The alternative destination port request message is a message requesting notification of the port number (alternative destination port number P _a ) of an alternative destination port that is an alternative to the destination port. The control unit 11 can know in advance whether the home network to which the viewing device 20 is connected supports the multicast method.

When the control unit 21 receives the alternative destination port request message transmitted from the gateway device 10, it selects a port to be an alternative destination port from among the available ports, and transmits an alternative destination port reply message to the gateway device 10 (step S103). The alternative destination port reply message includes the IP address IP _d of the multicast group in which the viewing device 20 wishes to participate, the destination port number P _d , and the alternative destination port number P _a . When the destination port number P _d , which will be described later, is replaced with the alternative destination port number P _a , the viewing device 20 opens the alternative destination port and waits for unicast data.

When the control unit 11 receives the alternative destination port response message transmitted from the viewing device 20, the control unit 11 stores the IP address IP _d , the destination port number P _d , and the alternative destination port number P _a included in the alternative destination port response message in association with each other (step S104). After storing the association between the IP address IP _d , the destination port number P _d , and the alternative destination port number P _a of the multicast group, the control unit 11 outputs a replacement instruction to the replacement unit 12.

When the control unit 11 outputs a replacement instruction, the replacement unit 12 receives the asset data of the main content transmitted over the broadcast path by multicasting and the asset data of the sub-content transmitted over the communication path by multicasting (step S105). The received multicast data includes the IP address IP _d of the multicast group and the destination port number P _d .

The replacement unit 12 converts the received multicast data into unicast data. Specifically, the replacement unit 12 replaces the IP address IP _d of the multicast group included in the multicast data with the IP address of the viewing device 20. Furthermore, the replacement unit 12 replaces the destination port number P _d included in the received multicast data with the alternative destination port number Pa stored in the control unit 11 in association with the destination port number P _{d ,} as necessary. Furthermore, the PA message rewriting unit 121 rewrites the location information included in the PA message in response to the replacement of the IP address IP _d (and the destination port number P _d ) described above (step S106).

The transfer unit 12 converts the multicast data and generates unicast data, which it then transmits to the viewing device 20 via the home network (step S107). As described above, the viewing device 20 repeatedly transmits an IGMP Join message at regular time intervals. However, once the gateway device 10 starts a relay operation to convert the multicast data into unicast data and transmit the data to the viewing device 20, it does not transmit an alternative destination port request message even if it receives an IGMP Join message from the viewing device 20.

When the gateway device 10 receives an IGMP Leave message from the viewing device 20 requesting to leave the multicast group (step S108), the gateway device 10 ends the packet relay operation. That is, the gateway device 10 repeats the above-mentioned processes from step S105 to step S107 until it receives an IGMP Leave message from the viewing device 20.

As a content viewing mode on the viewing device 20, there is a viewing mode in which contents (IP flows) with only the IP address _IPd of the multicast group being different and the destination port number being the same are simultaneously viewed. For example, in a sports broadcast, a camera's video is transmitted via a broadcast channel, and another camera's video is transmitted via a communication channel (e.g., a closed network such as CATV), and these videos are simultaneously viewed on the viewing device 20.

When multicast data is relayed to the viewing device 20, there is a method of simply rewriting the IP address _IPd of the multicast group set in the multicast data to the IP address of the viewing device 20. However, this method does not allow distinction between IP flows in the above-mentioned viewing format in which only the multicast group IP address _IPd is different and the destination port number _Pd is the same. On the other hand, in this embodiment, the destination port number _Pd can be replaced with an alternative destination port number _Pa for each IP flow, so that each IP flow can be distinguished even in the above-mentioned viewing format.

Next, a specific example of the replacement of the IP address IP _d (and the destination port number P _d ) set in the data of the multicast method and the rewriting of the location information according to the replacement will be described. In the following, it is assumed that the control unit 11 stores the IP address IP _d of the multicast group, the destination port number P _d and the alternative destination port number P _a in association with each other as shown in FIG. 3. In the example shown in FIG. 3, the IP address IP _d of the multicast group of the main content "224.0.0.1" is associated with the destination port number P _d "51216" of the destination port associated with the main content, and the alternative destination port number P _a "50000" of the alternative destination port. In addition, the IP address IP _d of the multicast group of the subcontent "224.0.0.2" is associated with the destination port number P _d "51216" of the destination port associated with the subcontent, and the alternative destination port number P _a "50001" of the alternative destination port. As shown in FIG. 3, the control unit 11 stores a multicast group address (destination address of asset data), a destination port number _Pd of a destination port for receiving the asset data, and an alternative destination port number Pa, which is an alternative to the destination port and is a port number of an alternative destination port that is different for each destination address, in association with _{each other} .

Figure 4A is a diagram showing an example of the operation of the replacement unit 12. In Figure 4A, in order to simplify the figure, the control unit 11, control unit 21, and presentation unit 23 are omitted. In the following, it is assumed that the IP address of the viewing device 20 is "192.168.0.100". In the following, as described with reference to Figure 9, it is assumed that data (first data) of some assets (main content assets) of the multiple assets that make up one package is transmitted over a broadcast path (first transmission path), and data (second data) of the remaining assets (sub-content assets) is transmitted over a communication path (second transmission path).

In the example shown in Fig. 4A, the IP address _IPd "224.0.0.1" and the destination port number _Pd "51216" are set in the data of the main content asset, while the IP address _IPd "224.0.0.2" and the destination port number _Pd "51216" are set in the data of the sub content asset.

The replacement unit 12 replaces the IP address _IPd "224.0.0.1" set in the asset data of the main content with the IP address "192.168.0.100" of the viewing device 20. The replacement unit 12 also replaces the IP address _IPd "224.0.0.2" set in the asset data of the sub-content with the IP address "192.168.0.100" of the viewing device 20.

As described with reference to Fig. 3, the alternative destination port number Pa "50000" is stored in association with the IP address _IPd "224.0.0.1" and the destination port number _Pd "51216". Also, the alternative destination port number _Pa "50001" is stored in association with the IP address _IPd "224.0.0.2" and the destination port number _Pd "51216". Based on this correspondence, the replacement unit 12 replaces the destination port number _Pd "51216" set in the asset data of the main content with the alternative destination port number _{Pa "} 50000", and replaces the destination port number _Pd "51216" set in the asset data of the sub-content with the alternative destination port number _Pa "50001".

Therefore, the replacement unit 12 transmits, to the viewing device 20, data of the asset of the main content in the unicast method, in which the IP address of the viewing device 20, "192.168.0.100" and the alternative destination port number P _a "50000" are set. The replacement unit 12 also transmits, to the viewing device 20, data of the asset of the sub-content in the unicast method, in which the IP address of the viewing device 20, "192.168.0.100" and the alternative destination port number P _a "50001" are set.

The PA message rewriting unit 121 rewrites the location information included in the PA message in accordance with the above-mentioned replacement of the IP address IP _d and the destination port number P _d . The rewriting of the location information by the PA message rewriting unit 121 will be described with reference to FIG.

In the example shown in FIG. 4B, "location_type" is included as location information for the main content asset. "Location_type" indicates the type of location information. In the example shown in FIG. 4B, "0x00" is set as "location_type." "0x00" indicates that the IP data flow is the same as the IP data flow in which the PA message including the MP table containing the location information is transmitted.

In the example shown in FIG. 4B, the location information of the subcontent asset includes "location_type", "ipv4_src_addr", "ipv4_dst_addr", and "dst_port". "0x01" is set as "location_type". "0x01" indicates an IPv4 data flow. "ipv4_src_addr" indicates a source IP address that is an IP address of the sender of the subcontent, and in the example shown in FIG. 4B, "10.0.0.1" is set. "ipv4_dst_addr" indicates a destination address of the IPv4 data flow, and is set to the IP address IP _d "224.0.0.2" set in the data of the subcontent asset. "dst_port" indicates a destination port number of the IPv4 data flow, and is set to the destination port number P _d "51216" of the destination port of the viewing device 20.

As described above, the destination IP address IP _d "224.0.0.2" set in the asset data of the sub-content is rewritten to the IP address "192.168.0.100" of the audiovisual device 20. Also, the destination port number P _d "51216" set in the asset data of the sub-content is rewritten to the alternative destination port number P _a "50001". Therefore, as shown in FIG. 4B, the PA message rewriting unit 121 rewrites "224.0.0.2" set in "ipv4_dst_addr" included in the location information of the sub-content to "192.168.0.100". Also, as shown in FIG. 4B, the PA message rewriting unit 121 rewrites "51216" set in "dst_port" included in the location information of the sub-content to "50001".

In this way, when the main content and the sub-content form one package and the destination port number _Pd (first port number) of the main content is the same as the destination port number _Pd (second port number) of the sub-content, the replacement unit 12 replaces the destination IP address _IPd and the destination port number _Pd and rewrites the location information.

Figure 5A is a diagram showing another example of the operation of the replacement unit 12. Note that in Figure 5A as well, the control unit 11, the control unit 21, and the presentation unit 23 are omitted.

In the example shown in Fig. 5A, the IP address _IPd "224.0.0.1" and the destination port number _Pd "51216" are set in the data of the main content asset, while the IP address _IPd "224.0.0.2" and the destination port number _Pd "51217" are set in the data of the sub content asset.

The replacement unit 12 replaces the IP address _IPd "224.0.0.1" set in the asset data of the main content with the IP address "192.168.0.100" of the viewing device 20. The replacement unit 12 also replaces the IP address _IPd "224.0.0.2" set in the asset data of the sub-content with the IP address "192.168.0.100" of the viewing device 20.

In the example shown in Fig. 5A, the destination port number _Pd "51216" set in the asset data of the main content is different from the destination port number _Pd "51217" set in the asset data of the sub-content. In this case, the data flow of the main content and the data flow of the sub-content can be distinguished without replacing with the alternative destination port number _Pa . Therefore, the replacement unit 12 does not replace the destination port number _Pd set in the asset data of the main content and the sub-content.

Therefore, the replacement unit 12 transmits to the viewing device 20 unicast main content asset data, to which the viewing device 20's IP address "192.168.0.100" and destination port number _Pd "51216" are set. The replacement unit 12 also transmits to the viewing device 20 unicast sub content asset data, to which the viewing device 20's IP address "192.168.0.100" and destination port number _Pd "51217" are set.

The PA message rewriting unit 121 rewrites the location information in response to the reassignment of the IP address _IPd described above. Rewriting of the location information by the PA message rewriting unit 121 will be described with reference to FIG.

In the example shown in Fig. 5A, only the IP address _IPd is replaced, and the destination port number _Pd is not replaced. Therefore, the PA message rewriting unit 121 rewrites "224.0.0.2" set in "ipv4_dst_addr" included in the location information of the sub-content asset to "192.168.0.100". As shown in Fig. 5B, the PA message rewriting unit 121 does not rewrite "dst_port" included in the location information of the sub-content, but leaves it as "51217".

In this manner, when the destination port number _Pd differs between the main content and the sub-content, the replacement unit 12 replaces the destination IP address _IPd and rewrites the location information.

As shown in FIG. 6, assets constituting different packages may be transmitted over a broadcast path and a communication path. In this case, a PA message is transmitted for each transmission path, including an MP table that describes the location information of the assets constituting the package transmitted over that transmission path.

As an example of a case where assets of different packages are transmitted for each transmission path, as shown in Fig. 4A, the destination port number _Pd set in the data of an asset constituting the main content may be different from the destination port number _Pd set in an asset constituting a sub-content of a package different from the main content. As another example, as shown in Fig. 5A, the destination port number _Pd set in the data of an asset constituting the main content may be the same as the destination port number _Pd set in an asset constituting a sub-content of a package different from the main content. In either case, the operation of the replacement unit 12 to replace the destination IP address _IPd (and the destination port number _Pd ) is the same as the operation described with reference to Figs. 4A and 5A.

4A, when the destination port number _Pd set in the asset data constituting the main content is the same as the destination port number _Pd set in the asset constituting the sub-content, the replacement unit 12 replaces the destination IP address _IPd ("224.0.0.1" and "224.0.0.2") set in the asset data with the IP address ("192.168.0.100") of the audiovisual device 20. The replacement unit 12 also replaces the destination port numbers _Pd ("51216" and "51217") set in the asset data with the alternative destination port numbers Pa ("50000" and "50001").

Also, as shown in FIG. 5A, when the destination port number _Pd set in the data of the asset constituting the main content is different from the destination port number _Pd set in the asset constituting the sub-content, the replacement unit 12 replaces the destination IP address _IPd ("224.0.0.1" and "224.0.0.2") set in the asset data with the IP address of the viewing device 20 ("192.168.0.100").

Even if the destination port number _Pd set in the data of an asset constituting the main content is different from the destination port number _Pd set in an asset constituting a sub-content of a package different from the main content, and even if they are the same, the location information of the assets of the main content and the sub-content will only have "location_type" indicating "0x00" as shown in Fig. 7. Therefore, the PA message rewriting unit 121 relays the location information of the main content and the sub-content to the viewing device 20 as is without rewriting the information.

In this embodiment, an example has been described in which assets of two contents (main content and sub content) are input to the gateway device 10, but this is not limiting. Even when assets of three or more contents are input to the gateway device 10, the replacement unit 12 and the PA message rewriting unit 121 replace the destination IP address _IPd and the destination port number _Pd , and rewrite the location information, by the same process as described in this embodiment.

As described above, in this embodiment, the gateway device 10 includes a replacement unit 12 that, upon receiving data of a plurality of assets transmitted by the multicast method and location information of the plurality of assets, converts the data into unicast method data in which the IP address _IPd set in the data of the plurality of assets is replaced with the address of the viewing device 20. The replacement unit 12 rewrites the location information in accordance with the replacement and transmits it to the viewing device 20 via the network.

By rewriting the location information in response to the change in destination address that accompanies the conversion of data of multiple assets transmitted by multicast to data by unicast, inconsistencies in the location information are eliminated. Therefore, the viewing device 20 can more reliably receive the asset data of the package transmitted by multicast.

In the above-described embodiment, an example is shown in which one viewing device 20 is connected to the home network, but the present invention is not limited to this, and multiple viewing devices 20 may be connected to the home network. In this case, the gateway device 10 relays data transmitted by the multicast method in response to a request from each viewing device 20.

Although not specifically mentioned in the embodiment, a program that causes a computer to function as the gateway device 10 may be provided. The program may also be recorded on a computer-readable medium. The computer-readable medium can be used to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

Alternatively, a chip may be provided that is configured with a memory that stores programs for executing each process performed by the gateway device 10 and a processor that executes the programs stored in the memory and is mounted on the gateway device 10.

The above-mentioned embodiment has been described as a representative example, but it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiment, and various modifications and changes are possible without departing from the scope of the claims. For example, it is possible to combine multiple configuration blocks shown in the configuration diagram of the embodiment into one, or to divide one configuration block.

REFERENCE SIGNS LIST 1 Data communication system 10 Gateway device 11 Control unit 12 Transfer unit 121 PA message rewriting unit 20 Audio-visual device (receiving device)
21 Control unit 22 Decoder 23 Presentation unit

Claims (5)

A gateway device that relays data of a plurality of assets constituting a package, the data being transmitted by a multicast method, to a receiving device connected via a network, comprising:
a gateway device comprising: a reassignment unit that receives the data of the multiple assets in the multicast format and location information of the multiple assets, converts the data into unicast format data in which a destination address set in the data is replaced with an address of the receiving device, rewrites the location information in accordance with the replacement, and transmits the reassigned data to the receiving device via the network. 2. The gateway device according to claim 1,
Among the plurality of assets constituting the package, data of some of the assets is transmitted via a first transmission path, and data of the remaining assets is transmitted via a second transmission path;
The location information includes a destination address of the data of the asset;
The gateway device, wherein the replacement unit replaces a destination address set in first data transmitted via the first transmission path and a destination address set in second data transmitted via the second transmission path with an address of the receiving device, and rewrites a destination address included in the location information in response to the replacement. 3. The gateway device according to claim 2,
The location information further includes a destination port number, which is a port number of a destination port for receiving data of the asset;
When a first port number set in the first data and a second port number set in the second data are identical, the gateway device replaces the first port number and the second port number with different port numbers and rewrites a destination port number included in the location information in accordance with the replacement. 4. The gateway device according to claim 3,
a control unit that stores a correspondence relationship between a destination address of the asset data, a destination port number of a destination port for receiving the asset data, and an alternative destination port number that is an alternative to the destination port and is a port number of an alternative destination port that is different for each destination address;
The gateway device, wherein when the destination addresses set in the first data and the second data are different and the first port number and the second port number are the same, the replacement unit replaces the first port number and the second port number with the corresponding alternative destination port number based on the stored correspondence relationship. A program for causing a computer to function as a gateway device according to any one of claims 1 to 4.

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