1、SMPTE RECOMMENDED PRACTICE Ancillary Data Mapping over MPEG-2 Video Elementary Stream Editing Information RP 21 2-2002 Pagel of 4 pages 1 Scope This practice defines the mapping of vertical ancillary (V-ANC) data packets within MPEG-2 video elementary streams conforming to the framework provided by
2、SMPTE 328M. The purpose of this practice is to provide a method of mapping V-ANC data packets through the &bit interface provided by SMPTE 328M and to provide guidance for data coding to prevent the false creation of MPEG-2 video elementary stream start marker bit sequences. Although this practice r
3、efers to bit-serial interfaces, the desctiption can be equally applied to the equivalent parallel interfaces. 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 indi
4、cated were valid. All standards are subject to revision, 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 291 M-1998, Television -Ancillary Data Packet and Space Formatting SMPTE
5、 328M-2000, Television - MPEG-2 Video Elementary Stream Editing Information 3 General This practice defines the mapping of vertical ancillary (V-ANC) data packets within the framework provided by SMPTE 328M. SMPTE 291M defines the basic structure of ancillary data packets in the form of 10-bit words
6、. SMPTE 291M defines ancillary data packets for use in both the horizontal blanking interval (H-ANC) and the vertical blanking interval (V-ANC). This practice only provides a mapping for V-ANC data packets. V-ANC packets can cany many kinds of data including those defined in SMPTE 334M, SMPTE RP 214
7、, and other specifications which define V-ANC packet payloads. The MPEG-2 video elementary stream (video-ES) can be supplemented with additional information for professional studio applications according to SMPTE 328M. This supplementary information is carried within the sequence header and the user
8、 data area of the MPEG-2 video-ES to facilitate seamless edits under Copyright O 2002 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. HaMale Ave., White Plains, NY 10607 (914) 761-1100 Approved April 22,2002 RP 212-2002 circumstances defined in SMPTE 328M. This practice specifies th
9、at V-ANC packets be placed into the space assigned as ancillary data in the MPEG-ES syntax as defined by SMPTE 328M. The ancillary data are based on an %bit interface. The 10-bit word structure of SMPTE 291M is not appropriate for an 8-bit interface. While annex A of SMPTE 291 M provides guidance fo
10、r 8-bit operation, the result is unnecessarily restrictive and a simpler solution is defined in this practice. It should be noted that while the internal operation in the MPEG-2 video-ES stream is %bits, the input and output interfaces of SDI operate with the full 1 O-bit resolution. 4 Data structur
11、e The V-ANC data packet shall be mapped onto the ancillary data payload of the ES editing information as follows. a) The data-ID of the MPEG-ES syntax, as defined in SMPTE 328M, shall be set to the value 07h in conformance with that standard. b) The ADF (ancillary data flag) words of each SMPTE 291
12、M packet shall be mapped only from bits bO to b7. Bits b8 and b9 of the ADF shall be discarded. c) The DID, SDID/DBN, DC, and UDW words of SMPTE 291 M shall be mapped following the ADF. Bits b8 and b9 shall be discarded. d) The CS (checksum) word of SMPTE 291M shall be recalculated from the %bit DID
13、 word through the 8-bit UDW words with 8-bit accuracy. e) In compliance with SMPTE 291 M, the ancillary packets shall be mapped contiguously with each other into the payload area of the MPEG-ES-editing-information space as defined by SMPTE 328M. f) As the resulting 8-bit ancillary data bit-stream ma
14、y consist of more than 23 consecutive zeroes, a marker bit shall be inserted every 22 bits according to SMPTE 328M. g) If the value of ancillary data length in the MPEG-ES editing information is greater than the actual data length of all the packets, the unused bits shall be set to a value of 1. The
15、 full 10-bit V-ANC packet data structure shall be recreated at the output, including the recalculation of the 10-bit CS (checksum), to meet the 10-bit interface specification of SMPTE 291M. Figure 1 shows the input V-ANC data packet structure of this practice. V-ANC packets may be either type 1 or t
16、ype 2 as defined in SMPTE 291 M. Figure 2 shows the mapping of the V-ANC data packets to 8-bits and padded with marker bits as defined by SMPTE 328M. Page 2 of 4 pages RP 21 2-2002 1 V-ancillary line A V 4 packet 1 1- MSB b9 LSB bO Contents form Figure 1 - Input V-ANC data packet structure The check
17、sum is re-calculated from DID ES editing information 7 “1“ bits must be padded if the value of “ancillary_data-lengh“ in ES editing information is greater than actual data length of total packets. / Figure 2 - Mapping V-ANC data packets in conformance with SMPTE 328M Page 3 of 4 pages RP 212-2002 Annex A (informative) Bibliography SMPTE 334M-2000, Television - Vertical Ancillary Data Mapping for Bit-Serial Interface SMPTE RP 214, Packing KLV Encoded Metadata and Data Essence into SMPTE 291M Ancillary Data Packets Page 4 of 4 pages
