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1、BRITISH STANDARD BS 6865:1987 IEC 461:1986 Incorporating Amendment No. 1 Specification for Time and control codes for video tape recorders (Implementation of CENELEC HD 507 S1) UDC 621.397.452-5:003.29 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy,
2、 (c) BSI BS 6865:1987 This British Standard, having been prepared under the direction of the Electronic Equipment Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 June 1987 BSI 01-2000 The following BSI references relate to the work on this stand
3、ard: Committee reference EEL/22 Draft for comment 86/28131 DC ISBN 0 580 16009 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Electronic Equipment Standards Committee (EEL/-) to Technical Committee EEL/22, upon which the following bod
4、ies were represented: Association of Sound and Communications Engineers Limited British Broadcasting Corporation British Kinematograph, Sound and Television Society Council for Educational Technology for the United Kingdom Electronic Engineering Association Independent Television Companies Associati
5、on Training and Educational Systems Testing Bureau Amendments issued since publication Amd. No.Date of issueComments 6418August 1990Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865:1987 BSI 01-200
6、0i Contents Page Committees responsibleInside front cover National forewordii Chapter I. Longitudinal time code (LTC) 1Scope1 2Modulation method1 3Code format1 4Structure of the time address5 5Additional colour television requirements6 6Waveform of the time and control code signal9 7Timing of the st
7、art of the code word11 Chapter II. Vertical-interval time code (VITC) 1Scope12 2Modulation method and bit-rate12 3Code format 625/50 systems15 4Code format 525/60 systems16 5Structure of the coded data17 6Relationship between the vertical-interval time code and the television signals prior to record
8、ing20 7Specifications of the characteristics of the VITC signal prior to recording21 Appendix A The use of cyclic redundancy check codes for error detection23 Appendix B Definition of field one in the eight-field sequence of the PAL signal24 Appendix C Timing relationship between the subcarrier refe
9、rence and the line synchronizing pulses for PAL recordings24 Figure 1 Modulation system “Bi-Phase Mark”1 Figure 2a Constitution of the code word (longitudinal code)2 Figure 2b Constitution of the code word (longitudinal code)3 Figure 3 Use of binary groups of the time-and-control code to describe th
10、e ISO character coded with 7 or 8 bits4 Figure 4a Waveform of the time and control code signal (625/50)9 Figure 4b Waveform of the time and control code signal (525/60)10 Figure 5a Start of the code word in the field-blanking interval (625/50)11 Figure 5b Start of the code word in the field-blanking
11、 interval (525/60)11 Figure 6 Modulation system “non-return to zero”12 Figure 7a Relationship between vertical-interval time code and longitudinal time code for 625/50 system13 Figure 7b Relationship between vertical-interval time code and longitudinal time code for 525/60 system14 Figure 8 Use of b
12、inary groups of the time-and-control code to describe the ISO characters coded with 7 or 8 bits18 Figure 9a Position of the code word on the line (625/50)20 Figure 9b Position of the code word on the line (525/60)20 Figure 10a Waveform of the code signal (625/50)21 Figure 10b Waveform of the code si
13、gnal (525/60)22 Figure C.1 Vectorial representation of the chrominance signals25 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865:1987 ii BSI 01-2000 National foreword This British Standard ha
14、s been prepared under the direction of the Electronic Equipment Standards Committee and is identical with Publication 461:1986 “Time and control code for video tape recorders;”, published by the International Electrotechnical Commission (IEC). This British Standard is also in agreement with Harmoniz
15、ation Document HD 507 S1 published by the European Committee for Electrotechnical Standardization (CENELEC). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain convent
16、ions are not identical with those used in British Standards. The Technical Committee has reviewed the provisions of ISO 2022 and CCIR Report 624-2, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A British Standard identical
17、 with ISO 2022 is in preparation. Copies of CCIR documents can be obtained from: International Telecommunications Union Places des Nations CH 1211 Geneva 20 Switzerland. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsi
18、ble for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International StandardCorresponding British Standard ISO 646:1983BS 4730:1985 Specification for UK 7-bit coded character set (Identical exercising nationa
19、l options) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 26, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table
20、on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865:1987 BSI 01-20001 Chapter I. Longitudinal time code (LTC) 1 Scope This chapter specifies a digital code format and modulation method to be used for timing and
21、 control purposes of television-tape machines and/or associated separate audio recorders. The encoded signal shall be recorded on the cue track or on an auxiliary longitudinal track. 2 Modulation method The modulation method shall be such that a transition occurs at the beginning of every bit period
22、. In the case of a “zero” there is no second transition within the bit period. In the case of a “one” there is a second transition, a half-bit period after the start of the bit. This method is also known as “Bi-Phase Mark” (see Figure 1). 3 Code format 3.1 A unique code word shall be associated with
23、 each television frame. 3.2 Each code word shall consist of 80 bits numbered from 0 to 79, inclusive. 3.3 The bits shall be assigned as shown in Figure 2a (625/50), page 2 and Figure 2b (525/60) and as described hereinafter: Figure 1 Modulation system “Bi-Phase Mark” 625/50525/60 03Units of framesUn
24、its of frames 47First binary groupFirst binary group 89Tens of framesTens of frames 10Unassigned address bitDrop frame flag bit 11Colour-lock flag bitColour-lock flag bit 1215Binary group No. 2Binary group No. 2 1619Units of secondsUnits of seconds 2023Binary group No. 3Binary group No. 3 2426Tens o
25、f secondsTens of seconds 27Binary group flag bitBi-phase mark phase-correction bit 2831Binary group No. 4Binary group No. 4 3235Units of minutesUnits of minutes 3639Binary group No. 5Binary group No. 5 4042Tens of minutesTens of minutes 43Binary group flag bitBinary group flag bit 4447Binary group N
26、o. 6Binary group No. 6 4851Units of hoursUnits of hours 5255Binary group No. 7Binary group No. 7 58Unassigned bitUnassigned bit 59Bi-phase mark phase correction bitBinary group flag bit Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865
27、:1987 2 BSI 01-2000 3.3.1 625/50 systems 6063Binary group No. 8Binary group No. 8 6479Synchronizing wordSynchronizing word 6465Fixed zeroFixed zero 6677Fixed oneFixed one 78Fixed zeroFixed zero 79Fixed oneFixed one Figure 2a Constitution of the code word (longitudinal code) Licensed Copy: sheffieldu
28、n sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865:1987 BSI 01-20003 3.3.2 525/60 systems 3.4 Boundaries of the code word The code word shall start at the clock edge before the first bit (bit zero). The bits shall be evenly spaced in such a way that the code wo
29、rd period shall coincide with the period of one television frame. The bit rate shall be 80 times the frame rate (per second) of the television system used. Figure 2b Constitution of the code word (longitudinal code) Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Unco
30、ntrolled Copy, (c) BSI BS 6865:1987 4 BSI 01-2000 3.5 Use of binary groups 625/50 (525/60) The binary groups are intended for the storage of supplementary data by the users. The 32 bits within the eight binary groups may be assigned in any way without restrictions if the character set used for the d
31、ata insertion is not specified and the binary group flag bits Nos. 27 and 43 both are zero (525/60 systems: bit positions 43 and 59). If an eight-bit character set conforming to ISO Standard 6461) and ISO Standard 20222) is signalled by the binary group flag bits Nos. 27 and 43 (525/60 systems: bit
32、positions 43 and 59) the characters should be inserted in accordance with Figure 3, page 4. The information carried by the user bits is not subjected to any regulation. At present, the following truth-table applies: The unassigned states of the truth-table cannot be used and their assignment is rese
33、rved for the IEC. If it becomes clear that no use is to be expected for them, it is possible that bit No. 43 (59) can again become unassigned and thus available for other applications, while still retaining bit No. 27 (43) to signal the presence of eight-bit ISO characters. It should be noted that,
34、in each time code word, some user bits will be decoded before bits Nos. 27 (43) and 43 (59) are encountered. The data in these earlier user-bit locations must not be lost. If the time code is locked to the four-field sequence in NTSC or the eight-field sequence in PAL, as defined in Sub-clause 5.2,
35、bit No. 11 shall be set to “1”. 3.6 Assigned and unassigned bits 3.6.1 625/50 systems Colour-lock flag bit The colour-lock flag bit No. 11 shall be set to “1” when the time code is locked to the associated PAL colour signal in accordance with the eight-field sequence, and when the video signal has t
36、he “preferred subcarrier-to-line-sync, phase”. Bi-phase mark phase-correction bit. The purpose of the phase-correction bit is to compensate for phase reversals in the bi-phase mark modulation that could occur when code inserts are performed. Such compensation may be required when code inserts modify
37、 the content of any of bits Nos. 0 to 63, bit No. 59 excluded. 1) ISO Standard 646: Information Processing ISO 7-Bit Coded Character Set for Information Interchange. 2) ISO Standard 2022: Information Processing ISO 7-Bit and 8-Bit Coded Character Sets Code Extension Techniques. Bit No. 27 (43) Bit N
38、o. 43 (59) Character set not specified00 Eight-bit character set conforming to ISO Standards 646 and 202210 Unassigned01 Unassigned11 Figure 3 Use of binary groups of the time-and-control code to describe the ISO character coded with 7 or 8 bits Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05
39、 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865:1987 BSI 01-20005 In order that the magnetization transient between bit-cell 79 of one word and bit-cell 0 of the next shall always be in the same direction, bit No. 59 will be put in a state where every 80-bit word will contain an even nu
40、mber of logic zeros. This requirement results in the following truth-table for bit No. 59: In drawing up this specification, the use of time code write/read systems that have equal polarity relations between input/output voltage and the tape magnetization is assumed. This specification should not be
41、 understood as a requirement for time code insert capacity in television tape-machines in situations where tapes have to be interchanged, until further notice from the IEC. Unassigned bits Bits Nos. 10 and 58 are reserved for future assignment and shall be zeros until specified by the IEC. 3.6.2 525
42、/60 systems Six bits are reserved within the address group, 4 for identifying operational modes, 1 for bi-phase correction, and 1 unassigned, but reserved for future assignment and defined as zero until further specified by the IEC: 4 Structure of the time address 4.1 The basic structure of the time
43、 address is based upon the Binary Coded Decimal (BCD) system. In those cases when the count does not rise to 9, only two or three bits are required, rather than four bits as is normal in the BCD code. 4.2 Assignment of the time bits Number of logic zeros in bits Nos. 0 to 63 (59 excluded) Bit 59 Odd
44、1 Even0 Bit No. 10 Drop Frame Flag. If certain numbers are being dropped to resolve the difference between real time and colour time, as defined in Sub-clause 5.1, a “1” shall be recorded. Bit No. 11 Colour Frame Flag. If colour frame identification has been intentionally applied, as defined in Sub-
45、clause 5.2, a “1” shall be recorded. Bit No. 27 “Bi-phase Mark” Phase Correction. Shall be put in a state so that every 80-bit word will contain an even number of logic zeros. This requirement results in the following table for bit 27: Number of logic zeros in bits Nos 0 to 63 (27 excluded) Bit No.
46、27 Odd1 Even0 Bits Nos. 43 and 59 Binary Group Flag Bits. These 2 bits shall be set in accordance with the truth-table as specified in Sub-clause 3.5. Bit No. 58 Unassigned Address Bit. “0” until assigned by the IEC. Frames UnitsBits 03: four bits BCD arranged 1, 2, 4, 8 count 0 to 9. TensBits 89: t
47、wo bits BCD arranged 1, 2 count 0 to 2. Seconds UnitsBits 1619: four bits BCD arranged 1, 2, 4, 8 count 0 to 9. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 09:50:09 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6865:1987 6 BSI 01-2000 5 Additional colour television requirements 5.1 System
48、 M colour television requirements Because the vertical frame rate of a System M colour signal is 29.97 frames/second, counting of frames will yield approximately a 4-second timing error in one hour. Therefore, two modes of operation are allowed: 5.1.1 Mode “1” 5.1.1.1 M/NTSC System To resolve the co
49、lour time error, the first two frame numbers (0 and 1) at the start of each minute shall be omitted from the count except for minutes 0, 10, 20, 30, 40 and 50. When this mode is used, bit No. 10 shall be “1”. 5.1.1.2 M/PAL System To resolve the colour time error, the first four frame numbers (1 to 4) at the start of every second minute (even minute numbers) shall be omitted from the count except for minutes 0, 20 and 40. When this mode is used, bit No. 10 shall be a “1”. 5.1.2 Mode “0” For every