1、RP 214-2002 SMPTE RECOMMENDED PRACTICE Packing KLV Encoded Metadata and Data Essence into SMPTE 291 M Ancillary Data Packets 1 Scope This practice describes a means for packing SMPTE rnetadata and data essence, encoded by the SMPTE KLV protocol, into SMPTE 291 M ancillary data packets for transport.
2、 Packing of KLV encoded metadata and data essence in this practice is defined only for a 10-bit SDI component video signal interface. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of public
3、ation, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. ANSVSMPTE 259M-1997, Television - 1 O-Bit 4:2:2 Compon
4、ent and 4fsc Composite Digital Signals - Serial Digital Interface SMPTE 291M-1998, Television - Ancillary Data Packet and Space Formatting SMPTE 292M-1998, Television - Bit-Serial Digital Interface for High-Definition Television Systems SMPTE 336M-2001, Television - Data Encoding Protocol Using Key-
5、Length-Value Proposed SMPTE RP 1682002, Definition of Vertical Interval Switching Point for Synchronous Video Switching Page 1 of 5 pages 3 Introduction This practice describes a means for packing SMPTE KLV encoded metadata and/or essence into SMPTE 291 M ancillary data packets. There is strong inte
6、rest in carrying audio/visual data, metadata, and/or essence, within the same digital stream. The use of one data stream facilitates delivery of the overall multimedia presentation. Metadata is classified as information about the essence. An example of rnetadata is information such as camera angle,
7、scene identifier, or property rights. Other information about the essence is supplemental content to the audio and video such as closed captioning, sports statistics, or hyperlinked advertisements. NOTE - ANSVSMPTE 272M and SMPTE 299M already define the carriage of embedded digital audio in ANSVSMPT
8、E 259M (SDI) and SMPTE 292M (HD-SDI), respectively. Carriage of data essence types in SMPTE 291 M ancillary data packets is under consideration. 4 Transport Packing Ancillary data may be present within the horizontal ancillaiy data space and the vertical ancillary data space of the ANSVSMPTE 259M or
9、 SMPTE 292M video signals. (Note that SMPTE 291M does not specify ancillary data packets over SMPTE 292M (HD-SDI), but thespecification is readily camed overto HD-SDI.) A possible data structure for a 10-bit ancillary data packet type 2 (ancillary packet type 2) carrying KLV encoded data is shown in
10、 figure 1 (informative). The KLV packet(s) shall be placed in the user data words of an ancillary data packet. The reader is urged to review SMPTE 291M for a detailed description of each field in the packet. Approved May 1,2002 Copyright O 2002 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEE
11、RS 595 W. Hartsdale Ave., White Plains, NY 10607 (914)761-1100 RP 214-2002 Inverse of Parity bit Paritybit, / KLV encoded data Ancillary DataID Secondary Data ID Data Flag Key Length Value Figure 1 - Possible data structure of an SMPTE 291M ancillary packet (type 2) carrying KLV encoded data NOTE -
12、Designers of equipment should be aware that KLV encoded data due to its 8-bit nature may be proc- essed and stored by 8-bit based equipment. The ANWSMPTE 259M interface supports 8- or 10-bit compo- nentvideo interfaces; however,forthis particular application only a 10-bit interface is defined. This
13、is due to the require- ment to maintain an unrestrained datacount (DC) fieldvalue which on an 8-bit interface would allow only user dataword lengths (length of KLV encoded data) divisible by four. 4.1 Ancillary packet DID and SDID for KLV encoded data The type of ancillary packets selected for the c
14、arriage of KLV encoded data is type 2. The data ID (DID) field of the ancillary packet carrying KLV-encoded metadata or data essence shall be set to 0x44. The secondary data ID (SDID) field is set to Ox04 for ancillary packets located in the vertical ancillary space and to 0x14 for anciliary packets
15、 located in HANC space (see figure 2 - normative). 4.2 Ancillary packet user data word (UDW) for KLV encoded data KLV data are defined in or multiple KLV coded packets; KLV coded Sets and Packs Ancillary Data Flag octets I Value Key Length I MID Message ID PSC Packet Sequence Count Figure 2 - Data s
16、tructure of (type 2) ancillary packet payload for carriage.of KLV encoded data including packet sequence count (segmentation system) 4.3 Location of metadata in vertical ancillary space In order to reduce the latency and buffering required for an ancillary data and KLV data reader, and to promote in
17、teroperability, ancillary packets containing KLV encoded metadata or data essence should be limited to a specific range of the total ancillary space, the vertical ancillary space. In addition, some metadata may be bound to a specific frame in order to be used. For those reasons, vertical ancillary d
18、ata packets carrying encoded KLV metadata packets shall, therefore, be placed within the VBI space. This space is defined in 525-line systems by the first line after the vertical switching point to the third line beforethestart of activevideoof avideoframeorfield. In a 625-line system, this space is
19、 defined by the first line after the vertical switching point to the last line beforethe start of activevideoof avideoframeorfield. NOTE - VANC space as defined in ANSWSMPTE 125 is intended for use of VANC data which are not synonymous with the ancillary packets carrying KLV encoded payload in the v
20、ertical ancillary space described in this practice. 4.3.1 Digital video interface systems at 525 and 625 lines SMPTE 291M ancillary data packets carrying metadata or data essence may be added to any line in the VBI VANC space as defined in 4.1 and SMPTE RP 168. Page 3 of 5 pages RP 214-2002 4.32 Dig
21、ital video interface systems at 750 and 11 25 lines SMPTE 291M ancillary data packets carrying metadata or data essence may be added to any line in the VBI VANC space as defined in 4.1 and SMPTE RP 168. NOTE - Users should be aware that other specifications might constrain the use of certain VBI lin
22、es for applications other than just carriage of metadata in ancillary data packets. 4.4 Location of metadata in HANC space When the location of metadata in ancillary space is not critical, data may be located in the HANC space allowed by SMPTE 291M. When the location of metadata is in the HANC space
23、, the secondary data ID (SDID) field of the ancillary packet carrying the metadata shall be set as defined in 4.1. NOTE - Users are cautioned that metadata inserted in HANC space defined in 4.1 may not be passed transpar- ently by all storage systems and some systems do not support ancillary packet
24、insertion in full compliance with SMPTE 291 M. 4.5 KLV encoded data segmentation KLV encoded data can reach a large size (up to 264 words) significantly exceeding data camage capabilii of single ancillary packets. Therefore, large KLV en- coded data must be placed into multiple ancillary packets. Th
25、e KLV segmentation process of this practice is applied to the transport level of a specific carrier as is SMPTE 291M ancillary data packet and space formatting. For uniformity reasons and to simplify payload segmentation and reassembly processes, all ancillary packets carrying KLV encoded data shall
26、 use the segmentation process defined in 4.5.1.1 and 4.5.1.2. The segmentation process is applied also to KLV encoded data shorter than 252 words. 4.5.1 Segmentation process Following the DID and SDID field of the ancillary packet header is the data count (DC) field. Each ancillary packet has the ca
27、pacity to carry a payload of 255 user data words (UDW). For the segmentation process of KLV encoded data, the first three user data words of the ancillary packet payload shall be used to form a segmentation system. The location of these words is shown in figure 2. 4.5.1.1 Message ID (MID) field The
28、first user word of the ancillary packet payload that follows the DC field defines a message ID (MID) field. This MID field identifies ancillary packets that carry information belonging to the same KLV encoded mes- sage. The message ID number increments with each different message with the first mess
29、age ID number being 1. NOTE - The segmentation system supports up to 255 different messages. The MID code value Ox00 is not sup- ported. 4.5.1.2 Packet sequence count (PSC) Two user data words immediately following the mes- sage ID (MID) field represent a packet sequence count (PSC). These two words
30、 form a 16-bit PSC number that defines the number of ancillary packets with the same MID value necessary to carry the KLV encoded message. The first data word of the PSC number represents the upper 8 bits and the second word of the PSC number represents the lower 8 bts of the 16-bit PSC number (bit
31、7 of the first word represents the MSB and bit O of the seocnd word represents the LSB of the PSC value). The PSC number is incremented with the value 1 assigned to a first ancillary packet containing the first part of a message NOTES 1 Eight-bit data payloads of an ancillary packet type 2, carried
32、over 1 O-bit systems interfaces, are mapped in such a way that bit b8 and bit b9 of the 10-bit data stream are set to parity and non-parity value, respectively. The parity en- compasses bit bO through bit b7 of the UDW. 2 The PSC number supports KLV message lengths up to (2l6Y252 octet words. Page 4
33、 of 5 pages . RP 214-2002 Annex A (informative) Bibliography ANSIISMPTE 125M-1995, Television - Component Video Signal 4:2:2 - Bit-Parallel Digital Interface ANSIISMPTE 299M-1997, Television - 24-Bit Digital Audio Format for HDTV Bit-Serial Interface ANSIISMPTE 272M-1994, Television - Formatting AESIEBU Audio and Auxiliary Data into Digital Video Ancil- lary Data Space SMPTE 334M-2000, Television - Vertical Ancillary Data Mapping for Bit-Serial Interface Page 5 of 5 pages
