1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T J.288 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2016) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Digital transmission of television signals Part 2 Encapsu
2、lation of type length value (TLV) packet for cable transmission systems Recommendation ITU-T J.288 Rec. ITU-T J.288 (03/2016) i Recommendation ITU-T J.288 Encapsulation of type length value (TLV) packet for cable transmission systems Summary Recommendation ITU-T J.288 proposes an encapsulation schem
3、e for type length value (TLV), a data structure specified in Recommendation ITU-R BT.1869, for cable transmission systems designed on the basis of Recommendation ITU-T J.83. Many of the existing digital broadcasting systems use the Motion Picture Experts Group version 2 (MPEG-2) transport stream (TS
4、) as their input format. In contrast, variable-length packets formats such as TLV are specified for transmitting Internet protocol (IP) packets efficiently over broadcasting channels as aggregates of variable-length packets. In order to transmit TLV with the existing Recommendation ITU-T J.83 transm
5、ission system, it is necessary that variable-length TLV packets be fragmented and encapsulated into fixed-length 188-byte packets. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T J.288 2016-03-15 9 11.1002/1000/12770 * To access the Recommendation, type the URL http:/handle.
6、itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T J.288 (03/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telec
7、ommunications, information and communication technologies (ICTs). 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 telecom
8、munications on a worldwide basis. The World Telecommunication 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 pro
9、cedure laid down in WTSA Resolution 1. In some areas of information 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 tel
10、ecommunication administration and a recognized operating agency. 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
11、these mandatory provisions are met. The words “shall“ or some other 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 RIGHTSI
12、TU draws attention to the possibility that the practice or implementation 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 mem
13、bers or others outside of the Recommendation development process. 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, implementers are cautioned that this may n
14、ot represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T J.288
15、 (03/2016) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 System overview . 2 7 Encapsulation scheme . 3 7.1 Fragmentation of TLV packets . 3 7.2 Forma
16、t of fragmented TLV packet . 3 7.3 Header of fragmented TLV packet . 3 7.4 top_pointor_field of fragmented TLV packet 4 7.5 Payload of fragmented TLV packet . 4 8 Restoration to original TLV packets . 4 Appendix I Examples of use cases for encapsulation scheme of TLV . 5 Bibliography. 7 Rec. ITU-T J
17、.288 (03/2016) 1 Recommendation ITU-T J.288 Encapsulation of type length value (TLV) packet for cable transmission systems 1 Scope This Recommendation defines an encapsulation scheme for type length value (TLV), a data structure specified in ITU-R BT.1869, for its transmission over existing cable TV
18、 systems designed on the basis of ITU-T J.83. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendatio
19、ns 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 Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly publish
20、ed. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.222.0 Recommendation ITU-T H.222.0 (2014) | ISO/IEC 13818-1:2000, Information technology Generic coding of moving pictures and associated audio information:
21、 Systems. ITU-T J.83 Recommendation ITU-T J.83 (2007), Digital multi-programme systems for television, sound, and data services for cable distribution. ITU-R BT.1869 Recommendation ITU-R BT.1869 (2010), Multiplexing scheme for variable-length packets in digital multimedia broadcasting systems. 3 Def
22、initions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 fragmented TLV packet: A fixed-length packet that has fragmented type length value (TLV). 4 Abbreviations and acronyms This Recommendation uses the following abbr
23、eviations and acronyms: IP Internet Protocol MPEG-2 Motion Picture Experts Group version 2 TLV Type Length Value TS Transport Stream 2 Rec. ITU-T J.288 (03/2016) 5 Conventions In this Recommendation: The keywords “is required to“ indicate a requirement which must be strictly followed and from which
24、no deviation is permitted if conformance to this document is to be claimed. The keywords “is recommended“ indicate a requirement which is recommended but which is not absolutely required. Thus this requirement need not be present to claim conformance. The keywords “is prohibited from“ indicate a req
25、uirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed. The keywords “can optionally“ indicate an optional requirement which is permissible, without implying any sense of being recommended. This term is not intended to imply
26、 that the vendors implementation must provide the option and the feature can be optionally enabled by the network operator/service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with the specification. In the body of this document and its annexes
27、, the words shall, shall not, should, and may sometimes appear, in which case they are to be interpreted, respectively, as is required to, is prohibited from, is recommended, and can optionally. The appearance of such phrases or keywords in an appendix or in material explicitly marked as informative
28、 are to be interpreted as having no normative intent. 6 System overview The system overview is shown in Figure 1. At the headend, input TLV packets are fragmented and encapsulated into a fixed-length packet called a fragmented TLV packet. The fragmented TLV packets are transmitted with an existing t
29、ransmission scheme specified in ITU-T J.83. Each fragmented TLV packet must be 188 bytes in length and its first byte must have the value of 47HEX. These specifications were set because the input format of the transmission scheme specified in ITU-T J.83 is a Motion Picture Experts Group version 2 (M
30、PEG-2) transport stream (TS) consisting of a continuous data stream of fixed-length 188-byte packets. The first byte of an MPEG-2 TS is specified to be a sync byte having the value of 47HEX. MPEG-2 is video coding specified in b-ITU-T H.262, while audio coding is specified in b-ISO/IEC 13818-3 and i
31、n b-ISO/IEC 13818-7. TS is a data structure specified in ITU-T H.222.0. On the receiver side, fragmented TLV packets are combined and restored to the original TLV packets. Figure 1 System overview Using this encapsulation scheme enables various use cases, examples of which are shown in Appendix I. R
32、ec. ITU-T J.288 (03/2016) 3 7 Encapsulation scheme 7.1 Fragmentation of TLV packets Figure 2 shows how the TLV packets are fragmented into fixed 188-byte packets. Each TLV packet has the information of its length and type. The length of a TLV packet is indicated by the length field. The type of pack
33、et shows IPv4, IPv6, header compressed Internet protocol (IP) packets, and transmission control signals. In order to transmit variable-length TLV packets like an MPEG-2 TS with the transmission scheme specified in ITU-T J.83, TLV packets are fragmented and encapsulated into a fragmented TLV packet,
34、which must be a fixed-length 188-byte packet. There may be multiple TLV packets in one fragmented TLV packet in order to encapsulate them efficiently. Figure 2 Fragmentation of TLV packets 7.2 Format of fragmented TLV packet A fragmented TLV packet consists of a 3-byte packet header, top_pointer_fie
35、ld and payload (shown in Figure 3). Figure 3 Format of fragmented TLV packet 7.3 Header of fragmented TLV packet The header of the fragmented TLV packet is shown in Table 1. The header of the fragmented TLV packet consists of the first three of the 188 bytes comprising the packet. The header identif
36、ies the payload as belonging to the fragmented TLV packet. Other values of the header may indicate other service payloads. NOTE The semantic definition of the fields in a fragmented TLV packet is as follows: sync_byte: This is a fixed 8-bit field whose value is 0100 0111 (0x 47). transport_error_ind
37、icator: The transport error indicator is a flag that indicates whether there are any bit errors in the reception of the fragmented TLV packet. If this flag contains 1, it indicates that the fragmented TLV packet has an uncorrectable error of at least one bit. TLV_start_indicator: This indicator show
38、s when there is at least one start of a TLV packet (1) or when there is no start (0). PID: This is a fixed 13-bit field whose value must be set to a unique value. This unique value differentiates the fragmented TLV packet from other TS packets. 4 Rec. ITU-T J.288 (03/2016) Table 1 Header of fragment
39、ed TLV packet Parameter No. of bits Description sync_byte 8 0x47: same value as MPEG-2 TS sync byte transport_error_indicator 1 Indicates that at least one error has occurred in the packet. TLV _start_indicator 1 A value of one indicates the presence of at least one start of a TLV packet. 0 1 PID 13
40、 A unique value for a fragmented TLV packet 7.4 top_pointor_field of fragmented TLV packet The top_pointor_field is a fixed 8-bit field whose value indicates the start position of the TLV packet in the payload. The fourth byte of the fragmented TLV packet (first byte following the header) will be a
41、top_pointor_field if the TLV_start_indicator of the header is set to 1. If the TLV_start_indicator is set to 0, the top_pointor_field does not exist. 7.5 Payload of fragmented TLV packet The payload of a fragmented TLV packet carries a portion of the TLV. If top_pointor_field exists in the fragmente
42、d TLV packet, the payload is 184 bytes following the top_pointor_field. If top_pointor_field does not exist in the fragmented TLV packet, the payload is 185 bytes following the header. 8 Restoration to original TLV packets On the receiver side, fragmented TLV packets that contain desired TLV packets
43、 are considered demodulation output. After that, the TLV_start_indicator, the top_pointor in the fragmented TLV packet and information on the packet length in the TLV packet are used to restore an original TLV packet from the fragmented TLV packets. Rec. ITU-T J.288 (03/2016) 5 Appendix I Examples o
44、f use cases for encapsulation scheme of TLV (This appendix does not form an integral part of this Recommendation.) Three examples of use cases for the encapsulation scheme of TLV are shown in clauses I.1 to I.3. I.1 Use case 1 One TLV stream is input and transmitted. See Figure I.1. Figure I.1 Use c
45、ase 1 I.2 Use case 2 One TLV stream and one MPEG-2 TS stream are input and transmitted. See Figure I.2. Figure I.2 Use case 2 NOTE In this case, a specified PID value for the fragmented TLV packet header is used to identify stream types. Other values of the PID may indicate other payloads of the MEP
46、G-2 TS packet. Figure I.3 shows the interleaving of a fragmented TLV packet with other digital information (digital video in the example shown). Figure I.3 Example of interleaving of a fragmented TLV packet with MPEG-2 TS packets H e a de r= fra gm e nt e d T L V pa c ke t H e a de r = fra gm e nt e
47、 d T L V pa c ke t H e a de r= vi de oH e a de r= fra gm e nt e d T L V pa c ke t H e a de r= vi de oH e a de r= fra gm e nt e d T L V pa c ke t H e a de r= vi de o fra gm e nt e d T L V pa c ke t pa yl oa d fra gm e nt e d T L V pa c ke t pa yl oa d fra gm e nt e d T L V pa c ke t pa yl oa d fra gm
48、 e nt e d T L V pa c ke t pa yl oa dD i gi t a l vi de o pa yl oa dD i gi t a l vi de o pa yl oa dD i gi t a l vi de o pa yl oa d6 Rec. ITU-T J.288 (03/2016) I.3 Use case 3 Multiple TLV streams or multiple MPEG-2 TS streams are input. In order to multiplex multiple streams, multiplexing frame of b-I
49、TU-T J.183 can be applied. See Figure I.4. Figure I.4 Use case 3 Rec. ITU-T J.288 (03/2016) 7 Bibliography b-ITU-T H.262 Recommendation ITU-T H.262 (2012) | ISO/IEC 13818-2:2013, Information technology Generic coding of moving pictures and associated audio information: Video. b-ITU-T J.183 Recommendation ITU-T J.183 (2016), Time-division multiplexing of multiple MPEG-2 transport streams and generic formats of transport streams over cable television systems. b-ISO/IEC 1381
