1、STD=SflPTE 3LSM-ENGL 2000 m 8357403 OOOLiOOS 3b9 SMPTE STANDARD SMPTE 319M=2000 for Television - Transporting MPEG-2 Recoding Information through 4:2:2 Component Digital Interfaces Contents Scope Normative references General Definitions MPEG-2 recoding information Macroblock rate information MPEG-2
2、recoding information transport mechanism Picture rate information Scope This standard specifies an embedded transport mechanism for the MPEG-2 recoding data set as defined in SMPTE 327M for the representation of MPEG-2 recoding information in IT-R BT.656,4:2:2 component digital interfaces. The recod
3、ing data set is derived from an ISO/IEC 13818-1 and 2 compliant MPEG bit stream during the decoding process, as described in ISO/IEC 1381 8-1 and -2. For the minimum operation of this standard, the MPEG-2 recoding data set shall be spatiaiiy and temporally aligned to each decoded macroblock mapped i
4、nto an ITU-R BT.656 interface. This standard specifies the spatially and tempo- rally aligned transport of the MPEG-2 recoding data set within the active picture area on ITU-R BT.656 interfaces for equipment that complies with ISO/IEC 13818-1 and -2, including 422PML and MPQML for both the 625/50 an
5、d 525/60 video standards. Page 1 of 11 pages 2 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and pa
6、rties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. SMPTE 327M-2000, Television - MPEG-2 Recoding Data Set ITU-R BT.601-5 (1 994), Studio Encoding Parameters of Digital Television for Standard
7、4:3 and Wide-Screen 16:9 Aspect Ratios ITU-R BT.656-4, Interfaces for Digital Component Video Signals in 525-Line and 625-Line Television Systems Operating at the 4:2:2 Level of Recommen- dation IT-R BT.601 Part A ITU-T H.222.0 with amend 1-2, ISOAEC 13818- 1 :1996, Information Technology - Generic
8、Coding of Moving Pictures and Associated Audio Information: Systems ITU-T H.262 with amend l/corr 1 and amend 2/corr 2, ISO/IEC 13818-21996, Information Technology - Generic Coding of Moving Pictures and Associated Audio Information: Video 3 General The principal application of this standard is to p
9、re- serve the quality of the video signal when cascading Copyright O 2000 by ME SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., white Plains, NY 10607 (914) 761-1 100 SYPTE 319M-2000 MPEG-2 decoders and coders for editing or transcod- ing purposes by feeding forward previou
10、s coding decisions. The transport mechanism for the MPEG-2 recoding data set permits the simultaneous processing of both the video and the MPEG-2 recoding data set and, consequently, of the MPEG bit stream. This allows lossless cascading, frame accurate editing, and logokaption insertion to be perfo
11、rmed. The information contained in the MPEG-2 recoding data set is defined in SMPTE 327M. This recoding information shall be temporally locked to the decoded (or partially decoded) video to the nearest MPEG-2 frame or field depending on the picture structure of the coded MPEG-2 bit stream. It shall
12、also be spatially locked with the decoded video to the nearest MPEGQ macroblock within the decoded frame/field. To accrue the full benefits of the recoding information when cascading via a 42:2 component digital inter- face, the following recommendationsshall be adhered to: - The transporation mecha
13、nism shall preserve at least the 8 most significant bits of active video. The mechanism outlined uses the least significant bt of each 1Wit chrominance sample to transmit the data through the ITU-R BT.656 interface. - It is also necessary for the recoding information to be aligned with the decoded M
14、PEG macroblocks in the decoded pictures, both spatially and tempo- rally. This standard is based on producing an ITU-R BT.656 output and will cover MPEG bit stream up to and including 422POML and MPBML for both 625/50 and 525/60 systems. NOTE - Users should be aware that some existing equip- ment us
15、ing ITU-R 81.656 interfaces alters or uses the tenth bit of the video samples for other (nonstandardized) pur- poses. Where this occurs, the recoder will be unable to benefit from the MPEG-2 recoding information. 4 Definitions 4.1 aligned: Applied usually to recoding informa- tion arranged so that i
16、nformation relating to a macroblock (or other region) is embedded within that region of the decoded signal. 4.2 bitstream: An ordered series of bits con- forming to ISO/IEC 13818-2. 4.3 bottom field: One of two fields that comprise a frame. Each line of a bottom field is spatially located immediatel
17、y below the corresponding line of the top field. 4.4 cascading: The process where video that has once been coded (compressed) is sub- sequently decoded and coded once more. This cascaded step could carry on for any number of generations. 4.5 chrominance: The color-difference samples defined in ITU-R
18、 BT.601. 4.6 coding: The process by which an uncom- pressed video sequence is compressed to a bit stream that conforms to ISOAEC 13818-2. 4.7 column: A vertical column of macroblocks spanning the full height of the decoded picture (columns are numbered from left to right starting at zero). 4.8 CRC:
19、Cyclic Redundancy Check. A class of error detecting codes used in this standard to detect errors when the recoding information and the decoded pictures are being edited or proc- essed in an ITU-R BT.601 stream by external equipment . 4.9 decodedvideo,decodedpichire: Output video generated by an ISO/
20、IEC 1381 8-2 compliant decoder that complies with the ITU-R BT.656 interface standard. 4.10 decoder: A compressed bit stream decoder that complies with ISOAEC 13818-2. 4.11 DTS: Decoder Time Stamp (see ISO/IEC 13818-1). 4.12 embedded: Applied usually to recoding in- formation conveyed within a digit
21、al video signal so as to be capable of being passed through digital video equipment. 4.13 macroblock Defined in ISO/IEC 13818-2 as a block of 16 x 16 luminance pixels. Paga 2 of 11 pages SMPTE 319M- 4.14 macroblock rate information: This corre- sponds to the coding information from the individual ma
22、croblocks as defined in this stand- ard. 5 MPEG-2 recoding information ISO/IEC 1381 8-2 bit stream that relates to the MPEG-2 recoding information comprises: - The elements defined in SMPTE 327M. 4.15 MPEG profileAevel: As defined in ISO/IEC 1381 8-2. - Additional elements from both macroblock and p
23、icture rate information as described in this standard. 4.18 picture rate information: This corresponds to the coding information from the ISO/IEC 13818-2 bit stream that relates to the whole picture as defined in this standard. 4.19 PTS: Presentation Time Stamp (see ISO/IEC 13818-1). 4.20 recoding d
24、ata set: The set of information defined in SMPTE 327M. 6 Macroblock rate information The contents of the MPEG-2 recoding data set relat- ing to each macroblock will be spatially as well as temporally aligned with the decoded video pixels relating to that macroblock. The elements in table 1 are at pi
25、cture rate in the MPEG-2 stream, but are inserted into MPEG-2 recod- ing information at both picture and macroblock level to create the alignment required to allow editing of the resukant ITU-R BT.601 signal. 4.21 stripe: A horizontal row of macroblocks spanning the full width of the decoded picture
26、 (stripes are numbered from top to bottom start- ing at zero). The elements in table 2 are required in the transport mechanism to synchronize the video information and the MPEG-2 recoding information. enable transparent recoding (in a mathematical sense) of the video signal. 7 MPEG-2 recoding inform
27、ation trans- port mechanism 4.23 top field: One of two fields that comprise a frame. Each line of a top field is spatially located immediately above the corresponding line of the bottom field. This comprises 256 bits of data per macroblock that shall be placed bit by bit onto the least significant b
28、it of each 10-bit chrominance sample in the decoded video. 4.24 transcoding: A COnVeSiOn within the The decoded 4:2:2 component ,ideo macroblock MPEG-2 stream domain, such as bit rate Chang- conesponds to a matfoc of 16 16 luminance compo- ing Or changing the group Of pictures nents and two matrices
29、 of 8 x 16 colordifference components. Hence, in total there are 256 pixels of structure. luminance and 256 pixels of chrominance in each 4.25 video: A signal conforming to ITU-R macroblock. In ITlJ-R BT.656 video, the multiplexed BT.601 in this standard. order for these pixels is Cb,Y,C,Y, etc. Pag
30、e 3 of 11 pages Line Frame Feld Cod Coding O O 1 2 1 3 4 5 2 6 7 3 8 9 4 10 11 5 12 13 6 7 14 15 Figure 1- Macroblock format of MPEGQ recoding information Page 4 ot 11 pages Table 1 - Additional macroblock rate information I Parameter t opf i e I df i rs t No. of bits 1-bit flag Definit ion I repeat
31、first-field 422-420-c hroma picrate-element picrate-element31:16 picrate-elementl5:0 q-scale-type reserved Set to a value equal to top-fielhfirst held in the stream and also indicates, alona with reoeat-first field. the temporal alignment of the recoding information with its associated video. Set to
32、 a value equal to repeat-firstfield held in the original bit stream. The contents of the recoding information of the first field must also be repeated, as indicated by this flag. A value of O indicates the bit stream was 4:2:0 and chromi- nance up-sampling was performed to output 4:2:2 video. A valu
33、e of O indicates the bit stream was 4:2:2 and no chromi- nance filtering was performed. Represents part of the picture rate information for the present picture and has its content dispersed within the decoded picture. This is defined in further detail in clause 8. Set to a value equal to q-scale-typ
34、e held in the original bit stream. These blocks have no meaning and all the bits shall be set to o. 1-bit flag 1-bit flag 16-bit ui 16-bit Ui 1 -bit flag Table 2 - Additional transport elements Parameter cribsync-code f r-fl-srib rolling-crib-mb-ref sri b-c rc srib-crc31:16 sri b-c rc 1 5: O No. of
35、bits 5-bit flag 1 -bit flag 16-bit i 16-bit Ui 16-bit Ui Definit ion This is a fixed bit-string, 11 11 1, which shall be used to indicate the left alignment of the first row of each macroblock. This flag shall be set to the value 1 when picture-structure is set to frame picture structure (value 11)
36、and indicates that the MPEG-2 recoding information is distributed over 16 frame lines. If picture-structure is not set to frame (value ll), then the flag is set to O and the recoding information is distributed over 16 field lines. This mechanism ensures that the recoding information remains spatiall
37、y and temporally locked to the corresponding pixels in the decoded video framedfields. The distribution of the recoding information for frame pictures and field pictures is further shown in figures 2 and 3. This is a 16-bit modulo 65521 rolling reference value (see note). This rolling reference incr
38、ements on every macroblock of the transmitted picture. The count shall be continuous across trans- mitted picture boundaries. This value shall be initialized at start-up to a number selectable between O and 65520 inclusive. This is to allow systems of decoders to be built with unique recoding inform
39、a- tion identifiers. A 32-bit CRC to allow error detection for each macroblock of the MPEG-2 recoding information. A model for the operation of this 32-bit CRC is defined in annex A of ISO/IEC 13818-1. The CRC is calculated on the 224 data bits of the macroblock of MPEG-2 recoding information taken
40、in raster order, using the following generator polynomial: x= +P + xn +P + Xl6 + xl* + Xl +x*+X8 +x7 +x5 + x4 +xL + x + . NOTE - The largest 16-bit derived prime number was chosen to ensure that there is a minimum coherence between the position of the macroblock and its equivalent address in subsequ
41、ent pictures. Page 5 Of 11 pages STD-SMPTE 319M-ENGL ZU00 = 8357903 Il004014 72b top field O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 top field O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 bottom field 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 battom field 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Stripe O Column O Str
42、ipe 1 Column 1 Odd lines of macroblock format i/ Re-Coding information 2 Even lines of macroblock format ReCoding Information Figure 2- Recoding information in frame coded pictures (fr-fl-snb=l) Stripe O Column O Macroblock format Recoding Information for Bottom Field Macroblock format Re-Coding Inf
43、ormation for Tcp Field 1 Figure 3- Recoding information in field coded pictures (fr-fl-sribdJ) Page 6 of 11 pages STD=SflPTE 3LSM-ENGL 2000 D 8357403 OOOLiDLS bb2 To increase the resilience of the detection of edits in the macroblock formatted recoding information, a form of pari scrambling is appli
44、ed to the data before being placed in the least significant bit of the 10-bit chrominance samples. The parity scrambling scheme used is shown in figure 4, where the bits represent the bits of 1 O-bit video (i.e., bits 2 through 9 correspond to the 8-bit video). Consider the first few video samples i
45、n a stream as being CbO, YO, CP, Y1, Cbl, Y2, Crl, Y3, etc. The pari for scrambling the macroblock formatted recod- ing information inserted into each chrominance sam- ple is derived by combining the parity of the chrominance sample with the parity of the subsequent luminance sample in the video str
46、eam. For example, the parity used to scramble the macro- block formatted recoding information for sample CbO above is the combined par of CbO and YO, the scrambling of data for Ca is taken from the combined parity of CP and Y1, etc. A detailed example of the macroblock formatted re- coding informati
47、on bits encoded into the ITU-R BT.656 samples for the first four luminance and associated chrominance samples is shown in table 3. 8 Picture rate information This clause defines the picture rate information re- quired in the recoding information. Table 4 shows the elements which must be included. Th
48、e picture rate information must all pass without error in order to achieve the best performance when recoding. Therefore, the picture rate information must be sent in a reasonably rugged way and it is for this reason that several copies are sent in the macroblock formatted recoding infomation distri
49、buted around the picture in the manner which will now be discussed. In order to carry the full picture rate information, 4320 bits are required. Each macroblock of recoding infor- mation shall cany a 32-bit element of this picture rate information which will therefore require a total of 135 macroblocks in oder to carry the full picture rate information. The number of copies which will then be distributed for the main picture types and video format is given in table 5. SMPTE 319M-2ooo Other formats also exist, for example, in 422POML, the formats 720 x 608 pels f
