1、 Rec. ITU-R BR.469-7 1 RECOMMENDATION ITU-R BR.469-7*, *Analogue composite television tape recording Standards for the international exchange of television programmes on magnetic tape*(Question 239/11) (1970-1974-1978-1982-1986-1990-1992-2002) The ITU Radiocommunication Assembly, recommends that mag
2、netic recordings of analogue composite signals used for the international exchange of television programmes should meet the following standards: 1 Television standards Recording on magnetic tape of television programmes for international exchange should be carried out in accordance with one of the f
3、ollowing classes of television systems: 625-lines, 50 fields/s; 525-lines, 60 fields/s. NOTE 1 The characteristics of the television systems are given in Recommendation ITU-R BT.470. _ *Radiocommunication Study Group 6 made editorial amendments to this Recommendation in 2001 in accordance with Resol
4、ution ITU-R 44. *This Recommendation should be brought to the attention of the International Electrotechnical Commission (IEC). *International programme exchange is defined as the transmission of television or sound programme material (or components thereof) among professional parties in different c
5、ountries. It should be based on internationally agreed and widely employed technical standards or operating practices, except by prior bilateral agreement among the parties involved. 2 Rec. ITU-R BR.469-7 2 Recording format 2.1 Analogue recording of composite video signals The recordings should conf
6、orm with the following format: 25.4 mm helical recording Type C: IEC Publication 558 (1982 and Amendment No. 1 (1987). NOTE 1 Tighter mechanical tolerances for the audio tracks have been agreed between the EBU and SMPTE (see EBU Recommendation N6-1989). NOTE 2 In the EBU, for 625-line 50 field/s rec
7、ordings, no essential components of an exchange programme tape shall be recorded in the area between audio track 3 and the control track, unless prior agreement has been obtained. NOTE 3 Guidelines for the storage of magnetic tapes are contained in EBU Tech. 3202. Prior agreement is necessary betwee
8、n the concerned parties regarding this format when it is used for programme exchange. 3 Specifications for programme sound recording 3.1 General The sound reference level shall correspond to a recorded short circuit flux of 100 5 nWb/m of track width (r.m.s.) (Federal Republic of Germany: 90 5 nWb/m
9、), at 1 000 Hz. (In some countries, a 400 Hz reference tone is used.) Normal operational practice will result in programme peaks corresponding to a maximum short circuit flux between 250 and 310 nWb/m (r.m.s.), i.e. about 9 dB above reference level. These maximum recorded levels correspond to the su
10、bjective overload level for television tape materials currently used for the international exchange of programmes. NOTE 1 When the programme peaks are measured by means of a programme meter, due account should be taken of the integration time of the instrument. 3.2 Recording characteristic Type C re
11、cording The recording characteristic is defined in the relevant IEC Publication. 3.3 Programme sound allocation Type C recording Table 1 presents in tabular form the preferred allocation of tracks to audio channels for the case when two synchronous sound channels accompany a picture. NOTE 1 More det
12、ailed information (including other tape formats) is contained in EBU Recommen-dation R38-1987. Rec. ITU-R BR.469-7 3 NOTE 2 Although many broadcasting organizations use companding for internal purposes (details of the techniques used by EBU members are given in EBU Recommendation R39-1986), the use
13、of audio companding on recordings intended for international exchange is not recommended. TABLE 1 4 Editing Electronic editing shall maintain an off-tape synchronizing pulse train with a phase relationship to the playback reference of the machine sufficiently closely to avoid visible disturbance; th
14、e requirement for dominant field editing is given in Annex 1; for Type C recorders, the preferred operating practice for editing recordings made in PAL as well as the use of the PAL eight-field information on the control track is described in Annexes 2 and 3. NOTE 1 The EBU has issued Technical Stat
15、ement D23-1984 describing in detail the EBU requirements for synchronizing pulse generators for 625-line/50 fields PAL signals. The output signal timing stability of PAL broadcast video tape machines is suggested to be within: 2.5 ns quasi peak-to-peak for random perturbations; 0.4 ns peak-to-peak f
16、or periodic perturbations for a single record/replay cycle; Information on the time and control code required for editing can be found in Recommen-dation ITU-R BR.780 and IEC Publication 461. Format Operation mode Channel C(1), (2)Exchange of finished monophonic programmes Monophonic programme mix T
17、rack 1 International sound (if any) Track 2 Exchange of finished stereophonic television programmes Stereo left Track 1 Stereo right Track 2 Exchange of original news recording Commentary (if any) Track 1 International sound Track 2 (1)Track 1 is the inner track in format C. (2)Audio track 3 in form
18、at C is allocated to the time code and may not carry an audio channel except by mutual agreement. Audio track 4 is optional and, in the case of an exchange of stereo recordings, it may be used by the sending organization, by mutual agreement, to record the monophonic mix; in the case of an exchange
19、of monophonic programmes, it may be used by the receiving organization to record its own dubbed sound. 4 Rec. ITU-R BR.469-7 5 Composition and duration of leaders and trailers Leader and trailer sections of monophonic recordings should be located on the tape in conformity with the sequence shown in
20、Table 2. For stereophonic Type C recordings, see Table 3. TABLE 2 Leader and trailer sections for the exchange of recorded television programmes with monophonic sound Tape section Duration (s) Picture Sound (on any channel carrying programme sound) Control track signal Protection leader 10 (minimum)
21、 Blank tape Alignment leader 60 (minimum) Alignment signal 1 000 Hz at reference level(1)Uninterrupted Optional 5 (maximum) Blank tape Identification leader 15 (minimum) Programme identification Spoken identification preferred, or silence 8 Black or cue(2)Silence or cue Uninterrupted Leader Cue-up l
22、eader 2 Black(2)Silence Programme(3)Playing time of programme Programme Run-out trailer 30 (minimum) Black(2)Silence (1)See 3.1. (2)In the case of colour recordings the black signal should be colour black. It is desirable that the colour field sequence (8 fields in PAL, 4 fields in NTSC) should cont
23、inue uninterrupted in relation to the beginning and end of the programme recording. (3)Where the time and control code is recorded on the assigned longitudinal track, the time indication of the programme start should be shown on the label accompanying the tape (see 8.3). Rec. ITU-R BR.469-7 5 TABLE
24、3 Leader and trailer sections for the exchange of recorded television programmes with stereophonic sound on format C tape Tape section Duration (s) Picture Sound track 1 Sound track 2 Control track signal Protection leader 10 (minimum) Blank tape Alignment leader 60 (minimum) Alignment signal(1)1 00
25、0 Hz at reference level(2), interrupted(3), (4)1 000 Hz at reference level(2), (4)UninterruptedOptional 5 (maximum) Blank tape Identification leader 15 (minimum) Programme identification Spoken identification preferred, or silence Spoken identification preferred, or silence Leader 8 Black or cue(5)S
26、ilence or cue Silence or cue Cue-up leader 2 Black(5)Silence Silence UninterruptedProgramme(6)Playing time of programme Programme Run-out trailer 30 (minimum) Black(5)Silence Silence Uninterrupted(1)Examples of suitable alignment signals for 625 lines, 50 field/s systems will be given in a draft new
27、 Recommendation. (2)See 3.1. The tones for both tracks must be coherent (i.e. from the same source) and in phase. (3)The tone should be interrupted for 0.25 s every 3 s to enable identification of stereophonic recordings. The interruption may be made without using automatic equipment by organization
28、s that only very occasionally need to interchange stereophonic video tape recordings. Under these circumstances, it is recognized that the specified interruption duration will not be strictly adhered to. (4)In Australia the reference tone is on track 1 and the interrupted reference tone is on track
29、2. This is done to identify tracks and retain compatibility with mono track 1 reference tone. (5)In the case of colour recordings, the black signal should be colour black. It is desirable that the colour field sequence (8 fields in PAL, 4 fields in SECAM) should continue uninterrupted in relation to
30、 the beginning and end of the programme recording. (6)Where the time and control code is recorded on the assigned longitudinal track, the time indication of the programme start should be shown on the label accompanying the tape. 6 Rec. ITU-R BR.469-7 6 Winding of the tape on the spools 6.1 The tape
31、should be wound on the spools specified in IEC Publications 347 and 503, with the start of the recording on the outside. In the case of Type C recordings the magnetic surface should be towards the hub of the spool. 6.2 The tape must be wound in such a way as to minimize the possibility of damage dur
32、ing transport; e.g. by using a constant winding tension. To prevent unwinding, the head end of the tape should be secured during storage and transport, by a suitable mechanical means, e.g. Scotch 8125 tape or equivalent; the use of a tape collar during transport is recommended. 6.3 Recordings of a s
33、ingle programme of up to 90 min duration should preferably be on one spool. 6.4 Separate programmes should always be on separate spools. 7 Packaging Programme spools should be packed in containers affording protection against mechanical and environmental damage. The materials of which containers are
34、 constructed should not emit toxic fumes in the event of exposure to fire. 8 Programme identification 8.1 At least the following information should be supplied with each recorded television tape: name of the organization which made the recording; title of programme, or title, sub-title and episode n
35、umber; total number of spools, and number of the spool in the sequence when the programme is contained on more than one spool; reference number (library number) of programme or of tape; total playing-time, and playing-time of the programme material recorded on the tape; in the case of 25.4 mm (one-i
36、nch) recording: the format, i.e. Type C; line and field system (625/50 or 525/60); indication of the colour system, for colour recordings; which audio tracks have been used; the content of each audio track; indication of monophonic or stereophonic recording; whether the sync track is recorded. 8.2 T
37、he information required in 8.1 shall be provided in at least one of the official languages of the ITU. 8.3 The information required in 8.1 shall be provided on labels affixed both to the programme spool and its container. Rec. ITU-R BR.469-7 7 ANNEX 1 Recommended dominant field for 625-line 50 Hz vi
38、deo processing The dominant field is that field of the video waveform at which a change of picture material occurs. Historically, and for technical reasons, the beginning of field 2 was used in early video tape recorders as the edit point. This could cause edit point decision difficulties if the vid
39、eo signal contained picture material that changed at field 1. This would arise, for instance, if a telecine machine started its scanning of each new film frame at the beginning of field 1. Modern video tape recorders usually edit at the beginning of field 1. Like other video processing equipment, fo
40、r example electronic graphics equipment, the selection of other modes is possible. Where picture material is switched, processed and edited in a complex way, a lack of discipline in the choice of dominant field can lead to difficulties and confusion. To avoid these, it is recommended that field 1 sh
41、ould be dominant in all but exceptional cases. Where manufactured equipment permits selection of the field dominance, this should require positive user action and be clearly indicated when a non-standard condition exists. Equipment should be set by users to operate in the field 1 dominant mode unles
42、s particular special requirements dictate otherwise. ANNEX 2 Use of the PAL eight-field information on the control track of Type C recordings Playback modes Four-field lock mode The machine should lock to a PAL four-field sequence. A PAL four-field sequence can be derived from the eight-field edit p
43、ulse. Eight-field frame mode The machine should use an eight-field edit pulse to secure eight-field framing but only during the initial lock-up period. These two modes shall be switch-selectable. 8 Rec. ITU-R BR.469-7 ANNEX 3 Picture shift following a video tape recorder (VTR) edit in PAL systems Un
44、desirable horizontal picture shift following a VTR edit point may occur under certain conditions. When the picture content is similar before and after the electronic splice point, the shift may be easily visible and annoying; such picture jumps are especially irritating in the case of electronic ani
45、mation. These horizontal picture shifts are the result of time-base-corrector action, which may be due to the PAL 8-field structure (a similar problem is experienced in 525-lines, 60 fields/s systems, with the NTSC four-field sequence) or to changes in the phase relationship between sub-carrier burs
46、t and line-synchronizing pulse caused by equipment instability or adjustment, or by a change to a source with a different burst-to-sync phase relationship. Recommendation ITU-R BT.470 defines the relationship between sub-carrier phase and line synchronizing pulse. However, for sophisticated editing,
47、 it is mandatory that the video signals to be edited are recorded with a phase (EU) = 0, and with a deviation not greater than 20 for the extrapolated EU-component of the video burst (see Note 1) at the leading edge of the line-synchronizing pulse of line 1 of field No. 1 (numbering of fields accord
48、ing to Recommen-dation ITU-R BT.470, Table 2, 2.16). The central value of = 0 is called “the preferred sub-carrier-to-line synchronizing (Sc-H) phase for video signals recorded on tape”. In addition, jitter and drift of sub-carrier phase with respect to line synchronizing should be less than 1.5 ns
49、( 2.5) for synchronizing pulse generators (SPGs) providing the reference for editing suites. These SPGs must supply a “field No. 1” indication for the correct, field-coincident operation of associated PAL-coders, time-code generators and recorders. A visual display of the frame number of a selected edit point within the 8-field sequence derived from the time and control code is useful to the programme producer making the edit decisions in order to enable him to achieve, w
