ITU-R BR 1215-1995 Handling and Storage of Television and Sound Recordings on Magnetic Tape《磁带上电视和声音记录的处理和储存》.pdf

1、Rec. ITU-R BR.1215 1SECTION 10/11R-B: TELEVISION RECORDINGRECOMMENDATION ITU-R BR.1215*HANDLING AND STORAGE OF TELEVISION AND SOUNDRECORDINGS ON MAGNETIC TAPE(Question ITU-R 102/11)(1995)Rec. ITU-R BR.1215The ITU Radiocommunication Assembly,consideringa) that international exchange of television and

2、 sound programmes is based to a large degree on magnetic tape;b) that such programmes are archived for a considerable period of time;c) that during archival storage such tapes may be used many times;d) that loss of technical quality during the lifetime of the archived programme must be avoided;e) th

3、at proper care when handling the tape before, during and after each archival interval is a prerequisite for thesuccessful retrieval of the programme; the increased storage density on tape of modern digital recording formats mayrequire special attention in this respect,recommends1 that the handling a

4、nd archival storage of programmes on tape should be carried out following the guidelinesgiven in Annex 1.NOTE 1 A glossary of different tape damages can be found in Annex 2.ANNEX 1Handling and storage of magnetic tape1 Handling of magnetic tape Only high quality tapes should be used, preferably thos

5、e with a proven good long-term performance. Cleanliness is extremely important in the recording area. Smoking, eating and drinking should not be permitted.Adequate filtering should be applied to the incoming air to reduce the size of the dust particles. Regular cleaning ofthe tape drive is necessary

6、. Tapes must be kept away from magnetic fields; tapes should not be stacked on top of equipment. The straymagnetic field at any point on the tape surface should not exceed a field strength of 4 000 A/m. Open reel or cassette tapes should never be exposed to the sun. Tapes should be fully wound or re

7、wound before removal from a transport and returned to their containers whenthey are not in use._*This Recommendation should be brought to the attention of the Telecommunication Development Sector (ITU-D).2 Rec. ITU-R BR.1215 Tapes should not be subjected to rapid temperature changes. The maximum tem

8、perature and humidity gradient thatthe tape is subjected to should not exceed 10 C/h and 10% of RH/h. Regular electrical and mechanical alignment of the tape recorder should be carried out. Careful cleaning anddegaussing of the complete tape transport, including the guides, the capstan, the scanner,

9、 the heads, etc., arenecessary. For this cleaning, a spray cleaner can be used, for example “trichloroethane”. Excessively low tape tension which results in loose winding must be avoided as this will lead to permanent tapedamage after storage. To avoid the risk of head clogs, the relative humidity d

10、uring recording and replay of the tape should be kept withinthe limits given in 2. A tape being brought in from an environment which differs from that of the storage area must be acclimatized fullyand completely rewound, before it is put into the long-term storage. If storage and operating area temp

11、eraturesdiffer by more than 8 C, allow an acclimatization time of 4 h for every 10 C. In case of extreme outdoor climaticconditions, it would be advisable to carry tapes in isothermal containers which should be closed before leaving thestorage area, and reopened only after arrival in the operating a

12、rea.In winter-time, major temperature fluctuations may be unavoidable, which might lead to condensation. Anacclimatization period of up to 24 h must therefore be allowed.2 Long-term archival storage of magnetic tape (see Note 1) Cleanliness is absolutely necessary. The incoming air must be filtered

13、and should develop a positive pressure in thestorage area. Smoking, eating or drinking should not be permitted. Temperature and humidity should be kept as stable as possible, and preferably below those in the operatingenvironment. Suitable values for a storage period up to ten years are in the range

14、: temperature: 18-24 C humidity: 35-45% RHFor a storage time beyond 10 years the following values are recommended: temperature: +17 C humidity: 30%Variations from selected storage temperature and humidity should be kept within 2 C and 5% RH throughout theentire storage period. Each tape open reel an

15、d cassette should be kept in its container. The container should be designed to giveadequate protection against debris, sprinklers, fire and careless handling. The tapes should be stored in an uprightposition, preferably with the spools suspended by the hubs. If the tape is kept in a sealed bag insi

16、de the container, itis important that the atmosphere in the bag is dry. When the tapes are to be stored in plastic bags, these should be sealed in a dry environment, the tapes themselveshaving been stored in the same environment for some hours. When no special equipment is available, such as avacuum

17、 bag sealing machine, it would be preferable to store the tapes with no bag at all, but in their normalcontainer. Except for labels, paper should not be stored inside a storage container. Shelves should allow for adequate air flow to ensure that the conditioned environment is maintained throughout t

18、hestorage area. Magnetic latches on tape storage cabinets should not be used, since they could cause partial erasure of tapes ifbrought closer than 7 cm to the magnetic latch. Every tape in an archive should be physically inspected at least every three to five years for playback performance,debris,

19、contaminants, container gasket deterioration etc. A full length wind/rewind should be completed on eachtape at least once in every ten years. It is recommended to keep the storage area free from any magnetic fields of noticeable strength, i.e. greaterthan 1 kA/m.Rec. ITU-R BR.1215 3 The storage area

20、 must have an adequate fire protection system of a type using CO2or some other non-aggressivechemicals. A tape being brought in from an environment which differs from that of the storage area must be acclimatized fullyand completely rewound, before it is put into the long-term storage. All the tapes

21、 in storage should be wound from one end to the other at regular intervals, preferably every two tothree years, with a maximum of five years. This procedure should possibly be carried out on a tapeevaluator/cleaner to give a smooth wind at a correct tape tension and to remove debris from the magneti

22、c coating(e.g. the white powder developed by certain old tapes). Regular inspections should be made of the tapes in order to control the real condition of the recorded material. Thecheck could be performed on samples of the actual programme tapes or on specially prerecorded test tapes,representative

23、 of the different batches in the archives. The tapes in question shall be replayed and visuallyexamined. Careful maintenance of the machine replaying the archived programme is extremely important. In order to keepmachines of earlier formats in continuing operation, skilled operators will be required

24、. These operators will need tobe specially trained to operate and maintain these machines, as well as to carry out mechanical splicing of tapes asthis is sometimes the only way to recover a damaged programme.NOTE 1 Although accelerated lifetime tests carried out by a number of tape manufacturers sug

25、gest a lifetime ofmodern tapes well beyond 10 to 15 years, long-term storage may affect the properties of certain tapes, mainly due tomechanical and/or chemical effects. Consequently, there is no way to guarantee a particular tape will give perfect soundand vision recovery, after several years of st

26、orage. The only way to verify the condition of the programme material inarchives is by regularly taking out actual samples of the tapes for inspection, and playing them back.ANNEX 2Glossary of tape defectsAccordioning (corrugated surface, pleating, wash-board)A form of cinching where the tape surfac

27、e has several folds close together.BandsStresses in the tape that are parallel to the edge will cause evenly spaced bands across the tape.BlockingThe adhesion of oxide of one layer to the back of the adjacent layer. May result in oxide shedding. Caused by a tighttape pack subjected to a hot, humid e

28、nvironment for a long time.Buckled pack (wavy pack)Deformation of the circular form of the tape pack. The pack periphery feels lumpy. Can be caused by an edge-curledtape wound too loose.CinchingFold-over of tape within the pack. This may result in cracked oxide and permanent tape damage. Caused by a

29、 loose packbeing wound with fast acceleration and then stopped.4 Rec. ITU-R BR.1215Country-laning (skew)Variation in straightness of the edges of the tape with respect to a theoretical tape centre line. Independent of tape widthvariation.Edge curl (lipping)Stretched tape edge causing the diameter of

30、 the tape pack near the edge being larger than at the centre.Leafing (pop-stranding, scattered wind, stepping)Individual turns standing out from the tape pack. Can be caused by imperfect alignment of the tape guides, particularlywhen the tape is stopped and restarted during spooling. May lead to edg

31、e damage affecting the outer tracks, i.e. audio,time code and control signals.Loose packThe outer portion of the tape pack can be easily rotated by hand due to very loose winding and/or very severetemperature cycling in storage or during transport. In extreme cases, voids can be observed in the pack

32、, calledwindowing.Particle shreddingThe magnetic layer flakes off from the tape base due to change in the characteristics of the binder. This may lead tohead-clogging and will cause drop-outs or even complete loss of information.PowderingDeposition on the tape surface of components from the binder d

33、ue to chemical instability of the formulation. This willcause severe head-clogging on the machine.Print-throughMagnetic flux from one tape layer will make a weak “recording” on adjacent layers under the influence of time,temperature and external fields. The effect is wavelength dependent and will no

34、t affect the vision, only the sound isaffected as pre- and post-echoes. Modern tapes with high coercivity are less inclined to develop print-through.ScratchesPhysical damage to the magnetic coating. May be caused by misaligned or dirty transport components, or improperhandling and storage.SpokingThe

35、 non-circular winding due to splices, dirt, etc. within the layers, giving the appearance of spokes.Width variationIndependent variation of each edge of the tape with respect to a theoretical centre line. Independent of tape skew.WindowingVoids in the tape pack due to an extremely loose pack.Static charges could be kept to a minimum by selecting appropriate materials for the floor and the walls. If necessary, a“static drain” can be fitted to the carpeting._