1、STDmSMPTE 332M-ENGL 2000 8357V03 OOOgO72 LLb 9 SMPTE STANDARD SMPTE 332M-2000 for Television - Encapsulation of Data Packet Streams over SDTI (SDTI-PF) 1 Scope This standard specifies an open framework for encap- sulating data packet streams and associated control metadata over the SDTI transport (S
2、MPTE SM). Encapsulating data packet streams on SDTI allows them to be routed through conventional SDI (SMPTE 259M) equipment. This standard specifies a range of packet types which may be carried over SDTI. The range of packet types carried may be expanded as requirements develop. The standard does n
3、ot attempt to specify the payload contained in any packet. It offers options to add specific information to each individual packet including localized user data space, forward error correction (FEC), and a mechanism for accurate packet retiming at the decoder. The standard also offers a limited capa
4、bility for metadata to be added providing packet control infor- mation to aid the successful transfer of packets. The specification of the metadata follows the K-L-V approach of the SMPTE metadata dictionary and provides extensibility for future requirements. For easy reference, this standard is abb
5、reviated to the term SDTI-PF. This standard is limited to SDTI operating at a bit rate of 270 Mb/s and 360 Mb/s as defined by SMPTE 305M. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of pu
6、blication, the editions indicated were valid. All standards are subject to Page 1 of 9 pages 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. ANSUSMPTE 259M-7997, Television
7、- 1 O-Bit 4:2:2 Component and 4fc Composite Digital Signals - Serial Digital Interface SMPTE m5M-1998, Television - Serial Data Trans- port Interface SMPTE RP 168-1993, Definition of Vertical Interval Switching Point for Synchronous Video Switching 3 General specification Most packet streams do not
8、have critical timing requirements and a decoder can output packets in the order in which they were encoded, but with increased packet jitter resuiing from the buffering of packets onto SDTI lines. The result of the SDTI-PF packet encapsulation process is to introduce both delay and jitter to the pac
9、ket stream. However, MPEG-2 trans- port stream (MPEG-2 TS) packets are one case where a relatively small packet jitter specification is required to ensure minimal impact on MPEG-2 trans- port stream clock recovery and buffering circuits. This standard contains provisions to allow the packet jitter t
10、o be reduced to insignificant levels while the delay is an issue addressed by the method of packet buffering at the encoder. As a benchmark, the specification is defined so that a low packet jitter source, such as DVB-AS, can be carried through the SDTI-PF and be decoded to create an output with neg
11、ligible packet jitter. Although MPEG-2 TS packets are the most critical packet type for decodertiming accuracy, this standard CopyrCM02MY) by THECOCIEPIOF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. HaWaie Ave., white Plains, NY 10607 (914) 761-1100 Approved January 31,2000 STD=SMPTE 332M-ENGL 20
12、00 8357q02 OOOq093 052 E SMPTE 332M-2W also allows for other kinds of packets to be camed over the SDTI, with or without buffeting, to reduce packet jitter. Such packets may be ATM cells and packets based on the unidirectional internet protocol (Uni-IP). This standard provides several features for t
13、he carriage of packet streams such as: - A high packing density; - A flexible arrangement of data packet types and associated packet metadata; - Carriage of multiple channels of multiple data packet types; - Provisions for a powerful forward error correction (FEC) specification; - The ability to rep
14、roduce accurate data packet output timing; - The abii to add embedded user information. The control information associated with data packets can be used to: - Providea continuity counter to detect SDI switch- ing; - Provide a channel handle for transfers of multiple channels of data packets between
15、the same source and destination addresses; - Define the position of a data packet in a stream. 4 SDTI parameters SMPTE 35M specifies the SDTI for bit rates of 270 Mb/s and 360 Mb/s. Equipment may operate on only 270 Mb/s and still be compht with this standard. b7 bO The SDTI-PF uses the variable blo
16、ck mode of the SDTI as shown in figure 1. The separator and end code words are special 10-bit values defined in SMPTE 305M. All data in the space between the separator and end codes shall be 10-bit words where the data comprises 8 bits entered into bits bo to b7 of the 10-bii word, b8 shall be set t
17、o even parity of bits bo and b7, and b9 shall be set to odd parity. The block type word of the SDTI header shall be set to variable block mode according to SMPTE 305M. The SDTI data type word shall be set to the value 11 h indicatmg the data packet format (PF) variable bkck pay- load. This value sha
18、ll be registered in the data types table of SMPTE 305M as a 1 0-bt word of value 211 h. This standard shall not use the data extension facility of SMPTE 305M. 4.1 SDTI line and address numbers Since the data in each SDTI variable block may continue through as many lines as necessary until the block
19、end, it is necessary that the SDTI header line numbers are contiguous. It is also necessary that the SDTI header source and destination address values are constant throughout the transmission of all lines associated with any one SDTI variable block. 4.2 SDTI switching The arbitrary switching of SDTI
20、 data streams, althoughat the pictureframeboundary, may affect the abii to decode successfully the contents of the data packets without the use of special processing equip ment to mitigate the switching effects. The lines affected by a picture switch are defined in SMPTE RP 168. lt is recommended to
21、 avoid the use of the lines defined by SMPTE RP 168 together with the lines immediately prior to and following the switch line where transient conditions may occur. A continuity count can be provided to indicate variable blocks affected by a switch. Q) U o 5 o Data Block Word Count Figure 1 - Format
22、 of the SDn variable block Page 2 of 9 pages STD*SMPTE 332M-ENGL 21700 I8357903 0009099 T99 W 5 TLD block structure The data block area of each variable block shall be filled with one or more blocks defined by a type, length, and data (TLD) construct as shown in figure 2. The three components of the
23、 TLD construct are: - Type values in the range O1 h to OFh shall be used to identify TLD metadata blocks; - Type values in the range from loh to FFh shall use only the most significant 4 bits of the type word to identify TLD packet types. Thus, oniy 15 of these TLD types can be identified. - Type: T
24、he type of data contained in the value area as a local 1 -byte label; The least significant 4 bits Of type Words with a Vahe greater than OFh shall be defined as follows: - Length: The length of the value; and - Data: The data as defined by the type. Bit b3 shall be used to identify the presence of
25、an FEC at the end of the TLD data area. - If b3 = 1, then the FEC shall be present, else the FEC is not present and no space is allocated. Type is a single byte which identifies the type of data carried in TLD blocks. The type value may identify either one kind of TLD packet (such as an MPEG-2 TS pa
26、cket) or one kind of TLD metadata. Bit b2 shall be used to ident whether the data contain an embedded counter. When a TLD metadata blockis received, the metadata contained in the value area shall apply to all sub- sequent TLD packet blocks until either the end of the SDTI variable block or until a n
27、ew TLD metadata construct of the same type is received. The data from a TLD metadata block do not carry any significance across SDTI variable blocks, so each new variable block shall carry a new set of TLD metadata as needed (see figure 3). The data block area of each SDTI variable block shall be fi
28、lled wholly with TLD blocks. There shall be no padding either at the start of the SDTI data block, between TLD blocks, or between the end of the last TLD block and the SDTI end code. 5.1 TLDtype - If b2 = 1, then the embedded counter is present, else the embedded counter is not present and no space
29、is allocated. Bits bl and bo form a binary value in the range O to 3. - if the value = 3, then 6 user bytes are contained at the head of the TLD data area; - If the value = 2, then 4 user bytes are contained at the head of the TLD data area; - If the value = 1, then 2 user bytes are contained at the
30、 head of the TLD data area; - If the value = O, then no user bytes are contained at the head of the TLD data area. The TLD type is a 1 -byte word used to identify the type of data in the TLD block. The following rules shall be applied to the assignment of type values: 5.2 TLD length The length of a
31、TLD block specifies the length of the TLD data. Thus the length value can be used to skip to the next nD block if needed. - Atype value of t shall not be used; c Figure 2 - TLD blocks STDDSMPTE 332M-ENGL 2000 m 8357901 0009095 925 m SMPTE 332Y-2OOO Word Count I 1 I I l I I I I a I TLDBlock3 I TLDBlo
32、ck4 s I I I I l I U TLD Block 1 TLD Block 2 I I l I 5 TLD Block Figure 3 - Hierarchy of SDTI variable blocks and TLD blocks The TLD length shall be a variable length word defined as follows: - If the value of the first byte lies in the range OOh to FEh, then the length is given by the value of the f
33、irst byte; - If the value of the first byte is equal to FFh, then the length value is contained in the 2 bytes which immediately follow. Thus, TLD constructs with data blocks having a length greater than 254 bytes result in a length of 3 bytes of which the first byte is equal to the value of FFh and
34、 the next two bytes contain a length whose value may range from OOOOh to FFFEh. The 3-byte length value of FFFFFFh is reserved for future possible expansion. - User data of length O, 2,4, or 6 bytes. The length of the user data shall be defined by bits bo and bl of the type word; - A minor count val
35、ue in combination with a major count value giving 3 bytes which can be used to retime the data packets at the decoder output with negligible jitter; - A Reed-Solomon forward error correction (RS- FEC) of 6 bytes length. The TLD packet is shown in figure 4. At its simplest level, a data packet with a
36、 TLD type identifier which has the four LSBs set to O becomes a simple data packet containing only the packet data and no extra components. 5.3.1 User data area 5.3 TLD block TLD blocks defined by a type value up to OFh contain metadata of a format defined in SMPTE 331 M. TLD blocks defined by a typ
37、e value above OFh contain data packets as defined in the packet definitions. A data packet may be formed from the following components: User data space is defined in increments of 2 bytes allowing O, 2, 4, or 6 bytes of user data area. The contents of the user data area are private data not defined
38、in this standard. 5.39 Packet timing counter The combination of major and minor count values forms the packet timing counter with integer and c Page 4 of 9 pages STDDSMPTE 332M-ENGL 2000 835790% 000907b Bbl SMPTE 332M-2 - In the case of 360 Mb/s SDTI, the minor count value is loaded from a counter c
39、locked by a 36-MHz clock (which is at a higher rate than the MPEG-2 TS PCR) and counts over the range 0-15 to create a 2.25-MHz clock period, - The number of bits available in the minor count word allows SDTI word clock rates up to 576 MHz. Annex Adescribes how the packet timing counter can be used
40、for accurate output timing control. 5.3.2.1 Minor count The - 1: the TLD block contains a sequence head packet which is any packet which precedes the sequence start packet (e.g., preroll packets); - 2: the TLD block contains a sequence start packet which is the first packet of a sequence; - 3: the T
41、LD block contains a midsequence packet which is any packet between the sequence start and sequence end packets; - 4: the TLD block contains a sequence end packet which is the last packet of a sequence; - 5: the TLD block contains a sequence tail packet which is any packet whiih follow st hesequence
42、end packet (e.g., postroll packets); - 6: the TLD block contains both a sequence start packet and sequence end packet signifying a sequence of length 1; - 7: reserved but undefined. Bits b7 to b3 are reserved but undefined. 6.2 TLD packet definitions NOTE - At the time of publication, there is no gl
43、obal dictionary for data packet types so the following packet types are defined only by the local TLD type word. Global data packet labels may be added in a future version of this standard if a global data packet dictionary is published. 6.2.1 MPEGQ transport streams Type value: 8xh. Length variable
44、 depending on the presence and type of embedded FEC together with the presence of user, count, and FEC components. MPEG-2 transport stream (MPEG-2 TS) packets are 188 bytes in length. If fonvard error correction (FEC) has been added, then the packet length is increased to 204 bytesfor DVB emission a
45、nd 208 bytes for ATSC emission. The MPEG-2 TS FEC may be interleaved across packets and is designed for high levels of data loss through transmission systems which may intro- duce error bursts. Although in extreme cases SDTI can create occasional errors, the MPEG-2 TS FEC is unsuitable for correctin
46、g SDTi errors due to the inter- leave length, and this FEC will not exist if the packets carried are only 188 bytes in length. Consequently, the SDTI-PF format includes an optional noninterleaved FEC to correct for any errors which may occurthrough the SDTI link. Figures 5a, 5b, and 5c illustrate MP
47、EG-TS packets with different FEC capabilities. It is permissible for SDTI-PF blocks to use all three services - user data, retiming, and RS-FEC - as needed. STDOSMPTE 332M-ENGL 2000 m 8357903 OOOLiO99 570 D/ bo, SMPTE 332M-2W FEC MPEG-2 Transport Stream (, ,20 bytes) , Packet (1 88 bytes) MPEG-2 Tra
48、nsport Stream Packet (188 bytes) D/ MPEG-2 Transport Stream Packet (1 88 bytes) bo #I I zero (, bytes) Figure 5a - MPEG-2 transport stream packet Figure 5b - MPEG-2 Transport stream packet with null FEC space Figure 5c - MPEG-2 Transport stream packet with active 16/20 byte FEC 6.22 SDTI-CP transmis
49、sion packets Type value: 9xh. Annex A (informative) Using the SDTI-PF TLD block counter The combination of the major and minor count values de- fines a TLD block count resolution at least as high as 27 MHz and with a repeat period of approximately 30 ms. On recep- tion of the first packet in a sequence, the decoder may output the packet whenever the output buffer is ready and, at the same time, sets an internal counter running at the SDTI word clock rate (27 or36 MHz) based on the TLD block counter values. This counter operates in the same manner as defined for the major a
