1、 International Telecommunication Union ITU-T J.286TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2009) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Digital transmission of television signals Seamless splicing for heterogeneous ITU-T H.262
2、 ISO/IEC 13818-2 (MPEG-2 video) and ITU-T H.264 ISO/IEC 14496-10 bitstreams Recommendation ITU-T J.286 Rec. ITU-T J.286 (03/2009) i Recommendation ITU-T J.286 Seamless splicing for heterogeneous ITU-T H.262 | ISO/IEC 13818-2 (MPEG-2 video) and ITU-T H.264 | ISO/IEC 14496-10 bitstreams Summary For di
3、stribution of video content encoded in the multiple types of compression methods, bitstream domain splicing between these heterogeneous bitstreams are necessary to avoid picture quality degradation and latency caused by transcoding. Recommendation ITU-T J.286 defines a messaging format and constrain
4、ts on bitstreams to achieve seamless splicing of heterogeneous bitstreams that conform to Recommendation ITU-T H.262 | ISO/IEC 13818-2 (also known as “MPEG-2 video“) or Recommendation ITU-T H.264 | ISO/IEC14496-10 (also known as “MPEG-4 AVC“). The messaging format is defined as an extension of Recom
5、mendation ITU-T J.181, which is intended to enable the splicing device with relevant information of the bitstreams to be spliced. If the splicing device is aware of the video coding types of the subsequent bitstream in advance of the splicing event, it would be able to take more appropriate action f
6、or splicing of the different types of bitstreams. This Recommendation thus provides a mechanism to notify the type of the bitstream to be switched over. In addition, constraints on the bitstreams are also defined based on Recommendation ITU-T J.189 to facilitate seamless playback between MPEG-2 vide
7、o and ITU-T H.264 by the decoder that satisfies requirements for seamless splicing of heterogeneous bitstreams. For seamless splicing, such constraints can apply at the encoder when it compresses an input video or at the splicing device by making modifications on input bitstreams. The decoder is req
8、uired to be capable of seamless decoding and playback of concatenated bitstreams conforming to the constraints defined by this Recommendation. This means that a conventional dual-mode decoder requiring firmware reloading and resetting to change the mode might not be functional. How to apply the cons
9、traints at the encoder or at the splicing device, how to upgrade the existing ITU-T J.181 splicing devices to ITU-T J.286 ones, and how to develop the decoder for this system is design dependent, and outside the scope of this Recommendation. Source Recommendation ITU-T J.286 was approved on 22 March
10、 2009 by ITU-T Study Group 9 (2009-2012) under Recommendation ITU-T A.8 procedures. ii Rec. ITU-T J.286 (03/2009) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). T
11、he 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 Stand
12、ardization 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 information
13、 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 agency. Co
14、mpliance 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 other
15、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 implemen
16、tation 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 process. A
17、s 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 not represent the latest information and are therefore strongly urge
18、d to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 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.286 (03/2009) iii CONTENTS Page 1 Scope 1 2 References. 2 2.1 Normativ
19、e References 2 2.2 Informative References 2 3 Definitions 2 3.1 Terms defined elsewhere: . 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Bitstream splicing techniques . 3 5.1 Configuration 3 5.2 MPEG-2 Transport Stream syntax required for seamless splicing 4 5.3 Tra
20、nsport mechanism of scheduling information for splicing devices 4 Rec. ITU-T J.286 (03/2009) 1 Recommendation ITU-T J.286 Seamless splicing for heterogeneous ITU-T H.262 | ISO/IEC 13818-2 (MPEG-2 video) and ITU-T H.264 | ISO/IEC 14496-10 bitstreams 1 Scope While MPEG-2 video, defined in MPEG-2, is a
21、dopted in a number of television systems, it is expected that the video coding method will be shifted to ITU-T H.264 in order to take advantage of its improved coding efficiency. During the changeover period, there might be the situation where both MPEG-2 video and ITU-T H.264 exist as a compression
22、 method of video content. In addition to the migration purposes, there could be such cases that MPEG-2 video is preferably used even in the ITU-T H.264-based system to avoid transcoding when content owner wishes to maintain the original bitstreams. They can also take advantage of compression noise c
23、haracteristics of MPEG-2 video, which is preferable to some source materials using ITU-T H.264. These situations would require distribution of video content encoded in the multiple types of compression methods and bitstream domain splicing between these heterogeneous bitstreams. This Recommendation
24、defines a messaging format and constraints on bitstreams to achieve seamless splicing of heterogeneous bitstreams that conform to ITU-T H.262 | ISO/IEC 13818-2 (also known as “MPEG-2 video“) or ITU-T H.264 | ISO/IEC 14496-10 (also known as “MPEG-4 AVC“). The messaging format is defined as an extensi
25、on of ITU-T J.181, which is intended to enable the splicing device with relevant information of the bitstreams to be spliced. If the splicing device is aware of the video coding types of the subsequent bitstream in advance of the splicing event, it would be able to take more appropriate action for s
26、plicing of the different types of bitstreams. This Recommendation thus provides a mechanism to notify the type of the bitstream to be switched over. In addition, additional constraints on the bitstreams are also defined based on ITU-T J.189 to facilitate seamless playback between MPEG-2 video and IT
27、U-T H.264 by the decoder that satisfies requirements for seamless splicing of heterogeneous bitstreams. “Seamless splicing“, as used in this Recommendation, means switching from one video elementary stream to a second video elementary stream in the following manner: Continuity of the spliced bitstre
28、am is maintained; Switching occurs at a Transport Stream packet boundary; No underflow or overflow of the decoder buffer occurs as a result of the splice; Correct syntax as defined in ITU-T H.222.0 is maintained and the splice may result in discontinuities in timebase or continuity counter; No visib
29、le artifacts in the reconstructed baseband video are introduced; No audio codec change is supported by this Recommendation. For seamless splicing, such constraints can apply at the encoder when it compresses an input video or at the splicing device by making modifications on input bitstreams. The de
30、coder is required to be capable of seamless decoding and playback of concatenated bitstreams conforming to the constraints defined by this Recommendation. This means that a conventional dual-mode decoder that requires firmware reloading and resetting to change the mode might not be able to be used.
31、How to apply the constraints at the encoder or at the splicing device, how to upgrade the existing ITU-T J.181 splicing devices to ITU-T J.286 ones, and how to develop the decoder for this system is design dependent, and outside the scope of this Recommendation. 2 Rec. ITU-T J.286 (03/2009) 2 Refere
32、nces 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 Recommendations and other references are subject to revision; users
33、 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 published. The reference to a document within this Recommenda
34、tion 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 (2006) | ISO/IEC 13818-1:2007, Information technology Generic coding of moving pictures and associated audio information: Systems. ITU-T H.264 Recommendation ITU-T H.264 (2005
35、) | ISO/IEC 14496-10:2005, Advanced video coding for generic audiovisual services. ITU-T J.181 Recommendation ITU-T J.181 (2004), Digital program insertion cueing message for cable television systems. ITU-T J.189+Cor1 Recommendation ITU-T J.189 (2002), Seamless splicing for MPEG-2 bitstreams, plus C
36、orrigendum 1 (2003). MPEG-2 Recommendation ITU-T H.262 (2000) | ISO/IEC 13818-2:2000, Information technology Generic coding of moving pictures and associated audio information: Video. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following term defined elsewhere: 3.1.1 NAL u
37、nit ITU-T H.264: A syntax structure containing an indication of the type of data to follow and bytes containing that data in the form of RBSP interspersed as necessary with emulation prevention bytes. Other definitions refer to ITU-T J.181 and ITU-T J.189+Cor1. 3.2 Terms defined in this Recommendati
38、on This Recommendation defines the following term: 3.2.1 MPEG-2 video: The video coding format defined in ITU-T H.222.0. The transport syntax of a spliceable bit stream is recommended in ITU-T H.222.0, so called MPEG-2 Transport Stream or MPEG-2 TS. 4 Abbreviations and acronyms This Recommendation u
39、ses the following abbreviations and acronyms: CPB Coded Picture Buffer IDR Instantaneous Decoding Refresh MPEG Moving Picture Experts Group NAL Network Adaptation Layer PES Packetized Elementary Stream PID Packet Identifier Rec. ITU-T J.286 (03/2009) 3 PPS Picture Parameter Set RBSP Raw Byte Sequenc
40、e Payload SEI Supplemental Enhancement Information SPS Sequence Parameter Set TS Transport Stream VBV Video Buffer Verifier 5 Bitstream splicing techniques 5.1 Configuration The following descriptions are based on clause 4.1 of ITU-T J.189+Cor1 with some enhancements. The transport syntax of a splic
41、eable bit stream is recommended in ITU-T H.222.0, so called MPEG-2 Transport Stream or MPEG-2 TS. MPEG-2 TS carries both MPEG-2 encoded and ITU-T H.264 encoded video bit streams. A spliceable bit stream means a PID stream whose discontinuity in a time-stamp or a time base can be processed seamlessly
42、 by the MPEG-2/ ITU-T H.264 bit stream splicing device. This mechanism is not sufficient for achieving a reliable splicing operation because of the following reasons: Splicing devices cannot obtain any preceding information indicating the time schedule with regard to upcoming splice points where a s
43、eamless program insertion is ensured. In the case of a program insertion, synchronization of all PID streams, which constitute the program, cannot necessarily be established. Figure 1 shows the configuration of the splicing technique for the MPEG-2/ITU-T H.264 heterogeneous bit streams assumed in th
44、is Recommendation. In this figure, ENCAand ENCBare different types of video encoders, for example ENCAis MPEG-2 and ENCBis H.264, or vice versa. The transport mechanism of scheduling information is based on ITU-T J.181 with an extension defined in this Recommendation. In addition, constraints are re
45、quired for the seamless splicing of the heterogeneous bit streams. This Recommendation defines additional constraints on bit-stream splice points based on ITU-T J.189 and the desirable operation of the splicing device, which are required to achieve the seamless splicing. Figure 1 Configuration of se
46、amless splicing technique for the MPEG-2/ ITU-T H.264 heterogeneous bit streams J.189F01ENC A TS ( spliceable)Splicing deviceTS (spliceable)TS (spliceable)Scheduling(J.181)ENCB4 Rec. ITU-T J.286 (03/2009) 5.2 MPEG-2 Transport Stream syntax required for seamless splicing Clause 4.2 of ITU-T J.189+Cor
47、1 describes requirements on transport stream syntax for seamless splicing. This section identifies usage of relevant fields contained in an adaptation field of transport stream packet, i.e., splicing_point_flag, splice_countdown, seamless_splice_flag, splice_type and DTS_next_AU. The same requiremen
48、ts shall apply to transport stream syntax for seamless splicing defined in this Recommendation. See clause 4.2 of ITU-T J.189+Cor1 for further details. 5.3 Transport mechanism of scheduling information for splicing devices 5.3.1 Basic mechanism based on ITU-T J.181 The following descriptions are bas
49、ed on clause 4.3.1 of ITU-T J.189+Cor1 with some enhancements. Detailed information on a splicing event (the possible splice point, the PID of the spliced stream, the schedule of upcoming splicing events, etc.) can be mapped into a bit stream as the splice information section specified in ITU-T J.181. The splice information section notifies the splicing device of scheduled splice events prior to the arrival of splice points, and enables the splicing device to ensure a reliable splicing operation. The splice
