Electrical computers and digital processing systems: multicomput – Remote data accessing – Using interconnected networks
Reexamination Certificate
1998-09-04
2003-04-29
Coulter, Kenneth R. (Department: 2142)
Electrical computers and digital processing systems: multicomput
Remote data accessing
Using interconnected networks
C709S230000, C709S236000, C709S246000, C709S249000, C725S109000, C725S110000, C725S118000
Reexamination Certificate
active
06557031
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and system for transmitting an MPEG (Moving Picture Experts Group) image by use of the Internet Protocol (hereinafter referred to as IP). More particularly, the present invention relates to a network connection method using a transmission system conversion equipment for performing a rapid processing for conversion between an MPEG transport protocol and the Internet Protocol and a method for encapsulation of MPEG data to be transmitted. Also, the present invention relates to a method/equipment in which the conversion between an IP address and the PID (Packet Identifier) value of a TS (Transport Stream) packet is performed when a video signal transmitted using the Internet Protocol (IP) is to be transmitted by use of the H.222.0 system and a video transmission system which uses such a method/equipment.
As an international standard for a system for transmitting a video signal in a digitally coded form, “GENERIC CODING OF MOVING PICTURES AND ASSOCIATED AUDIO: SYSTEMS” has been prescribed as ISO(International Organization for Standard)/IEC(International Electrotechnical Commission) 13818-1, ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) H.222.0 Recommendation. This international standard for MPEG system (hereinafter referred to as H.222.0) has prescribed a standard for transmitting a video signal compressed on the basis of an MPEG system. Therein, two kinds of formats have been prescribed. One is a program stream (hereinafter abbreviated to PS) format supposing the transmission from a storage medium or the like for which the generation of bit error is relatively less. The other is a transport stream (hereinafter abbreviated to TS) format supposing a communication network for which the generation of transmission bit error is forecast.
Since in a code conversion system when a compressed or coded video signal is to be transmitted in a TS format, a brief description will be provided of conventional apparatus of a video transmission system based on the TS format. In an MPEG system the object of which is the coding and transmission of video and audio signals, an inputted video signal such as a television signal is digitized and the obtained digital signal is subjected to data compression by use of techniques including discrete cosine conversion, variable-length coding, and so forth. Though techniques used in conjunction with an audio signal are different from those in the case of the video signal, the audio signal is compressed by removing redundant data after digitization. The compressed signal is termed an elementary stream (hereinafter abbreviated to ES) and is data which forms an elementary part of the video/audio signal in conformity with the term. In the MPEG, this video/audio data is represented using the term of (bit) stream.
In a cable television or community antenna television (CATV), satellite communication network, asynchronous transfer mode transmission network (hereinafter abbreviated to ATM network) or the like in which an MPEG video signal is transmitted, it is supposed that the generation of bit error at the time of data transmission is relatively frequent. Therefore, an elementary stream (ES) is transmitted in a form partitioned into small packets in order to narrow a range over which a trouble caused by transmission error extends. The packetized elementary stream (hereinafter abbreviated to PES) has a format in which header information called PES header is added to ES. In the transmission in the communication network exemplified above, PES is transmitted with a form further partitioned into smaller 188-byte packets called transport stream (TS) packets. As shown in
FIG. 13
, the TS packet includes a 4-byte header and a 184-byte payload for storing data.
FIG. 14
shows the structure of the header of the TS packet. The TS header is composed of a 1-byte synchronization byte (Ox47)
133
, a flag
134
representative of the attribute of the TS packet (the explanation of the contents of the flag will be omitted since they are not important to the present invention), 13-bit packet identifiers (hereinafter abbreviated to PID)
135
and
136
, a scramble control identifier
137
, an adaptation field identifier
138
, and a 4-bit cyclic counter
139
used for checking the continuity of the packet. In the transport stream, a field called adaptation field can be transmitted prior to a data field which is called payload and is used for storing video data. A program clock reference (hereinafter abbreviated to PCR) aiming at the clock synchronization of the system and private data can be stored in the adaptation field. It is prescribed that when the adaptation field is transmitted using the TS packet, the existence of the adaptation field should be designated by an adaptation field identifier in the TS header.
Though the MPEG system is a system developed corresponding to CATV or digital satellite broadcasting, a service utilizing an MPEG image is recently provided by a network called the Internet having grown with the main object of data communication between computers. In order to ensure the interconnectability of communication in the Internet, the Internet Engineering Task Force (hereinafter abbreviated to IETF) is pushing on standardization. For the standard of an MPEG video transmission format, Request for Comment No. 2038: “RTP Payload Format for MPEG1/MPEG2 Video” (hereinafter abbreviated to RFC 2038) has standardized a transmission method and a packet encapsulation system. It is prescribed by RFC 2038 that the transmission should be made with ES, TS or PS of MPEG utilized as the format of a packet to be transmitted and that in order to prevent the degradation of resolution from being caused by transmission delay, the transmission should be made in accordance with “RTP: A Transport Protocol for Real-Time Applications” (hereinafter abbreviated to RTP) specified by RFC 1889. It is prescribed that an RTP packet should be stored in a packet based on a user datagram protocol (hereinafter abbreviated to UDP) and this UDP packet should be transmitted by use of the Internet Protocol packet (hereinafter abbreviated to IP packet). With the prior art described above, it is possible to transmit MPEG video data in such a manner that MPEG-TS packets are used in the CATV network while IP packets are used in the Internet.
A system for performing video transmission on the basis of an MPEG-TS system includes a digital satellite broadcasting system and a digital CATV system, as mentioned above. The digital CATV system of those services is a service closely related with an area. Generally, the digital CATV system is constructed with a relatively narrow area taken as a service providing area. Therefore, each CATV business proprietor possesses a CATV center (hereinafter referred to as head end) for delivering programs or contents and an access network for transmitting a video signal so that a ground/satellite broadcasting program received at the head end is retransmitted and/or programs or video contents stored in the head end are transmitted, as required. In such a conventional CATV service, it is required that programs other than broadcast programs should be stored in, for example, VTR or the like and reproduced in accordance with delivering schedule. In a video-on-demand (VOD) service or the like expected as a near-future CATV service, too, it is general that the service is structured in a form in which a digital compression signal of a program is held at a head end in a manner similar to that mentioned above. The video-on-demand service has a problem that a service maintenance cost including the purchase of a rebroadcasting right (or copyright) of video contents in order to hold the video contents, a digital compression processing for the video contents, the storage of compressed or coded video, and so forth is expensive and hence it is not commercially profitable unless the number of times of access to the same contents is made as large as possible. An effective method for solving thi
Mimura Itaru
Shibata Koichi
Suzuki Toshiaki
Antonelli Terry Stout & Kraus LLP
Coulter Kenneth R.
Hitachi , Ltd.
Kang Paul
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