1、RP 21 7-2001 SMPTE RECOMMENDED PRACTICE Nonsynch ronized Mapping of KLV Packets into MPEG-2 Systems Streams 1 Scope This practice describes a means for mapping SMPTE metadata and other data essence, encoded in the SMPTE KLV protocol, into MPEG-2 systems streams. Use of synchronized streams and their
2、 syntax and semantics is beyond the scope of this practice. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this practice. At the time of publication, the editions indicated were valid. All standards are subject to rev
3、ision, and parties to agreements based on this practice are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. SMPTE 336M-2001, Television - Data Encoding Protocol using Key-Length-Value ITU-T H.222.0 / ISO/IEC 13818-1 :2000, Information T
4、echnology- Generic Coding of Moving Pictures and Associated Audio Information: Systems 3 Introduction This practice describes a means for mapping SMPTE metadata and/or essence encoded in the SMPTE 336M KLV protocol into MPEGQ systems streams. Astrong interest exists to carry audio/visual data, metad
5、ata, and/or essence multiplexed together within the same digital stream. The use of one data stream facilitates delivery of the overall multimedia presentation to the consumer. Metadata is classified as information about the content or essence. An example of metadata is information such as camera an
6、gle, scene identifier, or Pagel o 4 pages property rights. Other essence is supplemental content to the audio and video such as closed captioning, sports statistics, or hyperlinked advertisements. For some applications, it may not be appropriate for large amounts of data essence and metadata to be m
7、ixed together in the same stream. For example, applications intended for simple reaitime decoders may wish to carry data essence and metadata in separate streams using the specifications in this practice. 4 Transport and program stream mapping The MPEGQ systems specification describes a trans- port
8、stream and a program stream. The transport stream is tailored for communicating or storing one or more programs of coded video and other data in environments where significant errors may occur. Ex- amples include wireless communications, broadcast, and Internet delivery. Alternatively, the program s
9、tream is tailored for communicating or storing one program of coded video and other data in environ- ments where errors are very unlikely. Examples in- clude DVD, video archives, Intranet, and FTP. Both protocols allow for the multiplexing of other data with the audio and video stream. The MPEG-2 sy
10、stems stream protocol is primarily a methodology for multiplexing multiple streams of audio/visual/data information into a single program. Data may be carried in MPEG-2 systems streams similar to the way video and audio data are carried. The value of the ISOAEC 13818-1 stream-id field associated wit
11、h an SMPTE KLV program element shall be equal to OxBD (private-stream-1). - Copyright O 2001 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdaie Ave., White Plains, NY 10607 (914) 761-1100 Approved September 18,2001 RP 217-2001 4.1 Integration of KLV streams into a program 4.1
12、.1 Transport streams For transport streams, each KLV encoded stream shall be part of an MPEG-2 program and hence shall be listed asan entry in one ISO/IEC 13818-1 program in the program map table (PMT) for that program. Multiple KLV streams may belong to an MPEG-2 program. For each, the stream-typef
13、ield is set to PES private data (0x06). In addition, the program element loop in the PMTshall contain a registration-descriptor as defined in ISOAEC 1381 8-1, and the formatidentifierfield shall be set to Ox4B4C5641 (KLVA). As needed to aid in the discovery of KLV encoded streams and as allowed by M
14、PEGP systems, addi- tional descriptors may be included in the program element loop of the PMT, such as an association-tag. An example of the use of the association-fag is to allow the rediscovery of the program element carrying the KLV metadata after a PID remapping operation during remultiplexing.
15、4.1.2 Program streams In the case of a program stream, only one SMPTE KLV program element may be part of an MPEGP program stream since a program stream can only include one program element with a stream-id field value equal to OxBD. In the case when the program stream includes a program stream map (
16、PSM) conveyed in a PES packet with stream-idvalue OxBD, the descriptor loop of the PSM may include descriptors similar to the ones mentioned in 4.1.1. 4.2 PES encoding Each KLV item shall be placed into one or more PES packets. Multiple KLV items may be placed into a Annex A (informative) Organizati
17、on of references The organization of standards addressing essence and metadata is illustrated in figure A.l. No single standard can contain ail of the information needed to describe and encode essence and metadata. The encoding implementation standard (SMPTE 336M) and the metadata dictionary single
18、PES packet as long as they fit wholly in a single PES packet. The first KLV item in a PES packet shall be aligned with the beginning of the PES packet. Subsequent KLV items shall be appended without filler through to the size of the PES packet as adver- tised by the PES-packetlength field. If KLV it
19、ems are smaller than a PES packet, they shall not span multiple PES packets. NOTE - The term item applies herein to any individually coded KLV data including metadata and data essence components, data sets, and data packs as specified in SMPTE 336M. The value of the PS-packet/engfh field in the head
20、er of a PES packet conveying SMPTE KLV metadata shall be greater than zero. The value of the PTS-DTS-flags shall be set to 00, and the ESC-flag shall also be set to zero. The value of dafa-alignmentindiforshall be set as described below. 4.3 Segmentation A single KLV item may span more than one PES
21、packet. This shall be done for any KLV item that exceeds the maximum PES packet length (65535 minus headers). The afa-alignentindifor shall be set to one when the PES packet contains the beginning of a KLV item, and shall be set to zero othervise. Use of the da-alignmentindicatorfor this purpose is
22、allowed under ISO/IEC 13818-1 although it has in the past been used for video and audio packets. When a KLV item is segmented into more than one PES packet, all the PES packet segments of the item shall contain only the oneXLV item. Each KLV item is mapped into a single PES stream and shall not be s
23、plit onto multiple streams. When segmented KLV items are inserted into a single PES stream, the individual PES packets of different KLV items shall not be interleaved. standard (SMPTE 335M) form the SMPTE normative standards for metadata. Normative CMPTE documents, such as this one, supplement the s
24、tandards for encoding with examples and administrative instructions on managing the standardization and registration process. Page 2 of 4 pages RP 217-2001 I Essence or Metadata ipplication Layer Essence Type l. Essence Type 2,. m. Metadata Advanced Classes ag. MPEG7) Other Metadata Dictionaries . P
25、rotocol Layer Transport Layer Engineering Standards Figure A.l - Organization of references Page 3 of 4 pages RP 217-2001 Annex B (informative) Synchronized MPEG data streams This practice addresses only nonsynchronized MPEG streams and, thus, only the use of private-stream-1 sfream-id without PTS o
26、r DTS. The reason for this is that the design for full synchronization is complex and nontrivial when dealing with arbitrary KLV data items and is the sub- ject of future work. Annex C (informative) Bibliography SMPTE 335M-2001, Television - Metadata Dictionary Structure Page 4 of 4 pages Users are cautioned that private use of PTS or DTS may be incompatible with future applications or standards.
