1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T J.127TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2004) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Interactive systems for digital television distribution Transmission protocol for multimed
2、ia webcasting over TCP/IP networks ITU-T Recommendation J.127 ITU-T Rec. J.127 (06/2004) i ITU-T Recommendation J.127 Transmission protocol for multimedia webcasting over TCP/IP networks Summary This Recommendation defines a transmission protocol for multimedia webcasting over TCP/IP networks. The p
3、rotocol consists of a presentation description and session control. The presentation description is based on the XHTML format, and it specifies properties of the media such as URI, content type, content size, accounting information, and so on. First of all, a terminal receives the presentation descr
4、iption, and sets up in accordance with the description. Then the terminal starts transmission of the media in accordance with the session control, which is based on HTTP. The session control supports starting the session, retrieving the media data and ending the session. In addition, a remote camera
5、 control scheme is also defined in the session control. Since the protocol defined in this Recommendation is similar to the WWW browsing system, problems related to the UDP/IP streaming such as the Firewall issue are resolved by this Recommendation, and the implementation will have less affect. Sour
6、ce ITU-T Recommendation J.127 was approved on 29 June 2004 by ITU-T Study Group 9 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. J.127 (06/2004) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicatio
7、ns. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication
8、Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of inform
9、ation technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agenc
10、y. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some ot
11、her obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or impl
12、ementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development proces
13、s. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly
14、urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. J.127 (06/2004) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informati
15、ve references 1 3 Terms and definitions . 1 4 Abbreviations 2 5 Presentation Description. 2 5.1 XHTML Presentation Description Format. 2 5.2 Element . 3 5.3 Element . 4 6 Session control 6 6.1 Retrieval of the content size . 6 6.2 Data transmission . 7 6.3 Normal termination 8 6.4 Abnormal terminati
16、on 8 6.5 Camera control . 9 ITU-T Rec. J.127 (06/2004) 1 ITU-T Recommendation J.127 Transmission protocol for multimedia webcasting over TCP/IP networks 1 Scope This Recommendation defines a transmission protocol for multimedia webcasting of various media format over TCP/IP networks. Such formats in
17、clude J.123 and J.124 as well as other media formats. However, the protocol defined in this Recommendation is independent from the media format, which is outside the scope of this Recommendation. The protocol consists of a presentation description and session control. The presentation description is
18、 based on the XHTML format, and the session control is based on HTTP. Issues not especially specified here shall comply with XHTML and HTTP. 2 References 2.1 Normative references The following ITU-T Recommendations and other references contain provisions which, through reference in this text, consti
19、tute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Rec
20、ommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. 1 W3C Recommendation, XHTML 1.0: The Extensi
21、ble HyperText Markup Language. 2 IETF RFC 2068 (1997), Hypertext Transfer Protocol HTTP/1.1. 2.2 Informative references 3 ITU-T Recommendation J.123 (2002), Multiplexing format for webcasting on TCP/IP network. 4 ITU-T Recommendation J.124 (2004), Multiplexing format for multimedia webcasting over T
22、CP/IP networks. 3 Terms and definitions This Recommendation defines the following terms: 3.1 file downloading: Program transmission method whereby the program starts playing after the entire data has been downloaded. 3.2 live transmission: Program transmission method whereby the program starts playi
23、ng after a certain amount of data has been buffered while receiving subsequent data in the background, where the program is fed in real time by the content provider. 3.3 VoD transmission: Program transmission method whereby the program starts playing after a certain amount of data has been buffered
24、while receiving subsequent data in the background, where the program is completely created by the content provider. 2 ITU-T Rec. J.127 (06/2004) 4 Abbreviations This Recommendation uses the following abbreviations: HTTP Hypertext Transfer Protocol MIME Multipurpose Internet Mail Extensions VoD Video
25、-on-Demand XHTML Extensible HyperText Markup Language 5 Presentation Description 5.1 XHTML Presentation Description Format The overall program and the properties of the media shall be defined by a presentation description in XHTML 1. The presentation description may be obtained by the receiver using
26、 HTTP or other means such as e-mail and may not necessarily be stored on the server. The presentation description contains a description of the media streams making up the program, including their location, title, encoding types, data size, and other parameters that enable the receiver to start retr
27、ieving the most appropriate media. The presentation description is written by the element with the elements of XHTML. An example is shown below. Elements defined by this Recommendation are written with bold letters. Webcasting Test Page Elements used in the presentation description are summarized in
28、 Table 1. In Table 1, M/O stands for “Mandatory“ or “Optional“, respectively. ITU-T Rec. J.127 (06/2004) 3 Table 1/J.127 Elements defined in this Recommendation Element Attibute M/O Value Description object data M URI String Actual location of the media file. object type M MIME Type MIME type of the
29、 media. object copyright O “yes“ | “no“ Copyright control. object standby M String The displayed text of the link. param name=“ac“ value=“.“ valuetype=“data“ O String Access Ticket. param name=“bitrate“ value=“.“ valuetype=“data“ O Numeric String Bit rate of the content in bit/s. param name=“camctl“
30、 value=“.“ valuetype=“data“ O Numeric String Camera control capability. param name=“disposition“ value=“.“ valuetype=“data“ M String Types of the content distribution, which stands for downloading, VoD transmission, or live transmission. param name=“duration“ value=“.“ valuetype=“data“ O Numeric Str
31、ing Duration of the content in milliseconds. param name=“size“ value=“.“ valuetype=“data“ O Numeric String File size of the content in bytes. This field is effective for downloading and VoD streaming. param name=“title“ value=“.“ valuetype=“data“ M String Title text of the content. 5.2 Element The f
32、ollowing attributes for the element are defined in this Recommendation. 5.2.1 data This is a mandatory attribute that specifies the URI of the media to be transmitted. In this Recommendation, since the media is transmitted by HTTP, the scheme of the URI shall be http, or the URI shall start with “ht
33、tp:/“. 5.2.2 type This is a mandatory attribute that specifies the MIME type of the media to be transmitted. For example, “video/MP2T“ is specified for MPEG-2 Transport Stream. 5.2.3 copyright This attribute takes “yes“ or “no“, and this is optional. The default value is “no“. The copyright attribut
34、e takes effect as follows. yes: The content is protected from storing. The media data cannot be stored in the device after playing. no: The media data can be stored in the device after playing. If this attribute is not specified, the terminal shall handle the file as storing allowed. 4 ITU-T Rec. J.
35、127 (06/2004) 5.2.4 standby This is a mandatory attribute that specifies the displayed text of the link to the media. It will typically be “Click Here“ or the name of the content. 5.3 Element Parameters of the media are specified with the element in the HTML description. The following parameters are
36、 defined in this Recommendation. Each parameter is identified by the name attribute and the value is specified by the value attribute. For the all parameters, valuetype=“data“ shall be included in each element. The terminal shall ignore unknown parameters. 5.3.1 ac This is an optional parameter and
37、the value attribute specifies the access ticket. The maximum length of the value is 512 bytes. The terminal that obtained the access ticket from the ac parameter in the presentation description shall use this ticket when the terminal carries out the session control as “ac=“ parameter in the HTTP req
38、uest. See also clause 6. This is used for identification of fee collection. 5.3.2 bitrate This is an optional parameter. It specifies the total bit rate of the media in bits per second. If the media has video and audio track, the bitrate value will be the sum of the bit rate of each track. If the me
39、dia has multiple bit rates for adaptive bit rate changing, all the values are specified with : separator. For example, 5.3.3 camctl This is an optional parameter that shows the camera control capability of the content. The value consists of 8-numeric letters and each digit shows the capability of ea
40、ch camera control. The following table explains the camera control value (=“XYZABCDE“), where the left-most digit is firstly described. Table 2/J.127 Camera control parameters No. Value Description 1 0 or 1 If the value is 1, panning control is supported. 2 0 or 1 If the value is 1, tilting control
41、is supported. 3 0 or 1 If the value is 1, zooming control is supported. 4 0 Reserved 5 0 Reserved 6 0 Reserved 7 0 Reserved 8 0 Reserved ITU-T Rec. J.127 (06/2004) 5 For example, the following shows the case where the content supports the pan and the zoom control. The “camctl“ parameter is effective
42、 only for the camera control enabled content, which is specified by the “disposition“ parameter described below. The terminal shall recognize the content has camera control capability only when the “camctl“ parameter exists and the value has an appropriate setting. The terminal shall recognize the c
43、ontent has no camera control capability if the value is not specified or the value is “00000000“. The terminal shall recognize the content has no camera control capability if the value has more than eight digits or less than eight digits. The terminal shall recognize the content has no camera contro
44、l capability if the value contains any digits other than 0 or 1. The terminal shall ignore the “camctl“ parameter if any reserved field contains a non-zero. Actual actions for the camera control are described in 6.5. 5.3.4 disposition The disposition parameter defines the content type, its applicati
45、on, distribution scheme, and so on. The existence of the disposition parameter is mandatory. In this Recommendation, the disposition parameter itself is not defined, but what the parameter specifies is defined as follows. Category of the content: Video (including Video and Audio), Audio, Voice, MIDI
46、, Still Image, Animation, Application Program (e.g., JAVA), etc. Transmission scheme of the content: File downloading, VoD transmission, Live transmission. Purpose of the content: Just viewing, Storing, Particular use (Wallpaper, Screensaver, Alarm, etc.). 5.3.5 duration This is an optional paramete
47、r. It specifies the duration of the media in milliseconds. If the media has different duration of video and audio track, the value is the longest duration in the tracks. 5.3.6 size This is an optional parameter. It specifies the data size of the media in bytes, which helps the terminal to obtain the
48、 content size in advance of transmitting. Regarding the file downloading and the VoD transmission, the file is already created before transmitting. Therefore, the value of the size parameter is the same as the size of the file. In addition, if the media has multiple bit rates for adaptive bit rate c
49、hanging, each size corresponding to each bit rate is specified with : separator. For example, If this parameter is not specified in the presentation description, the terminal shall require the content size from the server at the beginning of the transmission. This is carried out with the HEAD request of HTTP. Details are described in 6.1. For the live transmission, the file size cannot be estimated before transmission. In this case, the size value indicates the maximum size of the stream that is continuously transmitted. For example, if the size
