1、1 ScopeThis standard specifies a directory index to classifyvarious types of data to be recorded into the binarygroups (user bits) of the SMPTE time and controlcode. The directory index, located in two binarygroups of the time and control code frame, fully speci-fies the type of data stored in the r
2、emaining binarygroups of that frame.This standard also specifies the group assignmentsof timing, application, and control data types to sub-sets of the directory index. It applies to both linear andvertical interval time code applications. Specificationsof application dialects will be developed in r
3、elateddocuments.2 Normative referencesThe following documents contain provisions which,through reference in this text, constitute provisions ofthis standard. At the time of publication, the editionsindicated were valid. All standards are subject torevision, and parties to agreements based on thissta
4、ndard are encouraged to investigate the possibilityof applying the most recent edition of the documentsindicated below.ANSI/SMPTE 12M-1995, Television, Audio and Film- Time and Control Code SMPTE RP 169-1995, Television, Audio and FilmTime and Control Code - Auxiliary Time AddressData in Binary Grou
5、ps - Dialect Specification ofDirectory Index LocationsISO/IEC 646:1991, Information Technology - ISO7-Bit Coded Character Set for Information Inter-changeISO/IEC 2022:1994, Information Technology -Character Code Structure and Extension Tech-niques3 Data structure3.1 Frame format (see figure 1)3.1.1
6、Binary group labelsThe binary group containing the lowest frame addressbit numbers is referred to as binary group 1 (BG 1),and the binary group containing the highest bit num-bers is referred to as binary group 8 (BG 8). Within abinary group, the lowest bit number contains the leastsignificant bit o
7、f data.3.1.2 Binary byte labelsThe data content of the binary groups may be specifiedas 8-bit character sets, in which case the charactersshould be inserted in accordance with ANSI/SMPTE12M. Thus, binary groups 1 and 2 form binary byte 1,binary groups 3 and 4 form binary byte 2, binarygroups 5 and 6
8、 form binary byte 3, and binary groups7 and 8 form binary byte 4. Within a binary byte, thelower numbered binary group contains the four leastsignificant bits of data.3.1.3 Directory indexBinary groups 7 and 8 shall be used as a directoryindex for page-line user bit applications. Binary group8 shall
9、 specify a directory page totalling 16 pages, andbinary group 7 shall specify a directory line totalling16 lines per page.for Television, Audio and Film -Binary Groups of Timeand Control Codes -Storage and Transmission of DataCAUTION NOTICE: This Standard may be revised or withdrawn at any time. The
10、 procedures of the Standard Developer require that action be taken to reaffirm, revise,or withdraw this standard no later than five years from the date of publication. Purchasers of standards may receive current information on all standards by calling orwriting the Standard Developer. Printed in USA
11、.ANSI/SMPTE 262M-1995SMPTE STANDARDPage 1 of 5 pagesApprovedSeptember 12, 1995Copyright 1995 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS595 W. Hartsdale Ave., White Plains, NY 10607(914) 761-1100Figure 1 - Frame format (vertical interval and linear track)ANSI/SMPTE 262M-1995Page 2 of 5
12、 pages3.2 Directory index format (see figure 2)3.2.1 Time or media address dataAll address data contained on pages 0, 1, and 2 relateto program timing and should be processed accord-ingly. Two types of address dialects can be stored inthese pages: auxiliary time address and mediaaddress.Auxiliary ti
13、me address data can be stored at directoryindex lines 0 through 9 of pages 0 and 1, and lines 0through 3 of page 2, which correspond to auxiliarytime address hours 00 through 23. This dialect, asspecified in SMPTE RP 169, provides a second timeaddress with the same order and format as theprimary tim
14、e address data.Media address data other than time address can bestored in directory index lines 10 through 15 of pages0 and 1 and lines 4 through 15 of page 2. 3.2.2 Control dataOne page (page 15) containing 16 lines is assignedto control data which consists of instructions requiringreal-time comman
15、d and execution. A frame carryingcontrol data shall include an 8-bit checksum and havehighest priority for encoding (see 3.4.5).3.2.3 Applications dataTwelve pages, for a total of 192 lines, are reservedfor user application subsets. A particular applicationdialect may specify a group of page-line su
16、bsets.3.3 Use of binary groups3.3.1 Binary group flag bitsWhen the data structure conforms to this format, thebinary group flag bits shall be set in accordance withANSI/SMPTE 12M for page-line applications.Figure 2 - Page-line directory24- and 30-fps systems 25-fps systemsBinary group flag Bit value
17、 LTC bit VITC bit LTC bit VITC bitBGF2 1 59 75 43 55BGF1 0 58 74 58 74BGF0 1 43 55 27 35Table 1 - Binary group flag values for page-line encodingANSI/SMPTE 262M-1995Page 3 of 5 pages3.3.2 Subset applicationsEach frame of time and control code may contain onlyone type of data, identified by the value
18、 of the directoryindex. The choice of data types and their repetitionfrequency is left to the discretion of the user.3.3.3 Error detectionError detection may be provided for as an 8-bit check-sum. This consists of the twos complement of the leastsignificant byte (modulo 256) of the sum of the speci-
19、fied binary bytes.3.4 Message formats3.4.1 Control codes (see figure 3)This format consists of 2-byte instructions conveyingreal-time commands in binary bytes 2 and 3. Binarybyte 1 carries an 8-bit checksum of binary bytes 2, 3,and 4.3.4.2 Single-frame messages (see figure 3)This format consists of
20、a 3-byte message transmittedwithin binary bytes 1, 2, and 3. Certain applicationsdialects may specify binary byte 1 as an 8-bit check-sum of binary bytes 2, 3, and 4.3.4.3 Message strings (see figure 4)A string of formatted data can be encoded as amessage string comprising three types of frames:pref
21、ix frame(s), message frame(s), and suffixframe(s), each of which is assigned a unique directoryindex. The maximum message length shall beconstrained to 256 frames.The prefix and suffix frames shall be structured asfollows: Binary byte 1 carries an 8-bit checksum ofbinary bytes 2, 3, and 4. Binary by
22、tes 2 and 3 providemessage specifier information, such as message ID,destination address, and message length. Multipleprefix and suffix frames may be specified for a mes-sage string, as required by the application dialect.Each prefix and suffix frame shall be identified as suchby a unique directory
23、index allocation.The message frame shall be structured as follows:Each message frame carries message data in binarybytes 1, 2, and 3, while binary byte 4 carries thedirectory index, indicating a message frame.When transmitting a message conforming to ISO/IEC646 and ISO/IEC 2022, unused bytes of the
24、messageframe preceding the first suffix frame shall be nullfilled. Use of the parity bit provided with this data typeallows error detection on the message data.Figure 3 - Control code and single-frame message formatsANSI/SMPTE 262M-1995Page 4 of 5 pages3.4.4 Extended message strings (see figure 4)A
25、string of unformatted data conforming to ISO/IEC646 and ISO/IEC 2022 can be combined with themessage prefix and suffix frames, as defined in 3.4.3,to provide an extended message string format. Thedata type carried in the extended message frames issignalled by the binary group flag bits, in accordanc
26、ewith ANSI/SMPTE 12M.3.4.5 Message encoding priorityIn the absence of other applications guidelines, andin the event that multiple sources of directory indexdata request encoding to the binary groups ofthe same time address location, the higher pagenumbered directory index application shall takeprio
27、rity. Similarly, priority shall be given to higher linenumbered applications for time-coincident directoryindex data of the same page number. Applicationsdialects should specify source priority coding forsituations where time-coincident data of the samepage and line number may occur.Figure 4 - Message and extended message formatsANSI/SMPTE 262M-1995Page 5 of 5 pages
