JPH1188856A - Transmission protocol converting system and catv network connecting system using protocol converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce operation costs by commonly utilizing program contents by transmitting MPEG(Moving Picture Experts Group) video signals while mutually connecting CATV networks more than two through a network using an internet protocol by an interwork means. SOLUTION: Concerning an MPEG-transport stream(TS), the case of transmitting a payload for storing data continuously to a TS header 1 of 4 bytes and the case of transmitting an adaptation field 2 before the payload are allowed. When transmitting a signal to an IP network, concerning the TS to transmit an IP header, the adaptation field 2 is inserted just after a TS header without fail and while using this adaptation field 2, the IP header is transmitted. The adaptation field 2 stores a flag 4 of 2 bytes showing contents to be transmitted and private data 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for transmitting an MPEG image using an Internet protocol and a system thereof, and more particularly, to a network using a transmission system conversion device for rapidly converting between an MPEG transmission protocol and the Internet protocol. The present invention relates to a connection method and an encapsulation method of MPEG data to be transmitted.

[0002]

2. Description of the Related Art "GENERICCODING OF MOVING" is an international standard for digitally encoding and transmitting video.
PICTURES AND ASSOCIATED AUDIO: SYSTEMS "
IEC13818-1, ITU-T (International Tel
ecommunication Union) H. It is specified as a 222.0 recommendation. The MPEG System International Standard (hereinafter abbreviated as H.222.0) defines a standard for transmitting image signals compressed by the MPEG system.
H. 222.0 describes a program stream (hereinafter abbreviated as PS) format assuming transmission from a storage medium or the like in which bit errors are relatively less likely to occur, and a transport assuming a communication line where transmission bit errors are expected to occur. Two types of streams (hereinafter, abbreviated as TS) are defined.

[0003] The present invention is directed to a code conversion system for transmitting a compressed video signal in the TS format.
A description will be given of a conventional technique for an image transmission system using the S format. In the MPEG system for video / audio coding and transmission, an input video signal of a television or the like is digitized, and the digital signal is subjected to data compression using a technique such as discrete cosine transform or variable length coding. . Regarding audio signals, the method is different but digitized,
Compression is performed by removing redundant data. These compressed signals are called elementary streams (hereinafter abbreviated as ES), and are data which are elements of image / audio signals as the words imply. Note that M
In the PEG, this image / audio data is represented using the term (bit) stream.

[0004] In a cable television, a satellite communication line, or an asynchronous transfer mode transmission line (hereinafter abbreviated as an ATM line) for transmitting an MPEG video signal, it is assumed that a relatively large number of bit errors occur during data transmission. To reduce the range of the transmission of errors due to transmission errors.
S is divided into small packets and transmitted. The packetized ES is called a packetized elementary stream (hereinafter abbreviated as PES), and has a format in which header information called a PES header is added to the ES. In the transmission of the communication line exemplified above, this P
The ES is further divided into 188-byte packets called transport packets and transmitted. The TS packet is a packet composed of a 4-byte header and a 184-byte payload for storing data, as shown in FIG. FIG. 14 is a diagram showing a header structure of a TS packet. The TS header includes a 1-byte synchronization byte (0x47), a flag indicating the attribute of the TS packet (the content of each flag is omitted because it is not important in this description), and a 13-bit packet identifier (hereinafter, PID and Abbreviated), a scramble control identifier, an adaptation field identifier, and a 4-bit cyclic counter used to check the continuity of the packet. In the transport stream, a field called an adaptation field can be transmitted prior to a data field called a payload for storing video data. This field contains a program clock reference (hereinafter referred to as a PCR clock) for the purpose of system clock synchronization. ) And private data. When the adaptation field is transmitted in the TS packet, it is specified that the adaptation field is indicated by the adaptation field identifier of the TS header.

[0005] The MPEG system is a system developed for CATV and digital satellite broadcasting. Recently, a service using MPEG images has been developed even in a network called the Internet, which has been developed mainly for computer data communication. Is being offered.
The Internet Engineering Task Force (hereinafter referred to as IETF)
The standard of the MPEG image transmission format is Request for Comment N0. 2038:
A transmission method and a packet encapsulation method are standardized by “RTP Payload Format for MPEG1 / MPEG2 Video” (hereinafter abbreviated as RFC2038). RFC20
38, the format of the packet to be transmitted is MP
"RTP: A Transpo" specified by RFC1889 to transmit using EG ES, TS, or PS, and to avoid image quality degradation due to delivery delay
rt Protocol for Real-Time Applications ”(hereinafter R
(Abbreviated as TP). The RTP packet is stored in a packet according to a user datagram protocol (hereinafter abbreviated as UDP),
Further, it specifies that the UDP packet is transmitted by an Internet protocol packet (hereinafter abbreviated as an IP packet). According to the above-described conventional technology, MP-TS packets are used inside a CATV line and IP packets inside the Internet.
EG video can be transmitted.

[0006]

As described above, digital satellite broadcasting and a digital CATV system perform video transmission according to the MPEG-TS system. Among these services, the digital CATV system is a community-based service and a relatively small area is generally configured as a service providing area. Therefore, each CATV operator has a CATV center (hereinafter abbreviated as a head end) for transmitting a program and an access network for transmitting video, and retransmits terrestrial / satellite broadcast programs received at the head end. Or send programs stored in the headend as needed. In such a conventional CATV service, a program other than a broadcasted program needs to be stored in, for example, a VTR or the like and reproduced according to the program composition. Video-on-demand, etc., which is expected as a CATV service in the near future, is generally constructed in a format in which a digital compressed signal of a program is held at the head end in the same manner as described above. By the way, in the video-on-demand service, costs for maintaining services such as purchasing rebroadcasting rights (copyrights), digital compression processing of programs, and storage of compressed images in order to retain the program contents are high. There is a problem that profit cannot be obtained unless the number of accesses to the content) is increased. In order to solve this problem, for example, a method is effective in which a plurality of CATV companies jointly hold contents and transmit and use the contents when necessary using a communication line.

To construct such a system, a plurality of
It is necessary to connect the head end and network of CATV operators using communication lines. For example, in order to connect a US CATV headend to a set-top terminal (hereinafter abbreviated as STB) which is a video receiver of a Japanese CATV subscriber, at least a communication line between the US and Japan is used. Must connect. However, at present, MPEG-T generally used in digital CATV is used.
It is not realistic to transmit S in the same format.
That is, in the video transmission of MPEG-TS, there is a problem that a dedicated communication line such as an ATM line or a satellite line must be used, and the dedicated line has a high communication fee. In addition, since it is a dedicated line, it is assumed that the contract point is always connected and used. If it is used for services that occupy the network at the request of the user, such as on-demand services, cost performance is low. There is a big problem in this regard.

[0008]

In order to solve the above-mentioned problems, the present invention uses means for connecting a plurality of CATV networks via the Internet. The Internet is a network spread all over the world, and has a feature that a connection can be dynamically changed by an address assigned to each terminal or host computer. Therefore, there is no need to fix the connection point in advance, and the connection is made using the address when the video is to be distributed. Therefore, it is possible to perform free connection setting that cannot be realized with a dedicated line and low-cost video communication. In the current Internet, there is a problem that the transmission bandwidth is narrow, but the gigabit router and the bandwidth reservation protocol (Resource reservation setup Protocol
(l: RSVP), etc., to secure a transmission band, band shortage will not become a problem in the near future, and it can be easily expected that a global network environment will be realized by the Internet.

Further, as described above, a new problem occurs when connecting a CATV network using the Internet: "A protocol conversion between the MPEG transmission protocol used in the CATV network and the IP protocol used in the Internet is necessary. In the present invention, the problem is solved by providing an interwork unit that converts between the MPEG-TS protocol and the Internet protocol. In order to solve the problem that the processing speed and cost must be reduced in this interworking unit, it is necessary to provide a means for improving the configuration method and the conversion method of a packet transmitted in an MPEG network or an IP network. Solved by.

[0010] Specifically, 1) a header of an IP packet is stored in a private data area of an adaptation field specified by the MPEG-TS system and transmitted;
In the internetwork unit, a packet for transmitting the inside of the Internet as a header of the IP packet without analyzing the private data in the adaptation area without any analysis. 2) When transmitting the MPEG video signal from the Internet, the IP packet to be transmitted is used. When the size is divided into MPEG-TSs, there is adopted a method in which a restriction condition of a size that can be accommodated in the payload is provided and transmitted.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First Embodiment FIG. 9 is an embodiment showing a connection form of a CATV system according to the present invention. This CATV system has two C
It is characterized in that the ATV networks 61 and 56 are connected via the Internet 50. As shown in the figure, the CATV system includes a video server 60 and a CATV connected thereto.
A network 61, the Internet 50, an internetwork unit 62 for connecting the Internet 50 to the CATV network 61, a second CATV network 56, and the network 56 and the Internet 50;
Are connected by an interwork unit 54. C
The ATV network 56 has an S for receiving video.
TB57 is connected. The video signal from the video server 60 is transmitted to the Internet 50 via the interwork unit 62, and is delivered to the interwork unit 54 by a router network. The interworking unit 54 supplies a video signal transmitted using the Internet to the CATV network 56, thereby enabling the STB 57 to receive video.

Here, the function of the interworking unit will be briefly described. In the CATV network, a video signal is transmitted by the MPEG-TS method as described in the section of the related art. On the other hand, in the Internet, image transmission is performed by an Internet protocol represented by RFC2038. Interworking unit 6 for interconnecting networks using different protocols
No. 2 has a function of converting from the MPEG-TS protocol to a signal format conforming to the Internet protocol. On the other hand, the interwork unit 54 has a function of converting an image signal transmitted according to the Internet protocol into an MPEG-TS protocol. By connecting different CATV networks via the Internet using such interwork units 62 and 54, an unprecedented function such as easy connection between a CATV video server that is far away and an STB is realized. it can. The Internet is a network developed all over the world. According to this configuration, an enormous effect can be obtained such that connectivity between the video server and the STB worldwide can be secured.

In the embodiment of FIG. 9, a video server is described as an example of a device for generating a video signal. However, the gist of the present invention is to deliver a video signal supplied by the MPEG protocol via the Internet. The signal source is not limited to the video server. As a device for supplying an MPEG signal to a device other than a video server, there are a real-time MPEG encoder and a receiving facility for receiving a satellite broadcast and outputting an MPEG signal. Even with these devices, the purpose of the present invention is satisfied. Needless to say.

Further, in this embodiment, an example in which two different CATV networks are interconnected for simplicity has been described, but it is needless to say that more than two CATV systems may be connected to the Internet. Not reachable.
The gist of the present invention is that the MP
A signal transmitted by the EG-TS system is converted into a format that can be transmitted via the Internet, and the converted video signal is transmitted via the Internet.
The point is that the signal is converted into a PEG-TS signal and transmitted to a CATV network.

Second Embodiment In the second embodiment, in addition to the CATV connection via the Internet described in the first embodiment, video transmission from a server on the Internet to the STB on the CATV, video on the CATV A method for converting a shared video transmission protocol that also takes into account video transmission from a server to a client PC on the Internet and a protocol between different networks is disclosed.

FIG. 8 shows the video transmission from the video server 55 on the CATV to the client 4 on the Internet, and the transmission from the server 52 on the Internet to the S on the CATV network.
It is a connection diagram of the network structure which enables both the video transmission of TB57.

First, a case where an image is transmitted from the video server 55 connected to the CATV network 56 to the client 4 on the Internet will be described. Note that packetization and protocol conversion when video is transmitted from a server on the Internet to an STU on a CATV network will be described in detail in a fourth embodiment.

When video is transmitted from the video server 55 to the client 4, the video server 55 transmits video using the packet configuration shown in FIG. This video signal is
The TV network 56 reaches the interwork unit 62 according to the MPEG-TS scheme. The internetwork unit 62 converts the video signal carried by the MPEG-TS into a packet that can be transmitted by the Internet protocol by a conversion method described later, and converts the video signal into a packet that can be transmitted by the Internet.
Send to 1. In the Internet 51, the video signal is delivered to the client 4 using the IP protocol. In addition,
This signal can be sent to the interworking unit 54 in the same manner as sent to the client 4. In the interconnection of the CATV network, the interwork unit 54 converts the protocol to MPEG-TS again.

Here, the packet encapsulation method shown in FIG. 1 will be described in detail. FIG. 1 shows an STB 57 connected to the Internet 50 and a CATV network 56 from the video server 55 of FIG.
ST on another CATV network connected via
4 is an embodiment showing a configuration of an MPEG-TS signal transmitted to B. In MPEG-TS, transmission of a payload storing data following transmission of a 4-byte TS header 1 and transmission of an adaptation field 2 prior to the payload are permitted. In the present invention, I
When transmitting a signal to the P network, as shown in FIG. 1, in a TS transmitting an IP header, an adaptation field 2 is always inserted immediately after the TS header, and the IP header is transmitted using the adaptation field 2. . The adaptation field 2 stores a 2-byte flag 4 indicating the content of data to be transmitted, and private data 5. To transmit the private data 5, the flag (transport_private_data_flag) indicating the contents of the adaptation field indicates that the private data 5 is to be transmitted, and the size of the private data 5 is included in the flag as the private data length (transport_private_data_length). Set as As this private data 5, the 20-byte IP packet header 6 is stored as it is in the bit array. FIG. 7 shows the I stored in the private data 5.
FIG. 3 is a diagram showing the contents of a P packet. The IP packet header has a 4-bit field indicating a version, a header length, a service type, a total packet length, an identifier and a transmission source I.
It is composed of a P address and a destination IP address. If there is no option, it is composed of 20 bytes. Since options are not used under general conditions, data including a 20-byte field is stored in the private data area and transmitted as it is.

The data of the TS is stored in the PES format following the adaptation field. The reason for transmitting the video signal in the PES format will be described later.

In the embodiment of FIG. 1, an example is shown in which private data is transmitted including only an IP packet header. However, according to a protocol supported by a terminal (client) connected to the IP network, a UDP header,
Alternatively, a format including both a UDP header and an RTP header may be used. FIG. 2 shows an embodiment in which a UDP header is accommodated following an IP header as private data, and FIG. 3 shows an embodiment in which an IP header, a UDP header and an RTP header are transmitted as private data. A feature of the present invention is that data of a packet header of a protocol used in an IP network is transmitted as private data, and the present invention is not particularly limited to protocols such as UDP and RTP. At present, the use of RTP is most effective for transmitting real-time video signals over the Internet, so the packet configuration shown in FIG. 4 is the best. Further, in the embodiments of FIGS. 1, 2 and 3, the case where the IP header, the UDP header, and the RTP header are directly transmitted as private data has been described. Of course, it is also possible to transform and transmit as private data. However, in this case, it is necessary to perform a process of reconstructing an IP header or the like based on the data transmitted in the interwork unit, so that it is easily understood that transmission in the same format is most effective. .

Here, the reason why PES is used as a data format will be briefly described. As shown in FIG. 8, the video server 55 is an STB 57 connected to the CATV network.
The video is also transmitted to. It is preferable to share the video transmitted to the Internet 50 and the video transmitted to the STB 57 from the viewpoint of reducing data creation cost and system cost, and it is most suitable to adopt the PES format used in the conventional CATV. . The information of the IP header encapsulated in the adaptation field is
Since it is processed separately from the audio signal, it does not affect the video reproduction of the conventional STB 57 at all. By using the PES format, it is possible to transmit a video signal to an IP network while maintaining signal compatibility with a conventional STB. Although the PES format is not specified in RFC2038, since the PES has a configuration in which an ES is divided into a plurality of packets and a PES header is added, the PES can be easily converted to the ES. Therefore, a client that can receive and decrypt an ES can decrypt it with almost no additional functions.

Here, a supplementary method of configuring the IP packet will be described. Maximum size of Ethernet IP packet (Ma
ximum Transfer Unit size) is 1500 bytes. Therefore, a maximum of seven 184-byte payloads of MPEG-TS can be packed. Therefore, when transmitting a TS packet, a TS packet including an IP header is transmitted at a period of 7 TS. The interworking unit receives the packet including the IP header and constructs the IP header as conceptually shown in FIG. 6, and then connects the data of the payload of the subsequently transmitted TS packet to generate the IP header.
Make up the packet. The MTU is 1500 bytes in Ethernet, but the MTU size may be different in other physical networks. In such a case, it is of course possible to change the transmission period of the IP header according to the MTU size. It is. In the present invention, "I
The condition is that the total bytes of the TS packet payload from the TS packet including the P header to the transmission of the next TS packet including the IP header should not exceed the MTU byte number.

Next, a method of forming an MPEG-TS packet with the structure shown in FIGS. 1, 2 and 3 and processing it by an interwork unit to transmit it to an IP network will be described. FIG. 12 is an embodiment showing a flow of processing in the interworking unit. Here, it is assumed that the CATV video server transmits the MPEG-TS signal by the encapsulation method as shown in FIG. In the interwork unit, as shown in the processing procedure of FIG. 12, the transmitted MPEG-TS signal (packet) is input (procedure 100), and a signal to be transmitted to the IP network is extracted therefrom. The selection of the MPEG-TS packet is performed by checking the PID in the TS packet header. (Step 102) If the packet is not a packet to be transmitted to the IP network, the packet is discarded (Step 111). If the packet is to be transmitted to the IP network, a flag indicating whether or not there is an adaptation field in the TS packet header is checked (steps 104 and 105). As a result of this flag, if there is an adaptation field, the TS of the packet
The header is deleted (step 106), and subsequently, the flag information of the adaptation field is deleted (step 107). As a result, the data of the private data portion of the adaptation field and the data portion of the subsequent payload are output (step 108). As a result of checking the flag indicating the adaptation field of the TS header (steps 104 and 105), if there is no adaptation field, only the TS header of the TS packet is deleted and the payload data is output (step 11).
2). As a result of this processing, the TS header is deleted, and the IP packet header stored in the private data and the image data are subsequently transmitted from the interwork unit as a payload. As described above, according to the encapsulation of this embodiment, the inspection of two flags (PI
An IP packet can be generated from the MPEG-TS by only extremely simple processes such as inspection of D, inspection with / without adaptation and discarding of unnecessary data portions. An enormous effect that a processor can be used is obtained.

Next, with reference to FIG. 11, a description will be given of a process of converting an IP packetized video signal into an MPEG-TS signal again. An IP packet including data including an IP header, a UDP header, an RTP header, and a PES is input to the interwork unit 54 shown in FIGS. Therefore, private data in which a 2-byte adaptation-related flag and an IP-related header (IP, UDP, RTP header) are put together is stored in the TS as an adaptation field. The remaining payload of this TS is filled with PES data, and finally forms a 188-byte TS packet. The payload of the remaining IP packets is divided into 184 bytes and each is accommodated in the TS payload. Although the IP header cannot be used inside the CATV network, if the IP header is discarded and only the payload portion is stored in the TS payload, a TS having a shortage of data bytes occurs. In this case, processing such as padding of insufficient data is required, which is not preferable because it complicates the processing. Therefore, the transmitted CA
It is better to restore to the same packet configuration as inside the TV network. Note that there is actually no problem if only the number of bytes matches, so it is also possible to insert dummy data having the same number of bytes as the IP header. As described above, the private data in the adaptation field is
, The data may be invalid.

Third Embodiment FIG. 4 is a view showing a third embodiment of the present invention. The configuration of the network to which this embodiment is applied is the network configuration shown in FIGS. 8 and 9 similarly to the first embodiment. The difference between the embodiment of FIG. 4 and the embodiments of FIGS.
One is that the adaptation field is simultaneously transmitted with the program clock reference (PCR), and the other is that the IP packet transmitted as private data is transmitted with the RTP header included. In the RTP protocol, a field for recording time information (time stamp) is provided inside a packet header in order to guarantee data transmission such as video that requires real-time performance. M
The CATV terminal receiving the PEG-TS also uses PCR to reproduce the system clock of the decoding circuit, and the RTP time stamp is a digitized time based on a basic frequency of 90 kHz, similar to PCR. Therefore, it can be used as an RTP time stamp. In the embodiment of FIG. 4, the PCR transmitted in the PCR field of the adaptation field
Is used for the RTP time stamp field. The RTP time stamp is 32 bits,
Since the basic part of the PCR expresses the time information with a bit width of 33 bits, the lower 32 bits of the PCR
If the time stamp is P, the bit width can be matched. The advantage of using the time information delivered by the PCR as the time stamp of the RTP is as follows.
Even when the PCR is replaced for the purpose of correcting the packet delivery jitter generated inside the CATV network, the corrected time information can be finally incorporated into the RTP header.

Fourth Embodiment FIG. 10 is an embodiment showing the encapsulation of data when performing image distribution from the server 52 of FIG. 8 connected to the IP network to the CATV network 56. In the case of transmitting and receiving this image, the MPEG image signal (P
ES) into an MPEG-TS signal. The processing of this conversion operation will be described with reference to FIG. IP
When transmitting an image in a packet, video data is encapsulated in a PES format to facilitate conversion to a TS. Therefore, this IP packet is composed of an IP header and a PES format payload. In this conversion operation,
The IP packet size (the size of the data including the IP header and the payload) is set to a value obtained by subtracting 2 from the packet size and becomes an integral multiple of 184, and transmitted from a server in the IP network. I do. IP
When converting a packet to MPEG-TS, the head portion including the IP packet header is extracted as 182 bytes, added with an adaptation field flag (2 bytes), and stored as a 184-byte payload of MPEG-TS. In addition, MPEG-TS
An MPEG-TS packet is configured by adding a header.
Subsequent IP packets are divided every 184 bytes, and a TS packet header is added to this to convert it into MPEG-TS. There is a condition that the size of an IP packet is an integral multiple of 184 bytes and the sum of 182 bytes. Therefore, even if the IP packet is stored in the payload of the MPEG-TS packet, the IP packet must be stored in the TS payload without leaving extra bytes. Becomes possible. As described above, the feature of the present embodiment is that, by setting a limit on the size of an IP packet transmitted from a server of an IP network transmitting an MPEG image, packet division / reconstruction in an interwork unit becomes extremely simple. It is in such a point.

When the RTP protocol is used as a modification of the present embodiment, and the RTP time stamp is inserted as a PCR, the entire IP packet is taken into account in consideration of the PCR field (6 bytes) provided in the adaptation field. The length may be set to a value obtained by adding 178 bytes to an integral multiple of 184 bytes.

Fifth Embodiment A fifth embodiment is a modification of the second embodiment. In the encapsulation of the IP packet of FIG. 1 used in the second embodiment, MPEG-
Although the IP header is directly mapped to the private data of the TS, in this embodiment, as shown in FIG. 15, an area 150 indicating the attribute of the private data is provided in the first byte of the private data. By providing a flag in the area of this attribute, it is explicitly indicated that the content transmitted as private data is an IP header. The interworking unit uses this flag to
By determining whether the packet is a P packet, it is possible to determine use / discard. Since the data in the attribute area is unnecessary in the IP network, it must be discarded at the time of protocol conversion inside the interwork unit.

In FIG. 15, an example in which a 1-byte attribute area is provided has been described. However, it is easy to understand that this area does not necessarily have to be 1 byte and may be a plurality of bytes.

[0032]

As described above, according to the present invention, the CATV network can be interconnected by using a network connected worldwide such as the Internet, and the effect of reducing the operating cost by jointly using the program contents can be obtained. Can be Internet and CAT
It is also possible to greatly reduce the processing required for protocol conversion required for connecting the V line, thereby achieving an enormous effect that an interworking unit can be configured even with a low-cost processing device. Can be

[Brief description of the drawings]

FIG. 1 shows an embodiment of a system for encapsulating an IP header in an MPEG-TS packet and transmitting it.

FIG. 2 is an embodiment of a method of encapsulating an IP header and a UDP header in an MPEG-TS packet and transmitting the packet.

FIG. 3 shows an embodiment of a method of encapsulating an IP header, a UDP header, and an RTP header in an MPEG-TS packet and transmitting the packet.

FIG. 4 shows an embodiment of a method of encapsulating by including PCR in adaptation.

FIG. 5 is an exemplary view for explaining an embodiment in which the PCR transmitted in FIG. 4 is stored in an RTP time stamp.

FIG. 6 shows an embodiment of a method for constructing an IP packet from a TS packet.

FIG. 7 is a view for explaining the structure of an IP packet header.

FIG. 8 is an embodiment of a system for connecting a CATV network using the Internet.

FIG. 9 is an embodiment of a network configuration for connecting two CATV networks to the Internet.

FIG. 10 I sent from a server on an IP network
An embodiment in which a signal transmitted by a P packet is converted into an MPEG-TS packet.

FIG. 11 shows an embodiment in which a packet converted to IP by an interworking apparatus is converted to MPEG-TS again.

FIG. 12 is a flowchart illustrating a flow of signal processing of the interwork unit.

FIG. 13 is a view for explaining the structure of MPEG-TS.

FIG. 14 is a view for explaining the structure of an MPEG-TS header.

FIG. 15 is a view for explaining an embodiment in which a flag indicating an IP packet is provided in private data.

[Explanation of symbols]

1 ... TS header, 2 ... Adaptation field, 3
... Payload (PES), 4 ... Adaptation field flag, 5 ... Private data, 6 ... IP header, 10 ... UDP header, 14 ... RTP header, 23 ...
PCR base, 25 PCR extension, 26 RTP time stamp, 52 Internet, 51 Internet router, 52 Internet image server, 54 Internetwork unit, 55 CATV image server, 56 C
ATV network, 57: STB, 58: Internet image client, 62: Interwork unit, 8
0: payload of IP packet, 131: adaptation field, 180: flag.

Claims (10)

[Claims] (1) At least Moving Picture Experts Group
-2 (MPEG2) system is a CATV system that transmits digital video signals compressed by the ITU-T (International
al Telecommunication Union) Recommendation H. Transmission protocol and Internet Engineering Task specified in 222.0
Force (IETF) Internet Protocol (RF79
1) having interwork means for converting a method of transmitting a video according to 1), and
A CATV system, wherein a TV network is interconnected via a network using an Internet protocol to transmit an MPEG video signal. 2. The method according to ITU-TH. 22. This is a data encapsulation method for an MPEG transport packet specified by Recommendation 222.0, which encapsulates information necessary for configuring header information of an Internet protocol packet as private data of an adaptation field of the transport stream packet. A data encapsulation method and a data encapsulation method, wherein the data encapsulation is periodically transmitted. 3. The method of ITU-T H.3. 22. A data encapsulation method for an MPEG transport stream packet specified by the Recommendation 222.0, in which an Internet protocol packet header is stored as private data of an adaptation field of the transport stream packet, and the Internet protocol packet header is A data encapsulation method and a transmission method, wherein a transport packet including the data is periodically transmitted. 4. A method for transmitting at least a video signal in a PES format compressed by the MPEG system using an Internet protocol, wherein the size of an IP packet formed by the Internet protocol is larger than the size of the IP packet. An MPEG video transmission system, wherein a value obtained by subtracting 2 is an integral multiple of 184. 5. A method for transmitting at least a PES format video signal compressed by the MPEG system using an Internet protocol, wherein the size of an IP packet formed by the Internet protocol is larger than the size of the IP packet. An MPEG video transmission system, wherein a value obtained by subtracting 8 is an integer multiple of 184. 6. An MPEG transport stream transmission method according to claim 2, wherein header information of an Internet protocol packet is encapsulated by a private data field of an adaptation field.
This is a method of transmitting a program clock reference (PCR) signal by including it in the adaptation field. The UDP protocol and the RTP protocol are used as the Internet protocol, and the basic PCR is added to the 32-bit time stamp signal of the RTP protocol header.
A conversion method between the MPEG protocol and the Internet protocol, wherein lower 32 bits of data bits are duplicated and used. 7. A network connected to a first network for transferring TS packets, a video source connected to the first network, and both the first network and a second network for transferring IP packets. When transmitting video data from the video source to the protocol converter via the first network, the video source includes a plurality of protocol converters formed from the same video data. An adaptation field is inserted into at least one of the TS packets, and an IP header is stored in the inserted adaptation field.
To the network of the above, the protocol conversion device,
A CATV system characterized by extracting an IP header from a TS packet into which an adaptation field has been inserted, converting the TS packet into an IP packet using the extracted IP header, and transmitting the IP packet to the second network. 8. The CATV system according to claim 7, wherein said video source inserts an adaptation field and stores an IP header at a rate of one out of every N consecutive TS packets. 9. The CATV system according to claim 8, wherein said protocol converter converts N consecutive TS packets into one IP packet. 10. A protocol conversion method for converting a TS packet into an IP packet, comprising the steps of: starting from a TS packet in which an adaptation field is inserted among a plurality of TS packets having the same PID value;
Extracts the header, the extracted IP header, and the TS from which the IP header is extracted
A protocol conversion method comprising forming one IP packet using data of a payload of a packet and data of a payload of at least one TS packet subsequent to a TS packet from which an IP header has been extracted.