1、 The attached document is a Registered Disclosure Document prepared by the proponent identified below. It has been examined by the appropriate SMPTE Technology Committee and is believed to contain adequate information to satisfy the objectives defined in the Scope, and to be technically consistent.
2、This document is NOT a Standard, Recommended Practice or Engineering Guideline, and does NOT imply a finding or representation of the Society. Errors in this document should be reported to the proponent identified below, with a copy to engsmpte.org. All other inquiries in respect of this document, i
3、ncluding inquiries as to intellectual property requirements that may be attached to use of the disclosed technology, should be addressed to the proponent identified below. Proponent contact information: Mr Roger Bunch Director of Engineering Free TV Australia 44 Avenue Road Mosman, N.S.W. 2088 Austr
4、alia Email: .au Page 1 of 11 pages RDD 8-2008Revision of RDD 8-2006 Copyright 2008 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved September 17, 2008 SMPTE REGISTERED DISCLOSURE DOCUMENT Storage and Distribution of Teletext Su
5、btitles and VBI Data for High-Definition Television RDD 8-2008 Page 2 of 11 pages 1 Scope Free TV Operational Practice OP-47 describes the technical/operational practices associated with the storage and distribution of closed caption/subtitling data in the vertical ancillary space of the 10-bit seri
6、al HD-SDI signal complying with ITU-R BT.1120-7. NOTE This document does not deal with the technical specifications of the actual closed captions/subtitles. It is intended to ensure that closed captioned/subtitled high-definition program material, in accordance with the appropriate Australian and in
7、ternational standards, will be successfully delivered to end users via the broadcasters storage and distribution processes. Additional to storage and distribution of subtitles, this operational practice describes the use of other ancillary data such as wide screen signaling (WSS) information via a m
8、ulti-packet solution. 2 Background The legislated requirements of digital broadcasting in Australia have prompted an increase in the number of captioned programs. Legacy closed caption data is currently distributed as World System Teletext (WST) subtitles in the vertical interval lines 21/334 of the
9、 SD (standard definition) bit serial video stream. The technical standard for closed caption/subtitling teletext data is ITU-R BT. 653-3 System B (refer to Section 8 Referenced Standards). In addition, where teletext based subtitles are required to be encoded for DTTB transmissions, this operational
10、 practice references ETSI EN 300 472, Specification for Conveying ITU-R System B Teletext in DVB Bitstreams. As TV networks distribution and recording/storage systems migrate to digital technology, appropriate technical and operational practices are required to ensure that program material which is
11、produced in accordance with the internationally recognized standards is delivered successfully to the viewing audience via the broadcasters analog and digital transmissions. This operational practice is consistent with SMPTE 334M. In particular, SMPTE 344M provides that the VANC data shall be carrie
12、d in the Y stream. 3 Definition of Terms The following definitions are consistent with SMPTE 291M. 3.1 Ancillary Data Flag (ADF): An ancillary data flag (ADF) marks the beginning of the ancillary packet. 3.2 Data ID (DID): A data identification word (DID) which defines the use of the user data forma
13、t carried in the ancillary packets user data words. 3.3 Secondary Data ID (SDID): Type 2 data identification uses a two-word data identification; defined as a combination of data ID (DID) and secondary data ID (SDID). A secondary data identification word (SDID) is part of the type 2 data identificat
14、ion format. 3.4 Data count (DC): A data count number word (DC) which defines the quantity of user data words in the ancillary packet. 3.5 User Data Words (UDW) : The user data words (UDW) of up to 255 words in each ancillary packet where the user data format is defined in a specific application docu
15、ment. 3.6 Checksum (CS): The checksum word (CS) is used to determine the validity of the ancillary data packet from the data identification (DID) word through the user data words (UDW). RDD 8-2008 Page 3 of 11 pages 4 Vertical Ancillary Data Packet 4.1 Type 2 Ancillary Data Packet Format The VANC da
16、ta packets which carry the WST (teletext) subtitles in the HD-SDI bit stream are located in the active line portion of one or more lines in the vertical ancillary space. Data may be located in any lines in the area from the second line, after the line specified for switching, to the last line before
17、 active video, inclusively. Each data packet follows the format defined in SMPTE 291M or ITU-R BT.1364 for a Type 2 ANC data packet. It consists of: the ancillary data flag (ADF), the data ID (DID), the secondary data ID (SDID), the data count (DC), the user data words (UDW), and the checksum (CS).
18、The Type 2 Ancillary Data Packet is diagrammatically represented in figure 1. Figure 1 Type 2 Ancillary Data Packet RDD 8-2008 Page 4 of 11 pages 4.2 Technical Characteristics of the Type 2 Ancillary Data Packet Format The technical characteristics of the Type 2 Ancillary Data Packet format are as f
19、ollows: (i) The ADF has the value 000h 3FFh 3FFh. (ii) The VANC WST packet shall be known as the Subtitling Distribution Packet (SDP) with DID and SDID values 143h and 102h, respectively (includes parity). These are also the DID and SDID values when the SDP is transported as an “inner” packet of the
20、 Multipacket described in clause 6. (iii) The VANC Multipacket is for the carriage of a combination of subtitling packets and other ancillary data, such as WSS data packets, and shall have DID and SDID values 143h and 203h, respectively (includes parity). (iv) WSS data packets shall have DID and SDI
21、D values 250h and 101h, respectively, and can be transported as an “inner” packet within a VANC multipacket. (v) The UDW data words consist of 8-bit data bytes, which are transmitted in bits b7 b0 of the 10-bit data word. Bit b8 is even parity for b7 through b0, and b9 = not b8. The data payload for
22、 each service is inserted into the UDW of the ANC packet as 10-bit words. The number of words is indicated in the DC field of the ANC packet header. (vi) The UDW component of the packets must not exceed 255 words in length (refer to clause 3.11.2 of SMPTE 291M). (vii) Other VANC ancillary data packe
23、ts may be required and, therefore, this document may need to define additional SDID and DID values in the future. 5 Subtitling Distribution Packet (SDP) Format The Subtitling Distribution Packet (SDP), as described in figure 2, consists of a standard ANC header and a UDW payload capable of carrying
24、five (5) packets of the equivalent “vertical interval lines” of WST (teletext) subtitling in the following structure whose UDW size cannot exceed 255 words. 5.1 Syntax of the Subtitling Distribution Packet The syntax of the subtitling distribution packet is defined as follows: Header: ADF (3 words)
25、DID (143h) SDID (102h) DC = (1 word) variable value (as per SMPTE 291M or ITU-R BT.1364) UDW: IDENTIFIER (151h) IDENTIFIER (115h) LENGTH (total number of words, from the first IDENTIFIER through to SDP CHECKSUM, inclusive.) FORMAT CODE = 102h, identifying this as WST teletext subtitles DATA ADAPTION
26、 HEADER fixed length 5 words VBI Packet 1 Descriptor word Field/Line Packet Descriptor Structure A (as defined following) VBI Packet 2 Descriptor word Field/Line Packet Descriptor Structure A (as defined following) RDD 8-2008 Page 5 of 11 pages VBI Packet 3 Descriptor word Field/Line Packet Descript
27、or Structure A (as defined following) VBI Packet 4 Descriptor word Field/Line Packet Descriptor Structure A (as defined following) VBI Packet 5 Descriptor word Field/Line Packet Descriptor Structure A (as defined following) if (VBI Packet 1 Descriptor ! = 0) Packet Descriptor Structure B (as defined
28、 following) if (VBI Packet 2 descriptor ! = 0) Packet Descriptor Structure B (as defined following) if (VBI Packet 3 descriptor ! = 0) Packet Descriptor Structure B (as defined following) if (VBI Packet 4 descriptor ! = 0) Packet Descriptor Structure B (as defined following) if (VBI Packet 5 descrip
29、tor ! = 0) Packet Descriptor Structure B (as defined following) FOOTER ID (274h) FOOTER SEQUENCE COUNTER (2 words) (see explanation following) SDP CHECKSUM (see explanation following) CS (as per SMPTE 291M) 5.2 Footer Sequence Counter The Footer Sequence Counter (FSC) is a 16-bit unsigned integer wh
30、ich is set to the value of 1 plus the value of the Footer Sequence Counter in the previous SDP, with the value of the counter wrapping from 65535 to 0. The first word transmitted contains the 8 most significant bits of the 16-bit value and the second word transmitted contains the 8 least significant
31、 bits. Bits 8 and 9 of each word contain the parity bits calculated in the same manner as the UDW data words. 5.3 Subtitling Distribution Packet CheckSum The SDP CheckSum is the 8-bit value required to make the arithmetic sum of the entire received packet (from the first byte of the identifier up to
32、 the SDP CheckSum, inclusive) modulo 256, equal to zero. After the 8-bit value is calculated, parity bits 8 and 9 should be calculated in the same manner as other UDW data words. 5.4 Packet Descriptor Structure A The SDP has five (5) Packet Descriptor A words. 5.4.1 Syntax of the Packet Descriptor S
33、tructure A The syntax of Packet Descriptor Structure A is defined as follows: Packet Descriptor Structure A bits b0 to b4 are line no (range 0 and 6 to 22 for SD video VBI line) bits b5 and b6 reserved (set to 0 if no VBI line in this position) bit b7 is field no (0 = even field, 1 = odd field) bits
34、 b8 and b9 are even and odd parity as per UDW data format section 4.2 NOTE Structure B emulates ITU-R System B Teletext VBI line RDD 8-2008 Page 6 of 11 pages Figure 2 Subtitling Distribution Packet RDD 8-2008 Page 7 of 11 pages 5.4.2 Semantics of the Packet Descriptor Structure A The semantics of P
35、acket Descriptor Structure A is as follows: When bits b0 to b7 of any VBI Packet n descriptor are all set to 0, this indicates that there is no packet data present for that position. The values of bits b5 and b6 of the packet descriptor are reserved and shall be set to zero if there is no correspond
36、ing packet. Packets sent in this way are transmitted in exact sequence; thus, if a field number encountered is different from the previous field number, then the device will “wait” for the correct field to insert the data. If a further field change is encountered, the device must “wait” for the next
37、 field rather than insert the data into a previous field. Line numbers should increase within field; a device may ignore lines out of order. It is possible to transmit illegal line number values and decode devices may choose to ignore these lines; however, the associated Structure B space allocation
38、 must be transmitted if this Structure A word is transmitted. If VBI Packet descriptor n is not present, then all following VBI Packet descriptors shall be set to 0. 5.5 Packet Descriptor Structure B The five Packet Descriptor Structure A words are then followed by five Packet Descriptor Structure B
39、 units. 5.5.1 Packet Descriptor Structure B The Packet Descriptor Structure B units contain the standard WST (System B teletext) 45 byte packet. 5.5.2 Syntax of the Packet Descriptor Structure B The syntax is defined as follows: Packet Descriptor Structure B run-in code two words containing (255h) e
40、ach framing code (227h) MRAG two words as required including hamming protection + bits b8 and b9 parity (refer to ITU-R BT 653-3) subtitling data 40 words including parity (refer ITU-R BT.653-3) 6 Vertical Ancillary Multipacket Format The VANC Multipacket is a Type 2 ancillary data packet as defined
41、 in SMPTE 291M or ITU-R BT.1364 and has DID and SDID values of 143h and 203h, respectively. Only one UDW data payload block should be used to emulate the “single packet” requirement limitation of some storage devices. The UDW payload of this Multipacket consists of one (1) priority word, followed by
42、 one or more separate inner packets having a defined Type 2 DID/SDID definition pair and cannot exceed 255 words. 6.1 Syntax of the VANC Multipacket The syntax of the VANC Multipacket is defined as follows: Header: ADF (3 words) DID (143h) SDID (203h) DC = (1 word) variable value (as per SMPTE 291M
43、or ITU-R BT.1364) RDD 8-2008 Page 8 of 11 pages UDW: PRIORITY (1 word). The number of the packet that has priority, for future use) for (i=0;iN; i+) LINE/FIELD (1 word) (VANC field and line no. see below) NDID (xxxh) NSDID (yyyh) NDC (1 word) value variable (per SMPTE 291M or ITU-R BT.1364) NUDW Var
44、iable as per UDW data payload words above CS (as per SMPTE 291M) 6.2 Semantics of the VANC Multipacket The semantics of the VANC Multipacket is defined as follows: The LINE/FIELD word consists of bits b0 to b4 (b0 LSB) representing VANC line no. bit b5 is field no. (o = even field, 1 = odd field) bi
45、ts b6 and b7 unused and set to zero bits b8 and b9 are even and odd parity as per UDW data format section 4.2 The values xxxh and yyyh above will be 143h and 102h respectively for WST SDP packet and 250h and 101h for WSS packet. The total number of words in the multipacket structure, from the PRIORI
46、TY word to the NCS word of the last inner packet, inclusive, must not exceed 255. If the multipacket contains such inner packets which contain data that is required to maintain relative frame sync it would be desirable to insert the multipacket on field 1 in the case where a storage device may delay
47、 the video one field. RDD 8-2008 Page 9 of 11 pages Figure 3 Multipacket Structure RDD 8-2008 Page 10 of 11 pages 7 Video and Audio Timing There is no specific provision in this operational practice for ensuring that the relative timing between the video and its embedded VANC data is correct. The on
48、ly timing relationship that exists is created when the data is embedded in the video. Once that relationship is established, the deterministic nature of the ITU-R 1364-1 serial bit stream and the SMPTE 291M ANC packets ensures that the relationship is preserved. 8 Interlace Field Designation It shou
49、ld be noted that interlace field designations are sometimes referred to as odd and even fields, or field one and field two. In the case of this document, field one is the odd field, and field two is the even field. 9 Referenced Standards ETSI ETS 300 706 Ed. 1 (1997-05) “Enhanced Teletext Specification“ EN 300 472 V1.2.2 (1997-08) Digital Video Broadcasting (DVB) Specification for Conveying ITU-R System B Teletext in DVB Bitstreams. ITU Rec ITU-R BT.653-3 1998 Annex 1 “Characteristics of Teletext Systems“ Rec ITU-
