JP2008294663A - Receiving device, receiving method, program, and data stream transmission and reception system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time from the reception of an indication to change a channel by a user till the display of a video. <P>SOLUTION: A receiving device includes: a first acquiring means 35 for acquiring a first kind of identification information from a first data stream; an output means 39 for extracting at least video data or sound data from the first data stream to output them; a second acquiring means 35 for acquiring a second kind of identification information from a second data stream during the reception of the first data stream; a storage means 32 for storing the second kind of identification information; and a receiving means 34 for receiving the selection of the data stream including the video data and sound data to be outputted from the output means 39. When the second data stream is selected, the output means 39 extracts at least the video data or the sound data from the second data stream to putput them, based on the second kind of identification information stored in the storage means 32. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a receiving device for receiving a data stream comprising at least one of video data and audio data and identification information for identifying at least one of the video data and audio data from a transmitting device via a network, and receiving The present invention relates to a method, a reception program, and a data stream transmission / reception system.

  In recent years, services that distribute video using an IP (Internet Protocol) network, such as the Internet, have been actively performed due to an increase in communication speed using xDSL and optical fiber technology and progress in compression coding technology. It is becoming. Conventionally, most of these services are targeted at PCs (Personal Computers), but with the digitization and networking of AV devices such as televisions, there are also services targeted at AV devices other than PCs. It has begun.

  In such a service, data distribution is performed by digital data, as in satellite / terrestrial digital broadcasting. In satellite / terrestrial digital broadcasting, MPEG2 (Moving Picture Experts Group 2) can be cited as a compression encoding method. Since MPEG2-TS (MPEG-Transport Stream) is adopted as a transmission method for video and audio streams, MPEG2-TS is also used as a transmission data format in video distribution services using the Internet. Many.

  In MEGP2-TS, it is possible to multiplex and transmit a plurality of packets such as video, audio, and character data in one data stream. The data stream includes data divided into TS packets, and identification information called PID (Packet Identifier) different from each other is assigned to the header portion of each TS packet. Different PIDs are assigned to TS packets related to character information and control information as well as video data and audio data, and transmitted.

  When the data stream is received by the receiving device, TS packets with a PID of zero are first detected. A TS packet with a PID of zero is called a PAT (Program Association Table), and PAT stores PIDs of TS packets related to video information, audio information, character information, and control information called PMT (Program Mapped Table). Yes. The PMT may store the PID of a TS packet in which an ECM (Entitlement Control Message) necessary for decrypting encrypted data is stored.

  That is, in order to reproduce desired content, the receiving device first detects a PAT having a PID of zero, acquires the PID of the PMT from the PAT, and acquires the PID of the video data or audio data packet from the PMT. Then, an instruction for decoding is given based on the PID. If the content is encrypted, the PMT of the ECM TS packet is also acquired from the PMT to acquire information necessary for decryption, and a decryption key is generated and a composite key is used. The video and audio decoding process will be executed. Considering that the content is reproduced from the middle, TS packets such as PAT, PMT, and ECM are periodically transmitted from the transmission device.

  However, if the transmission cycle of TS packets such as PAT is shortened, more transmission bandwidth will be used for data transmission such as PAT, and real-time performance of content transmission may be affected by an increase in network traffic. is there. Normally, TS packets such as PAT and PMT are sent at intervals of 100 msec to 1 sec. When content is played back halfway, even if the transmission cycle is 100 msec, it may take 100 msec to detect PAT and PMT, and there is a possibility that it takes 200 msec in total. This time cannot be ignored as a response time to the user operation.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. 2004-228850 (Patent Document 1) includes means for including a video or audio PID in a response message when notifying a content server of a video transmission request. is suggesting. According to this, since the PID of the video TS packet and the audio TS packet is included in the response message of the video transmission request, when the requested MPEG2-TS data stream arrives, The acquisition of the audio PID has been completed, and it is possible to start the decoding and reproduction processing of the video and audio without performing the video and audio PID detection in order from the detection of the PAT.

  As a method for distributing video content via a network, RTSP (Real Time Streaming Protocol) described in JP-A-2004-228850 (Patent Document 1) and HTTP (Hyper Text Transfer Protocol) are used. In addition to the unicast distribution method, there is a method using IP multicast technology.

An advantage of video distribution using IP multicast over unicast distribution using RTSP or the like is that the load on the network when distributing to a plurality of terminals simultaneously is small. In unicast distribution using RTSP or the like, for example, in order to simultaneously distribute content to a plurality of terminals in one home, a transmission bandwidth of the content × the number of terminals is required. In this case, since one data stream is received by a plurality of terminals, a transmission rate for one line is sufficient. However, since there are disadvantages such as difficulty in fast-forwarding and reproduction, which distribution technology is used is determined by the application.
JP 2004-228850 A

  However, in the method disclosed in Japanese Patent Application Laid-Open No. 2004-228850 (Patent Document 1), it is necessary to include the PID of the video packet or the audio packet in the response message for the video transmission request. Is essential and cannot be used immediately in existing services. Furthermore, in Japanese Patent Application Laid-Open No. 2004-228850 (Patent Document 1), only PIDs of video packets and audio packets can be acquired in advance, and information for decrypting encrypted data is acquired in advance. It is not possible.

  Further, in the video distribution service using the IP multicast described above, since message exchange using HTTP or RTSP as disclosed in Japanese Patent Application Laid-Open No. 2004-228850 (Patent Document 1) is not performed, the client device However, video and audio PIDs cannot be acquired in advance.

  The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to shorten the time from receiving a channel change instruction from a user to outputting an image in a receiving apparatus. is there.

  A receiving apparatus according to the present invention receives a data stream including at least one of video data and audio data and identification information for identifying at least one of video data and audio data from a transmitting apparatus via a network. A receiving means for receiving a plurality of data streams including a first and a second data stream from a transmitting apparatus; a first acquiring means for acquiring first identification information from the first data stream; Output means for extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information; and the second data while the receiving device is receiving the first data stream. Second acquisition means for acquiring second identification information from the stream, and while the receiving device is receiving the first data stream, Storage means for storing the identification information of 2 and reception means for accepting selection of a data stream including video data and audio data output by the output means. When the second data stream is selected, the output means Based on the second identification information stored in the storage means, at least one of video data and audio data is extracted from the second data stream and output.

  In this case, even when a data stream related to one video is received and at least one of one video data and one audio data is extracted and output, another data stream is received and another data stream is received. Identification information relating to at least one of video data and audio data can be acquired. As a result, at least one of video data and audio data can be output from another data stream based on the identification information acquired in advance, and until another video starts to be output after receiving a data stream switching command. Can be shortened. Even in a system where the message exchanged prior to the start of video transmission does not include video data or audio data identification information, the video is displayed after receiving a channel change instruction from the receiving device. The time until it can be shortened.

  Preferably, the transmission device is a relay device for transmitting a data stream received from another transmission device to the reception device.

  Preferably, the apparatus further includes a reproducing unit that decodes at least one of the video data and the audio data extracted by the extracting unit to reproduce at least one of the video and the audio.

  Preferably, the apparatus further comprises request means for requesting the transmission apparatus to transmit the second data stream.

  Preferably, the request unit requests the transmission device to transmit a plurality of different second data streams, and the reception unit receives the plurality of different second data streams transmitted from the transmission device, and performs the second acquisition. The means obtains each second identification information from a plurality of different second data streams while the receiving device is receiving the first data stream, and the storage means receives the first data stream from the plurality of different second data streams. Each of the second identification information is stored therein.

  Preferably, when the acquisition of the second identification information is completed, the requesting unit requests the transmission device to stop transmitting the second data stream, and transmits another data stream including the identification information that has not yet been acquired. Request.

  Preferably, the requesting unit requests the transmission device to transmit a plurality of data streams even during a period in which the output unit stops extracting video data and audio data from the first data stream, and performs the second acquisition. The means obtains the second identification information from the second data stream also during the period, and the storage means stores the second identification information also during the period.

  Preferably, the requesting unit determines whether or not to transmit a message requesting transmission of the second data stream according to a load state of the network to which the receiving device is connected.

  Preferably, the receiving device is connected to the transmitting device via a network capable of designating the transmission priority of data to be transmitted, and the requesting unit has a lower second data stream than the first data stream. Specify transmission priority.

  Preferably, the receiving device is connected to the transmitting device via a network capable of designating a transmission band used for transmission / reception of data, and the requesting unit sets the transmission band used for transmission of the second data stream. A transmission band narrower than the transmission band used for transmitting the first data stream is designated.

  Preferably, the requesting unit transmits a message requesting transmission of the second data stream with a predetermined time interval.

  Preferably, the apparatus further includes a program table receiving unit that receives a program table storing respective program information corresponding to a plurality of different data streams via the network, and the request unit stores each of the program tables stored in the acquired program table. Based on the program information, the transmission apparatus is requested to transmit the second data stream.

  Preferably, the data stream includes composite key generation information for generating a decryption key for decrypting at least one of the encrypted video data and the encrypted audio data, and acquires the composite key generation information from the data stream The apparatus further comprises third acquisition means and decryption key generation means for generating a decryption key from the composite key generation information.

Preferably, the composite key generation information is ECM (Entitlement Control Message).
Preferably, the data stream is MPEG2-TS (Moving Picture Experts Group 2-Transport Stream) data, the data stream includes a PAT (Program Association Table) and a PMT (Program Mapped Table), and the identification information includes video. It includes at least one PID (Program ID) of data and audio data.

  Preferably, the reception device further includes distribution information acquisition means for acquiring distribution information related to a data stream that can be distributed by the transmission device, and the reception means includes a plurality of first and second data streams based on the distribution information. Data stream is received from the transmitter.

  The reception method according to the present invention receives a data stream including at least one of video data and audio data and identification information for identifying at least one of video data and audio data from a transmission device via a network. A receiving method using a device, receiving a plurality of data streams including first and second data streams from a transmitting device, obtaining first identification information from the first data stream, Extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information; and a second data stream while the receiving device is receiving the first data stream. Obtaining the second identification information from the receiver and the receiving device receiving the first data stream And storing each second identification information, accepting selection of a data stream including video data and audio data to be output, and storing the second data stream when the second data stream is selected. And extracting and outputting at least one of video data and audio data from the second data stream based on the second identification information.

  Preferably, the reception method requests the transmission apparatus to transmit a data stream, and requests transmission of another data stream including identification information that has not yet been acquired when acquisition of the second identification information is completed. Further comprising the step of:

  A program according to the present invention provides a computer that can be connected to a transmission apparatus via a network with a data stream including at least one of video data and audio data and identification information for identifying at least one of video data and audio data. A program for receiving, a step of receiving a plurality of data streams including a first data stream and a second data stream from a transmission device, a step of acquiring first identification information from the first data stream, Extracting and outputting at least one of video data and audio data from the first data stream based on the identification information of the first data stream; and receiving the first data stream from the second data stream while the receiving device is receiving the first data stream. Obtaining the second identification information; and Means for storing each second identification information, receiving a selection of a data stream including video data and audio data to be output, and selecting a second data stream while receiving the stream; And extracting and outputting at least one of video data and audio data from the second data stream based on the second identification information stored in the computer.

  The data stream transmission / reception system according to the present invention receives a data stream including a transmission device and at least one of video data and audio data and identification information for identifying at least one of video data and audio data from the transmission device. A data stream transmission / reception system comprising: a receiving unit configured to receive a plurality of data streams including a first data stream and a second data stream from a transmission device; First receiving means for obtaining identification information, output means for extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information, and a receiving apparatus comprising: Obtaining second identification information from the second data stream while receiving the data stream of Selection of a data stream including video data and audio data output from the second acquisition means, storage means for storing each second identification information while the receiving device is receiving the first data stream, and output means Receiving means, and when the second data stream is selected, the output means receives video data and audio from the second data stream based on the second identification information stored in the storage means. Extract and output at least one of the data.

  Preferably, the reception device further includes request means for requesting the transmission device to transmit the data stream, and the request means includes identification information that has not yet been acquired when acquisition of the second identification information is completed. Request transmission of the data stream.

  In the receiving apparatus, it is possible to reduce the time from when an instruction to change the output video data or audio data is received until another video data or audio data is output.

  Embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below. Further, in the following description, the same parts are denoted by the same reference numerals, and when the names and functions of the parts are the same, detailed description of the parts will not be repeated.

[Embodiment 1]
In the following embodiments, a case will be described in which channels are switched in a situation where video content is distributed to a receiving device via a network. And in the following embodiment, although the form where a network is constructed | assembled based on IP (Internet Protocol) is described, it is not limited to these forms. In the following embodiments, examples in which the transport format of video content to be distributed is MPEG2-TS will be described, but the present invention is not limited to these modes.

<MPEG2-TS>
First, a transmission method using MPEG2-TS will be described. In the case of MEGP2-TS, a plurality of video data, audio data, character data, etc. are multiplexed and transmitted in one data stream. For example, a data stream (data stream) related to two video contents, each of which includes two audio data, for example, Japanese audio data and English audio data, is 1 Consider an example that is transmitted as two data streams. In this case, data related to two videos and data related to four sounds are included in one data stream.

  FIG. 1 is a conceptual diagram showing TS packets constituting a data stream. FIG. 2 is a conceptual diagram showing a data stream composed of a plurality of TS packets. As shown in FIG. 1, one data stream is divided into 188-byte TS packets. Different identification information called PID (Packet Identifier) is assigned to the header part of each TS packet. As shown in FIG. 2, a plurality of TS packets are transmitted as one data stream. Further, not only video and audio but also TS packets related to character information and control information are assigned different PIDs in their header portions.

  Next, a method in which the receiving apparatus extracts (extracts) information regarding video and audio from one data stream will be described. When receiving the data stream, the receiving apparatus first detects a TS packet with a PID of zero. A TS packet with a PID of zero is called a PAT (Program Association Table), and the PAT stores a PID of a packet called a PMT (Program Mapped Table). The PMT stores TS packet PIDs related to video, audio, text information, and control information, and is a TS packet for transmitting the PID of each TS packet, and is assigned to each content. For example, when information related to two videos is included in one data stream, and two audios of Japanese and English are included in each video, the PMT of two video contents is included in the PAT. PIDs of TS packets relating to one video and two audios of each video content are stored in the PMT. In addition, the PMT may store a PID of a TS packet related to an ECM (Entitlement Control Message) necessary for decrypting encrypted data.

  That is, in order to reproduce desired content, the receiving apparatus first detects a PAT having a PID of zero from the data stream, acquires the PID of the PMT from the PAT, and acquires the PMT from the data stream based on the PID of the PMT. The PID of the TS packet related to video and audio is acquired from the PMT, and an instruction for decoding is given based on the PID of the TS packet related to video and audio. When video or audio content data is encrypted, the receiving apparatus also acquires the PID of the TS packet in which the ECM is stored from the PMT, and the TS in which the ECM is stored. The packet is detected, data necessary for decryption is acquired, a decryption key is generated, and video and audio decryption processing using a composite key is executed. Considering that video and music content is played back from the middle, TS packets such as PAT, PMT, ECM, etc. are periodically sent from the transmission device.

  Hereinafter, receiver 30a according to Embodiment 1 of the present invention will be described. In the present embodiment, a transmission device (server device) simultaneously distributes data streams to a plurality of reception devices (client devices) using IP multicast technology.

<Data transmission / reception system>
FIG. 3 is a schematic diagram showing the overall configuration of the data stream transmission / reception system. As shown in FIG. 3, the data stream transmission / reception system 1 according to the present embodiment includes a transmission device 10, a relay device 20, and a reception device 30a, which are connected to each other via networks 40 and 50. The network 40 is the Internet. The network 50 is a LAN (Local Area Network) that constructs a network in a home or a company.

  The transmitting device 10 is a content server that distributes video content. As described above, in the present embodiment, the data stream is simultaneously distributed to the plurality of receiving devices 30a, 30a,... Using the IP multicast technology. is doing.

  The relay device 20 is a broadband router that connects the Internet and a LAN to each other. The relay device 20 supports a message requesting transmission of a data stream or a message requesting transmission stop (for example, an IGMP JOIN request and a LEAVE request), and the IP multicast from the transmitting device 10 via the Internet. It has a function of transferring distributed data to the LAN side or stopping the transfer in accordance with a JOIN request and a LEAVE request from a device on the LAN side. The receiving device 30a is a personal computer or a television capable of receiving / reproducing video content distributed via a network.

<Receiving device>
FIG. 4 is a functional block diagram showing a functional configuration of the receiving apparatus. The distribution information acquisition unit 35-3 acquires distribution information regarding a data stream that can be distributed by the transmission device. In addition, the reception unit 31-1 receives a plurality of data streams including the first and second data streams transmitted from the transmission device 10 based on the distribution information acquired by the distribution information acquisition unit 35-3. Receive. The first acquisition unit 35-1 acquires (extracts) first identification information from the first data stream received by the reception unit 31-1.

  However, in the case of unicast distribution using RTSP, there is a method of acquiring a list of contents currently being distributed by accessing a predetermined URL. In addition, in the distribution using multicast, if the data called SI (Service Information) defined in MPEG2-TS is seen, how many channels the video stream currently being distributed is (that is, for which multicast address) Can be recognized). The SI is also transmitted to a specific multicast address. For example, if a multicast address that flows only SI is fixed as a basic specification, the receiving device 30 recognizes a channel currently being distributed at an arbitrary timing. be able to. Further, the distribution information regarding each data stream does not necessarily have to be acquired in advance, and may be stored in a predetermined form in the receiving device 30.

  Based on the first identification information acquired by the first acquisition unit 35-1, the output unit 38-1 receives video data and audio data from the first data stream received by the reception unit 31-1. At least one of these is extracted and output. The second acquisition unit 35-2 acquires second identification information from the second data stream while the reception unit 31-1 is receiving the first data stream. The second acquisition unit 35-2 also acquires ECM (Entitlement Control Message) that is composite key generation information from the second data stream while the reception unit 31-1 is receiving the first data stream. To do. The storage unit 32-1 stores the second identification information acquired by the second acquisition unit 35-2 while the reception unit 31-1 is receiving the first data stream.

  The accepting unit 34-1 accepts selection of the data stream including the video data and audio data output from the output unit 38-1, and the output unit 38-1 receives the output video data and audio data. When the data stream to be included is selected, at least one of video data and audio data is extracted from the second data stream based on the second identification information stored in the storage unit 32-1 Output. Then, the request unit 35-4 requests the transmission apparatus 10 to transmit a plurality of data streams based on the distribution information. The program table acquisition unit 35-5 receives a program table in which program information corresponding to a plurality of different data streams (channels M, N...) Is stored.

  Here, “output” means that audio data is decoded and converted into audio and output, or encoded audio data is output as it is, and further, such as a display or a speaker included in the receiving device This includes not only outputting video data and audio data to the device, but also outputting video data and audio data to an external device such as a television or a hard disk recorder outside the receiving apparatus 30.

  FIG. 5 is a diagram illustrating a hardware configuration when the receiving apparatus is realized using a CPU. As illustrated in FIG. 5, the receiving device 30a according to the present embodiment includes a network connection unit 31 that implements a receiving unit 31-1, a RAM (Random Access Memory) 32 that implements a storage unit 32-1, and a ROM (Read Only Memory) 33, remote control signal receiver 34 realizing reception unit 34-1, first acquisition unit 35-1, second acquisition unit 35-2, distribution information acquisition unit 35-3, and request unit 35-4. And a program table receiving unit 35-5, a CPU (Central Processing Unit) 35, a multiplexing division unit 39 realizing an output unit 38-1, a video decoding unit 36a realizing a reproducing unit 36-1, and an audio decoding unit 36b, the image | video display part 37, and the audio | voice output part 38 are comprised. A decoding unit 36 is configured including a multiplexing division unit 39, a video decoding unit 36a, and an audio decoding unit 36b.

  More specifically, the first acquisition unit 35-1, the second acquisition unit 35-2, the distribution information acquisition unit 35-3, the request unit 35-4, and the program table acquisition unit 35-5 are stored in the ROM 33. It may be realized by the control program and the CPU 35. The output unit 38-1 may be realized by the decoding unit 36, the video display unit 37, the audio output unit 38, and the like. The configuration of other functions is not limited to the correspondence relationship with the hardware as described above.

  A data stream distributed by the networks 40 and 50 is received by the network connection unit 31, subjected to various processes by a control program operating on the CPU 35, and then input to the decoding unit 36. The multiplexing / dividing unit 39 divides the video data and audio data packets from the multiplexed data stream based on the identification information input in advance, and each of them is decoded by the video decoding unit 36a and the audio decoding unit 36b. Thereafter, the video content is reproduced by outputting to the video display unit 37 and the audio output unit 38.

  A control program that operates on the CPU 35 is stored on the ROM 33, read onto the RAM 32 at the time of execution, and executed by the CPU 35. In response to a channel change instruction from the user, a signal received by the remote control signal receiving unit 34 is notified to the control program, and the control program transmits a change request message to the transmission device 10 via the network connection unit 31. The same applies to requests to start or stop playback.

<IP multicast>
Hereinafter, video distribution using IP multicast will be described. Video distribution when using IP multicast uses a multicast address prepared for simultaneous distribution to a plurality of terminals, so that the transmission apparatus 10 has a plurality of transmission destinations (reception apparatuses 30a, 30a...). Simultaneously deliver video and audio content. The transmission device 10 that transmits a data stream by IP multicast sets a multicast address in the IP address of the transmission destination, and transmits packets related to video and audio content. If the multicast address is IPv4 (Internet Protocol Version 4), addresses from “224.0.0.1” to “239.255.255.255” are used. In the case of IPv6 (Internet Protocol Version 6), an address in which the upper 8 bits of the address are all 1, for example, an address such as “FF00 :: 1” is used. Also, the network relay device that has received the IP multicast packet, that is, the router, receives an IGMP (Internet Group Management Protocol) JOIN request from each connected network to determine whether or not to transfer to another network. It is decided by whether or not.

  The IGMP JOIN request is a request for requesting the router to transfer an IP multicast packet, and designates a multicast address to request the transfer. The router transfers only the received packets whose designated destination is a multicast address. Also, the transfer of the IP multicast packet is stopped using an IGMP LEAVE request. The router that has received the LEAVE request stops forwarding the packet whose destination is the designated multicast address. If the router receives the same multiple IGMP JOIN requests from a single network, it receives a LEAVE request corresponding to the received JOIN request or transfers when the TIME-out of all JOIN requests has elapsed. Cancel.

  FIG. 6 is a flowchart and a sequence diagram showing processing in the receiving apparatus when video content is distributed by the IP multicast technology. In the present embodiment, the transmitting apparatus 10 uses the multicast address FF00 :: 1001 to transmit the MPEG2-TS data stream of channel N, and uses the FF00 :: 1002 to transmit the MPEG2-TS data stream of channel M. It is assumed that the relay device 20 is always distributed.

  As shown in FIG. 5 and FIG. 6, the receiving device 30a transmits a JOIN request to the multicast address FF00 :: 1001 to the relay device 20 after power-on (step 101, hereinafter, step is abbreviated as S). The relay device 20 receives the JOIN request and starts relaying the channel N to the receiving device 30a. When the MPEG2-TS data stream of channel N arrives, the receiving device 30a detects a TS packet with PID = 0, that is, a PAT from the data stream (S102). As described above, the PAT includes one or more PMT PIDs included in the data stream, and the receiving device 30a acquires the PMT PID from the PAT. The receiving device 30a detects the PMT from the data stream based on the PID of the PMT (S103). The receiving device 30a acquires the PID of the TS packet related to video and audio from the PMT, and sets the PID in the decoding unit 36 (S104). The decoding unit 36 extracts video data and audio data from the data stream based on the set PID of the TS packet related to video and audio, and starts reproduction of the video. When the video content is encrypted, the first acquisition unit 35-1 or the second acquisition unit 35-2 acquires the PID of the packet in which the ECM is further stored from the PMT, and the ECM from the data stream. May be detected, a decryption key may be generated based on the ECM data, and the content may be decrypted. When receiving the channel switching instruction (S105), the receiving device 30a transmits a LEAVE request for the multicast address FF00 :: 1001 to the relay device 20 (S106). After the relay device 20 stops transmission of the channel N by the LEAVE request, the receiving device 30a transmits a JOIN request for the multicast address FF00 :: 1002 to the relay device 20 (S107), and the PID of the packet relating to video and audio as described above Is acquired (S108 to S110).

<Function and operation>
FIG. 7 is a sequence diagram showing a flowchart of a control program at the time of channel switching according to the first embodiment and messages exchanged among the reception device, the relay device, and the transmission device. In the following, how the control program operates in the CPU 35 when the CPU performs channel switching will be described. In the present embodiment, as described above, it is assumed that the data streams of the channels M and N that can always be selected are distributed from the transmission device 10 to the relay device 20, and the relay device 20 receives the data from the reception device 30a. Whether or not to relay the data stream to the network 50 to which the receiving device 30a is connected is selected by an IGMP JOIN request and a LEAVE request. However, the data stream distributed by the transmission apparatus 10 corresponding to the channels M and N is not limited to the data stream, and is a data stream including at least one of a data packet related to video and a data packet related to audio. If it is good.

  As shown in FIGS. 5 and 7, when the power of the receiving device 30a is turned on, the control program is activated, and a channel is selected according to a predetermined rule to start video reproduction. For example, the channel immediately before the power was turned off last time is selected, and an IGMP JOIN request is sent to the relay apparatus 20. Hereinafter, the channel selected at this time is N.

  Specifically, information (distribution information) related to the data stream distributed from the transmission device 10 is acquired in advance by the distribution information acquisition unit 35-3 realized by the CPU 35 or the network connection unit 31 of the reception device 30a. The distribution information acquired by the distribution information acquisition unit 35-3 is stored in the RAM 32 or the ROM 33. Based on the distribution information, the reception device 30a receives the data stream at the reception unit 31-1 realized by the network connection unit 31, and the data stream is received by the first acquisition unit 35-1 realized by the CPU 35. Get program designation data from

  Next, a PID of encoded data related to video and audio is acquired from the program designation data by the first acquisition unit 35-1 realized by the CPU 35, and video and audio are acquired from the data stream based on the PID. The encoded data for is extracted. Then, encoded data related to the video and audio is extracted by the output unit realized by the decoding unit 36, the video data is output to the video decoding unit 36a, and the audio data is output to the audio decoding unit 36b. The data input to the video decoding unit 36a is decoded and output as video from the video display unit 37, and the data input to the audio decoding unit 36b is decoded and output as audio from the audio output unit 38.

  When the reproduction of the video of the first channel N is started, the CPU 35 selects a channel M different from the channel currently being reproduced, and transmits an IP cast JOIN request to the relay apparatus 20 (S201). The channel M is a channel determined by a predetermined rule, which is different from the channel N, and is a frequency band in which a data stream different from the data stream is distributed, or a port number. For example, the channel M may be a channel next to the channel currently being played back, or may be a channel most likely to be selected next predicted based on the user's past viewing history.

  The relay device 20 that has received the JOIN request from the receiving device 30a starts transferring the data stream of channel M. When the receiving apparatus confirms reception of the data stream of channel M (S202), it confirms the PID of each TS packet and detects PAT (PID = 0). If the PAT is detected, the PAT is analyzed, and the PID of the PMT included in the data stream is acquired (S203). If the PID of the PMT can be detected, the PMT is detected from the data stream and the PMT is analyzed. That is, the CPU 35 acquires the PID of the video and audio packet for the channel M, and stores (stores) the PID of the video and audio data packet in the RAM 32 (S204). That is, the CPU 35 stores the PID of the video and audio packets for the channel M that is not currently being output on the RAM 32.

  When the PAT includes PIDs of a plurality of PMTs, the CPU detects the plurality of PMTs from the data stream, and stores the PIDs of video and audio packets for each PMT in the RAM 32. . When the acquisition of the PID of the video and audio packets is completed, the receiving device 30a transmits an IGMP LEAVE request from the network connection unit 31 to the relay device 20, and stops the video transfer of the channel M from the relay device 20 ( S205).

  That is, the receiving device 30a according to the present embodiment extracts video data from one data stream and reproduces video while receiving two data streams, and video data and other data from the other data stream during the reproduction. The PID of the voice data packet is acquired. The PID detection processing of video and audio packets executed in S201 to S205 may be performed only for a predetermined channel based on the distribution information, or a channel that can be received by the receiving device 30a. (Data stream) may be detected, and the receivable channel (data stream) may be selected in order, and may be repeatedly executed for each channel (data stream). That is, the receiving device 30a receives a data stream including identification information of packets related to video data and audio data not yet acquired, and packets related to video data and audio data not yet acquired from the data stream. It is preferable to continue acquiring the identification information.

  When the user performs a channel switching operation using a remote controller or the like, the operation information is received by the remote control signal receiving unit 34. When the receiving unit realized by the remote control signal receiving unit 34 receives a channel switching instruction, it performs channel (data stream) switching processing. Specifically, the receiving device 30a stops the transfer of the channel N by transmitting an IGMP LEAVE request from the network connection unit 31 to the relay device 20 (S206). Then, the receiving device 30a transmits an IGMP JOIN request to the relay device 20 to start transfer of the channel M (S207). Then, the CPU 35 reads out the video and audio packet PID corresponding to the channel M designated by the switching support received by the remote control signal receiver 34 from the RAM 32 and sets it in the decoder 36 (S208). Based on the PID of the video and audio packets set in the decoding unit 36 and the data stream input to the decoding unit, reproduction of the video content is started.

  As described above, when the receiving device 30a of the present embodiment is used, even when there is no PID notification from the transmitting device 10 that is a content distribution source, when a channel switching instruction is issued, a packet related to video and audio is transmitted. By acquiring the PID stored in advance in the RAM 32 without performing the PID acquisition process, it is possible to immediately extract the video and audio from the data stream and start the reproduction process. In other words, in the state where one video is being played back, other data streams that have not yet arrived at the receiving device can be received and identification information regarding other video packets and audio packets can be acquired. Other videos can be played back based on the identification information acquired in advance, and the time from when the channel change instruction is received until the other videos start playing can be shortened. In other words, in the receiving device, it is possible to reduce the time from receiving an instruction to change video data or audio data to be output until other video data or audio data is output. In addition, it is possible to speed up the program switching by using the identification information acquired in advance.

  Further, in the present embodiment, unnecessary data transmission can be stopped after the prior acquisition of the identification information, so that it is possible to reduce network traffic without imposing an extra load on the network.

  Further, in the present embodiment, the case where the relay device 20 corresponding to the IP multicast is a broadband router has been described, but the relay device 20 is installed on the Internet or a device different from the broadband router on the LAN. It may be.

[Embodiment 2]
Hereinafter, the receiving device 30b according to Embodiment 2 will be described. The overall configuration of the network, the functional configuration of the receiving apparatus, and the hardware configuration are the same as those shown in FIGS. 3, 4, and 5 of the first embodiment. As shown in FIG. 3, the network 40 is the Internet, and the network 50 is a LAN. The relay device 20 is a broadband router, and connects the network 40 and the network 50 to each other. However, the relay apparatus 20 according to the present embodiment does not need to support the IP multicast function. The transmission device 10 is a video content distribution server, and transmits / stops a data stream using RTSP (Real Time Stream Protocol) recommended by RFC (Request For Comment) 2326. Then, the transmission apparatus 10 receives a request for transmission / stop of the data stream. That is, the data stream according to the present embodiment is not distributed to a plurality of receiving apparatuses at the same time, but is transmitted to each receiving apparatus in response to a request from each receiving apparatus.

  The receiving device 30b is a television capable of requesting transmission / stop of video content using RTSP and receiving / reproducing video content distributed via the networks 40 and 50.

  The configuration of receiving apparatus 30b is as shown in FIG. 4 as in the first embodiment. More specifically, since only the control program stored in the ROM 33 and executed by the CPU 204 is different from the receiving apparatus of the first embodiment, the description of the hardware configuration will not be repeated.

  Next, control when channel switching is performed after a predetermined time has elapsed after the control program is started will be described in detail with reference to a flowchart and a sequence diagram.

  FIG. 8 is a sequence diagram illustrating a flowchart of a control program at the time of channel switching according to the second embodiment and messages exchanged among the reception device, the relay device, and the transmission device.

  When the power of the receiving device 30b is turned on, the control program is activated, and the CPU 35 selects a channel according to a predetermined rule and starts playing a program (video). For example, the CPU 35 reads the channel immediately before the previous power-off, and sequentially transmits the RTSP DESCRIBE, SETUP, and PLAY requests to the transmitting device 10 via the network connection unit 31, thereby transmitting the data stream. Request. Hereinafter, the channel selected at this time is N.

  When the CPU 35 executes a control program stored in the ROM 33 in advance, the following processing and functions are realized. When the reproduction of the video is started, the CPU 35 selects a channel M different from the channel currently being reproduced, and sequentially sends an RTSP DESCRIBE, SETUP, and PLAY request to the transmission apparatus 10 (S301). The transmitting device 10 that has received each request transmits a response to each request to the receiving device 30b, and starts transmitting the data stream of the designated channel M after receiving the PLAY request.

When the transmission of the data stream is started, the PID of video and audio packets is detected from the data stream in S302 to S304. Each processing from S302 to S304 is the same as the processing from the embodiments S202 to S204, and description thereof will not be repeated here.
When the acquisition of the PID of the video and audio packets is completed, the reception device 30b transmits an RTSP STOP request to the transmission device 10 and stops the video transfer of the channel M from the transmission device 10 (S305).

  The video and audio packet PID detection processing executed in steps S301 to S305 may be performed only on a predetermined channel, or the reception device 30b can detect and receive the channel. The correct channels may be selected in order and repeated for each channel.

  When the remote control signal receiving unit 34 receives a channel switching instruction, the CPU 35 performs a channel switching process. An RTSP STOP request is transmitted to stop transmission of the channel N by the transmission apparatus 10 (S306), and an RTSP DESCRIBE, SETUP, and PLAY request are sequentially transmitted to cause the transmission apparatus 10 to start transfer of channel M ( S307). Thereafter, as in the first embodiment, the PID of the video and audio packets of the data stream corresponding to the designated channel M is read and set in the decoding unit 36 (S308), and the data stream is input to the decoding unit. To start playback of the specified channel.

  In the present embodiment, an example in which RTSP is used as a method for requesting a data stream has been shown. However, for example, HTTP (Hyper Text Transport Protocol) recommended by RFC 2616 can also be used.

  As described above, when the receiving apparatus according to the second embodiment is used, in the unicast video distribution service using RTSP or the like, even when there is no PID notification from the content server, The reproduction process can be started immediately without performing the video and audio PID detection process. That is, in the receiving apparatus, it is possible to reduce the time from when the video data or audio data to be output is changed to when other video data or audio data is output.

[Embodiment 3]
Hereinafter, the receiving apparatus according to Embodiment 3 of the present invention will be described. The present embodiment is different from the first embodiment in that the receiving device 30c can acquire a surplus bandwidth of the network between the relay device 20 and the receiving device 30c for transmission / reception of a data stream with the relay device 20. Different.

  FIG. 9 is a schematic diagram showing an embodiment of a LAN. For example, as shown in FIG. 9, when the network 50 is compliant with Ethernet (registered trademark) and includes a HUB, the reception of the surplus bandwidth by the receiving device 30c is performed on the network 50 on the HUB. And a method in which the relay device 20 and the receiving device 30c monitor network traffic in each network interface and notify the receiving device 30c.

  FIG. 10 is a schematic diagram showing another embodiment of the LAN. As shown in FIG. 10, when the network 50 is typically configured by a wireless LAN (IEEE802.11a / b / g), a wireless LAN AP (Access Point, in FIG. A method of monitoring wireless traffic and notifying the receiving device 30c is also conceivable.

  FIG. 11 is a schematic diagram showing another embodiment of the LAN. When the network 50 is compatible with a wireless LAN (IEEE 802.11e / n) as shown in FIG. 10 or QoS (Quality Of Service) constituting the network, such as PLC (Power Line Communication) as shown in FIG. Since the AP and coordinator manage the use status of the bandwidth of each device existing in the network, the surplus bandwidth is calculated by calculating the surplus bandwidth based on the management information and notifying the reception device 30c. It is possible.

  In the present embodiment, as in the first embodiment, it is assumed that a data stream of a selectable channel is always distributed from the transmission apparatus 10 to the relay apparatus 20, and the relay apparatus 20 transmits the IGMP data from the reception apparatus. It is assumed that it is determined whether or not to perform relay to the network to which the receiving device 30c is connected according to the request.

  Next, control when the control program performs channel switching will be described in detail using a flowchart. FIG. 12 is a sequence diagram illustrating a flowchart of a control program at the time of channel switching according to the third embodiment and messages exchanged among the reception device, the relay device, and the transmission device. Note that the processing for obtaining / stopping the data stream transfer to / from the relay device 20 and the process of obtaining the PID of the video data or audio data packet from the data stream by the receiving device 30c is the same as in the first embodiment. The explanation is not repeated.

  When the power of the receiving device 30c is turned on and the reproduction of the program corresponding to the channel N is started, the control program acquires the surplus bandwidth that can be used between the relay device 20 and the receiving device 30c (S401). If the surplus bandwidth can be obtained, the transmission bandwidth necessary for transmitting the data stream of channel M from which PID is to be obtained next is compared with the surplus bandwidth (S402).

  If the surplus bandwidth is equal to or greater than the required bandwidth Y (YES in S402), the PID of the video data and audio data packets is acquired in advance in S403. This processing corresponds to the processing from S201 to S205 in the first embodiment. When the pre-acquisition of PID is completed, it is determined whether or not a channel switching instruction is received from the remote control signal receiver 34 (S404).

  On the other hand, if it is determined in S402 that the surplus bandwidth is not equal to or greater than Y (NO in S402), it is determined whether a channel switching instruction has been received without performing prior acquisition of the PID. If it is determined that a channel switching instruction has been received (YES in S404), a stop request for the data stream of the channel N being reproduced and a start request for the designated channel M are transmitted (S405). For this, an IGMP LEAVE request and a JOIN request are used as in the first embodiment.

  Then, the CPU 35 determines whether or not the PID of the video and audio packets acquired in advance is stored in the RAM 32 (S406). If there is a PID of a video and audio packet acquired in advance (YES in S406), the CPU 35 reads the PID from the RAM 32, sets the PID for the decoding unit 36, and immediately switches to the channel M (S408). . If the PID acquired in advance is not stored in the RAM 32 (NO in S406), the PID of the video and audio packets is acquired from the data stream of the channel M (S407), and the acquired PID is set to decode. Switch channels immediately. At this time, the CPU 35 stores the acquired PID in the RAM 32.

  When the channel switching process is completed in S408, the process from S401 is repeated. However, the channel selected for executing the prior acquisition of the PID next time may be different from the previous channel. If it is determined in S404 that a channel switching instruction has not been received (NO in S404), the processing from S401 is repeated.

  As described above, the receiving apparatus according to the third embodiment executes the PID pre-acquisition process only when the excess bandwidth of the network is sufficient to flow the data stream to be pre-acquired. If the surplus bandwidth of the network is not sufficient, it may adversely affect the playback of the video of the currently selected channel and the user may feel uncomfortable. However, the receiving apparatus of this embodiment avoids such a situation. can do.

  Further, in the present embodiment, an example of distribution using IP multicast has been shown, but an example of distribution using unicast communication between a transmitting device and a receiving apparatus as in the second embodiment is also conceivable. In this case, as in the present embodiment, not only the communication state in the LAN but also means for the reception device 30c to acquire the network communication state in the relay device 20 from the transmission device 10 is necessary. For example, a method is conceivable in which a router existing between the transmission device 10 and the relay device 20 acquires the communication status, and the reception device 30c acquires the communication status.

  As described above, the receiving apparatus according to the present embodiment shortens the time from receiving an instruction to change the output video data and audio data to outputting other video data and audio data. be able to. In addition, when video and audio are being reproduced, it is possible to reduce the influence on transmission / reception of a data stream in which data relating to the video and audio currently being reproduced is stored.

[Embodiment 4]
Hereinafter, receiver 30d according to Embodiment 4 of the present invention will be described. The present embodiment is different in that data can be transferred based on the priority set for each data that the relay device 20 passes on the relay device. The setting of which packet is prioritized can be made, for example, by transmitting a message to the relay device 20 by the control program of the receiving device 30d. For example, the destination IP multicast address or the combination of the IP address and the port number determines which packet is to be prioritized.

  Further, in the present embodiment, as in the first embodiment, it is assumed that a data stream of a selectable channel is always distributed from the transmission device 10 to the relay device 20, and the relay device 20 receives the data. It is assumed that a determination is made as to whether or not to relay to the network 50 to which the receiving device 30d is connected based on an IGMP request from the device 30d.

  Next, control when channel switching is performed after the CPU is started will be described in detail with reference to flowcharts. FIG. 13 is a flowchart of a control program at the time of channel switching according to the fourth embodiment.

  When the power of the receiving device 30d is turned on and the reproduction of the program is started, the priority of the designated channel is set to a value greater than zero. Hereinafter, the priority set here is assumed to be Y. For example, the receiving device 30d notifies the relay device 20 to preferentially transfer the packet of the IP multicast address for distributing the data stream of the channel for which the transmission destination is specified, and starts playing the program.

  When playback of the program is started, channels other than the current playback are set to 0 (S501). Then, a channel X different from the channel N is selected (S502), a transfer request for the data stream of the channel X is made to the relay device 20, and PIDs of video and audio packets are acquired in advance (S503).

  When a channel switching instruction is received from the remote control signal receiver 34 (YES in S504), the priority of the designated channel is set to Y (S505), the channel is switched (S506), and the original channel is changed. The priority is set to 0 (S507). If the channel switching support is not received (NO in S504), it is determined whether or not PIDs of video and audio packets related to the data streams of all channels have been acquired in advance, and if not acquired (NO in S508). ), Specify the channel of the data stream for which the PID has not yet been acquired, and repeat the processing from S502.

  On the other hand, if the PIDs of all the channels have been acquired (NO in S508), it is determined whether or not the elapsed time since the last acquisition of PID is a predetermined time abnormality (S509). If the time elapses (YES in S509), the previously acquired PID is cleared and the processing from S502 is repeated. If the predetermined time has not elapsed (NO in S509), the process waits for the predetermined time to elapse while monitoring the channel switching instruction in S504. If the priority of the original channel is set to 0 in S507, the processing from S508 is performed in the same manner as when the channel switching instruction has not been received (NO in S504). In the present embodiment, the CPU 35 repeats the above processing (the processing after S509) while the power is on.

  As described above, the receiving apparatus according to the present embodiment assigns a high priority to a data stream for video reproduction in a network that can give priority to data (packet) transmission transmitted over the network. A low priority is set for a data stream used for automatic pre-acquisition of PID without video playback. If the data stream currently being played has a packet loss or transmission delay, video playback will be hindered. However, even if a large number of packet losses and transmission delays occur in the data stream for acquiring the PID in advance, Since PAT and PMT are distributed at intervals of several hundred msec to several sec, the time until prior acquisition is only slightly increased, and this is not a big problem. Therefore, it is possible to obtain the PID in advance without hindering the data stream distribution.

  In addition, the receiving apparatus according to the present embodiment performs pre-acquisition of PIDs of all channels, and after a predetermined time has elapsed, clears the pre-acquired PIDs once and acquires PIDs again. The video and audio PIDs included in the data stream are not always constant and may be changed. Even in such a case, it is possible to acquire a new PID by periodically re-executing the prior acquisition of the PID. In addition, when a channel change is performed while the pre-acquisition is completed after the PID is changed, an old incorrect PID may be set. In order to cope with such a case, after setting the PID acquired in advance and executing the playback of the video, the PID is acquired from the data stream being played back. A method of setting is conceivable.

  In the present embodiment, the receiving apparatus 30d has described the form in which the relay apparatus 20 is notified of which packet is prioritized or not. However, the transmitting apparatus 10 is not compatible with IEEE 802.1D Annex. The relay device 20 may have a function of assigning a priority specified by G, and the relay device 20 may transfer according to the priority assigned to each packet. In this case, which level of priority is set for which data is transmitted from the receiving device 30d to the transmitting device 10.

[Embodiment 5]
Hereinafter, the receiving apparatus according to Embodiment 5 of the present invention will be described. The overall system configuration is substantially the same as in the first embodiment. In the present embodiment, the communication medium has a bandwidth securing type QoS function that secures a bandwidth in response to a required bandwidth request from each device. As a communication medium, IEEE802.11e which is a wireless LAN standard, PLC which is a communication technology using a power line, COAX (COAXial network) which is a communication technology using a coaxial cable, and the like are used. The receiving device 30e requests a necessary band when starting transmission of a data stream to a communication medium that configures a network. For example, in the case of a PLC network as shown in FIG. 11, a bandwidth securing request is made to the coordinator.

  Further, in the present embodiment, as in the first embodiment, it is assumed that data streams of channels M, N,... That can be always selected are distributed from the transmission apparatus 10 to the relay apparatus 20, and the relay is performed. It is assumed that the device 20 determines whether to perform relay to the network 40 (LAN) to which the receiving device 30e is connected in response to an IGMP request from the receiving device 30e.

  Next, control when the CPU 35 switches from one channel to another after the control program is started will be described in detail with reference to a flowchart. FIG. 14 is a flowchart of a control program at the time of channel switching according to the fifth embodiment.

  When the power is turned on, the receiving device 30e acquires a program table (program table) (S601). In the present embodiment, a dedicated channel for transmitting the program guide is prepared, and the program guide data is obtained by executing IGMP JOIN on the dedicated channel. That is, the program table is a program table in which program information corresponding to a plurality of different data streams is stored.

  If the program guide is acquired, the communication medium is requested to secure a transmission band for a channel for reproducing video (S602). For example, HD (High-Definition) MPEG2 requires a transmission rate of about 24 Mbps. In order to obtain PID in advance, a plurality of bandwidths having a transmission rate smaller than 24 Mbps are requested. For example, if there are 10 channels that can be selected, 10 channels are secured at 2 Mbps (S603).

  When the transmission band can be secured, IGMP JOIN is transmitted to the relay device 20, a data stream transfer is requested, and video reproduction is started (S604). Then, based on each program information stored in the acquired program guide, the other channels (data streams) are requested to start transmission using a bandwidth of 2 Mbps (S605). Then, the video and audio PID of each channel is acquired in advance from each data stream (S606).

  Then, it is determined whether a channel switching instruction has been received from the remote control signal receiving unit 34 (S607). If it is determined that a switching instruction has been received (YES in S607), the band used in the currently playing stream and the next selection are selected. The channel switching process is executed by exchanging the band used for the selected channel (S608). When the channel switching is completed, the program information is confirmed from the program table acquired in S601, and it is determined whether or not the program switching time has come (S609).

  When the program switching time is reached (YES in S609), the process returns to S606, and the PID of the switched channel is acquired. If it is not the program switching time (NO in S609), the process returns to S607 to check whether a channel switching instruction has been received or not, and waits until the program switching time is reached. If no channel switching instruction has been received (NO in S607), the process of S609 is executed. In the present embodiment, the CPU 35 repeats the above processing (the processing after S609) while the power is on.

  As described above, the receiving apparatus according to the present embodiment performs playback in a network configured by a communication medium having a bandwidth securing type QoS function for securing a bandwidth in response to a required bandwidth request from each device. A sufficient transmission band for video transmission is allocated to the data stream, and a small band is allocated to the data stream to be acquired in advance, and the PID is acquired in advance.

  The data stream to be reproduced adversely affects video and audio when packet loss or arrival delay occurs. However, as described in the fifth embodiment, the data stream for pre-acquisition of PID is large. It doesn't matter. Moreover, if a large number of bands are allocated to a data stream for pre-acquisition of PID, the use band of other network connection devices is compressed, which causes a disadvantage to the user. Such a problem can be solved by allocating a small transmission band to the data stream for pre-acquisition of PID.

  In addition, the receiving device 30e according to the present embodiment updates the PID at the timing of switching programs by acquiring the program guide. In other words, the receiving device 30e receives a program table receiving unit that receives a program table storing program information corresponding to a plurality of different data streams (channels M, N...) Via the networks 40 and 50. 35-5, and the request unit 35-4 requests the transmission apparatus 10 to transmit the second data stream based on each program information stored in the acquired program table.

As described in the fifth embodiment, the program and the data stream are not always constant and may be changed. However, in the present embodiment, even when the identification information acquired in advance becomes invalid with the passage of time, the client device can automatically acquire the second identification information again.
By using the information of the program guide, it becomes possible to perform efficient reacquisition.

[Embodiment 6]
Hereinafter, the receiving device 30f according to the sixth embodiment of the present invention will be described. The diagram showing the system configuration is substantially the same as in the first embodiment. In this embodiment, video data is encrypted and transmitted, and an ECM packet necessary for generating a key for decryption is included in the MPEG2-TS stream.

  Next, the control when another channel is switched after the control program is started will be described in detail with reference to a flowchart. FIG. 15 is a flowchart of the control program at the time of channel switching according to the present embodiment.

  When the power of the receiving device 30f is turned on, reproduction of a predetermined channel N is started (S701), and a transmission request for other channels is issued (S702). Then, in addition to the video and audio packet PID, the ECM PID is also acquired from the data stream of each channel (S703). The ECM PID can be acquired from the PMT in the same manner as the PID of video and audio packets. Then, an ECM packet is acquired and a decryption key is generated based on the ECM (S704). The decryption key is generated using, for example, CAS (Conditional Access Systems) technology. If a channel switching instruction is issued from the remote control signal receiving unit 34 (YES in S705), the channel switching is executed. More specifically, the content is decrypted and reproduced using the decryption key generated in advance (S706). If there is no instruction to switch channels (NO in S705), the processing from S703 is repeated. In the present embodiment, the CPU 35 repeats the above process while the power is on.

  As described above, the receiving apparatus according to the present embodiment acquires not only video and audio packet PIDs but also ECM PIDs, and generates a decryption key in advance. Since it takes time to generate the decryption key, it is possible to speed up the video switching at the time of channel switching by using the decryption key generated in advance. In other words, in the case of a transmission method in which it is necessary to extract information necessary for encryption from multiplexed data and generate a decryption key, video and audio of a new channel are displayed after receiving a channel change instruction. The time until is shortened.

[Modifications of Embodiments 1 to 6]
In the first to sixth embodiments, an example in which PID is acquired in advance during reception / playback of a predetermined data stream has been described. For example, PID is acquired in advance while the receiving apparatus is in a standby state. Various configurations are also conceivable. In other words, the request unit 35-4 also includes the distribution information in the period when the decoding unit 36 stops extracting and outputting video data and audio data from the channel N (first data stream). Based on this, the transmission apparatus 10 is requested to transmit the channel M or the like (a plurality of data streams). The second acquisition unit 35-2 also receives the PID (the first ID) of the video and audio packets from the channel M and the like during the period when the extraction and output of the video data and audio data from the channel N are stopped. 2 identification information). And the memory | storage part 32-1 implement | achieved by the said RAM32 memorize | stores PID (2nd identification information) of video and audio | voice packets, such as the said channel M, also in the said period, In this case, immediately after power activation In addition, based on the PID acquired in advance, not only the time of channel switching but also the response time after power-on can be improved.

  In the first to sixth embodiments, the receiving device 30f sends a stream transmission request for pre-acquisition of PID. For example, an IP multicast stream requested by another receiving device exists on the network. In this case, the PID may be acquired in advance by analyzing the IP multicast packet without making a transmission request.

  In addition, the receiving device 30f according to the first to sixth embodiments includes the video display unit 37 and the audio output unit 38, and the received data stream can be reproduced. However, the receiving device 30f displays the video. The structure which does not have the part 37 and the audio | voice output part 38 may be sufficient. For example, the receiving device 30f is a tuner device or a hard disk recorder compatible with the network, and an example in which the analog / digital output of the receiving device 30f is input to another video display device to reproduce the video is also conceivable.

  The above-described modifications can be combined with each other without changing the essence, and can be applied to other embodiments.

[Embodiment 7]
The receiving device 30 according to the first to sixth embodiments has been described with respect to the transmission device 10 and the relay device 20 that make a data stream transmission request, but the receiving device 30 does not actively make a transmission request. There may be. Below, when the transmission apparatus 10 is a broadcasting apparatus that broadcasts a television broadcast or the like, a suitable receiving apparatus 30g will be described.

  The receiving device 30g receives a data stream that is broadcast from at least one broadcasting device 10b and that includes at least one of video data and audio data and identification information for identifying at least one of the video data and audio data. It is a television or hard disk recorder having a tuner.

  As shown in FIG. 4, the receiving device 30g broadcasts from the broadcasting device 10b based on the distribution information acquiring unit 35-3 that acquires broadcasting information related to a data stream that can be broadcast by the broadcasting device 10b. Receiving unit 31-1 for receiving a plurality of data streams including the first and second data streams, and a first acquisition unit 35-1 for acquiring first identification information from the first data stream, , Based on the first identification information, an output unit 38-1 for extracting and outputting at least one of video data and audio data from the first data stream; and the receiving device 30g outputs the first data stream. During reception, the second acquisition unit 35-2 that acquires second identification information from the second data stream, and the reception device 30g include the first data stream. Storage unit 32-1 for storing each of the second identification information and reception unit 34- for receiving selection of the data stream including video data and audio data output from the output unit 38-1. 1.

  And when the said 2nd data stream is selected, the said output part 38-1 will start from the said 2nd data stream based on the said 2nd identification information memorize | stored in the said memory | storage part 32-1. At least one of video data and audio data is extracted and output.

  Also in this embodiment, other video can be played based on the identification information acquired in advance when the channel change instruction is received, and the other video is played after receiving the channel change instruction. Time to start can be shortened. Alternatively, the receiving device 30g may have the following configuration.

[Modification of Embodiment 7]
That is, when the acquisition of the second identification information is completed, the second acquisition unit 35-2 acquires identification information that has not yet been acquired from a data stream different from the first and second data streams. Is. This increases the types of identification information acquired in advance, increases the possibility that other videos can be played back based on the identification information acquired in advance when a channel change instruction is received. The time from when the video is received until another video starts to be played can be shortened.

  The above-described modifications can be combined with each other without changing the essence, and can be applied to other embodiments.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a conceptual diagram which shows the TS packet which comprises a data stream. It is a conceptual diagram which shows the data stream comprised from several TS packet. It is the schematic which shows the whole structure of a data stream transmission / reception system. It is a functional block diagram which shows the whole structure of a receiver. It is a figure which shows the hardware constitutions at the time of implement | achieving a receiver using CPU. It is the flowchart and sequence diagram which show the process in the receiver in the case of distributing a video content by IP multicast technique. FIG. 6 is a sequence diagram illustrating a flowchart of a control program at the time of channel switching according to the first embodiment and messages exchanged among the receiving device, the relay device, and the transmitting device according to the first embodiment. FIG. 9 is a sequence diagram illustrating a flowchart of a control program at the time of channel switching according to the second embodiment and messages exchanged among the receiving device, the relay device, and the transmitting device according to the second embodiment. It is the schematic which shows the Example of LAN. It is the schematic which shows another Example of LAN. It is the schematic which shows another Example of LAN. FIG. 10 is a sequence diagram illustrating a flowchart of a control program at the time of channel switching according to a third embodiment and messages exchanged among a receiving device, a relay device, and a transmitting device according to a third embodiment. 10 is a flowchart of a control program at the time of channel switching according to the fourth embodiment. 14 is a flowchart of a control program at the time of channel switching according to the fifth embodiment. 18 is a flowchart of a control program at the time of channel switching according to the sixth embodiment.

Explanation of symbols

  1 data stream transmission / reception system, 10 transmission device, 20 relay device, 31 network connection unit, 31 reception unit, 32 RAM, 33 ROM, 34 remote control signal reception unit, 35 CPU, 36 decoding unit, 36a video decoding unit, 36b audio decoding Unit, 37 video display unit, 38 audio output unit, 39 multiplexing division unit, 40, 50 network.

Claims (21)

A receiving device for receiving a data stream including at least one of video data and audio data and identification information for identifying at least one of the video data and audio data from a transmission device via a network,
Receiving means for receiving a plurality of data streams including first and second data streams from the transmitting device;
First acquisition means for acquiring first identification information from the first data stream;
Output means for extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information;
Second acquisition means for acquiring second identification information from the second data stream while the receiving device is receiving the first data stream;
Storage means for storing the second identification information while the receiving device is receiving the first data stream;
Receiving means for receiving selection of the data stream including video data and audio data output by the output means,
When the second data stream is selected, the output unit selects at least one of video data and audio data from the second data stream based on the second identification information stored in the storage unit. Receiving device that extracts and outputs. The transmitter is
The receiving apparatus according to claim 1, wherein the receiving apparatus is a relay apparatus for transmitting a data stream received from another transmitting apparatus to the receiving apparatus.   The receiving apparatus according to claim 1, further comprising a reproducing unit that decodes at least one of the video data and the audio data extracted by the extracting unit to reproduce at least one of the video and the audio.   The receiving apparatus according to claim 1, further comprising request means for requesting the transmitting apparatus to transmit the second data stream. The request means requests the transmission device to transmit a plurality of different second data streams,
The receiving means receives the plurality of different second data streams transmitted from a transmitting device;
The second acquisition means acquires the respective second identification information from the plurality of different second data streams while the receiving device is receiving the first data stream,
The receiving device according to claim 4, wherein the storage unit stores the respective second identification information while the receiving device is receiving the first data stream.   When the acquisition of the second identification information is completed, the request unit requests the transmission device to stop transmitting the second data stream, and the request unit includes another data stream including the identification information that has not yet been acquired. The receiving device according to claim 4 or 5, which requests transmission. The request means requests the transmission apparatus to transmit a plurality of data streams even during a period in which the output means stops extracting video data and audio data from the first data stream.
The second acquisition means acquires second identification information from the second data stream during the period,
The receiving device according to claim 4, wherein the storage unit stores the second identification information even during the period.   The request unit according to any one of claims 4 to 7, wherein the request unit determines whether or not to transmit a message requesting transmission of the second data stream according to a load state of a network to which the receiving apparatus is connected. The receiving device according to claim 1. The receiving device is connected to the transmitting device via a network that can specify the transmission priority of data to be transmitted,
The receiving device according to claim 4, wherein the request unit designates the second data stream with a transmission priority lower than that of the first data stream. The receiving device is connected to the transmitting device via a network capable of designating a transmission band used for data transmission / reception,
10. The request unit according to claim 4, wherein the request unit designates a transmission band used for transmitting the second data stream as a transmission band narrower than a transmission band used for transmitting the first data stream. The receiving device according to claim 1.   The receiving device according to any one of claims 4 to 10, wherein the request unit transmits a message requesting transmission of the second data stream at a predetermined time interval. A program table receiving means for receiving a program table storing program information corresponding to a plurality of different data streams via a network;
The said request | requirement means requests | requires transmission of the said 2nd data stream from the said transmission apparatus based on each program information stored in the acquired said program table, The any one of Claim 4 to 11 Receiver. The data stream includes composite key generation information for generating a decryption key for decrypting at least one of encrypted video data and encrypted audio data,
Third acquisition means for acquiring the composite key generation information from the data stream;
The reception device according to claim 1, further comprising: a decryption key generation unit configured to generate the decryption key from the composite key generation information.   The receiving apparatus according to claim 13, wherein the composite key generation information is an ECM (Entitlement Control Message). The data stream is MPEG2-TS (Moving Picture Experts Group 2-Transport Stream) data,
The data stream includes a PAT (Program Association Table) and a PMT (Program Mapped Table),
The receiving apparatus according to claim 1, wherein the identification information includes at least one PID (Program ID) of video data and audio data. Further comprising distribution information acquisition means for acquiring distribution information relating to a data stream that can be distributed by the transmission device;
The receiving device according to any one of claims 1 to 15, wherein the receiving unit receives a plurality of data streams including first and second data streams from the transmitting device based on the distribution information. A receiving method using a receiving device that receives a data stream including at least one of video data and audio data and identification information for identifying at least one of the video data and audio data from a transmitting device via a network There,
Receiving a plurality of data streams including first and second data streams from the transmitting device;
Obtaining first identification information from the first data stream;
Extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information;
Obtaining second identification information from the second data stream while the receiving device is receiving the first data stream;
Storing said respective second identification information while said receiving device is receiving a first data stream;
Receiving a selection of the data stream including video data and audio data to be output;
When the second data stream is selected, at least one of video data and audio data is extracted from the second data stream and output based on the second identification information stored in the storage means And a receiving method. Requesting the transmitter to transmit a data stream;
The reception method according to claim 17, further comprising requesting transmission of another data stream including identification information that has not yet been acquired when acquisition of the second identification information is completed. A program for causing a computer connectable to a transmission device via a network to receive a data stream comprising at least one of video data and audio data and identification information for identifying at least one of the video data and audio data There,
Receiving a plurality of data streams including first and second data streams from the transmitting device;
Obtaining first identification information from the first data stream;
Extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information;
Obtaining second identification information from the second data stream while the receiving device is receiving the first data stream;
Storing said respective second identification information while said receiving device is receiving a first data stream;
Receiving a selection of the data stream including video data and audio data to be output;
When the second data stream is selected, at least one of video data and audio data is extracted from the second data stream and output based on the second identification information stored in the storage means And a program for causing a computer to execute the step. A data stream transmission / reception comprising: a transmission device; and a reception device that receives a data stream including at least one of video data and audio data and identification information for identifying at least one of the video data and audio data from the transmission device A system,
The receiving device is:
Receiving means for receiving a plurality of data streams including first and second data streams from the transmitting device;
First acquisition means for acquiring first identification information from the first data stream;
Output means for extracting and outputting at least one of video data and audio data from the first data stream based on the first identification information;
Second acquisition means for acquiring second identification information from the second data stream while the receiving device is receiving the first data stream;
Storage means for storing the respective second identification information while the receiving device is receiving the first data stream;
Receiving means for receiving selection of the data stream including video data and audio data output by the output means,
When the second data stream is selected, the output unit selects at least one of video data and audio data from the second data stream based on the second identification information stored in the storage unit. Data stream transmission / reception system that extracts and outputs data. The receiving device is:
Requesting means for requesting the transmitting device to transmit a data stream;
21. The data stream transmission / reception system according to claim 20, wherein when the acquisition of the second identification information is completed, the request unit requests transmission of another data stream including identification information that has not yet been acquired.

Images