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No.20- Spring1985 The Quarterly for BBC Engineering Staff Please Circulate

BBC 1 - Bright New World

Recently many viewers will have Descrip tion by a spotlight above tlte viewer. noticed a new look to BBC 1. For The symbol generated by the many years the channel logo has equipment is a rotating image of Design been the familiar 'rotating world', the world with a caption displayed Graphic Design at Television generated from a mechanical beneath. The image is larger than Centre undertook the artistic model. Originally this was pro- its predecessor, and there is no design of the symbol. Clearly this duced by a remotely controlled reflecting mirror, but the detail had to be done in very close con- camera, affectionately known as and accuracy are much greater. junction with the engineers in Nod dy, which was also used for the old mechanical clock and fault captions. Most of Noddy's functions have been replaced by electronic generators, but the World was still being produced by a caption scanner, followed by a colour synthesiser and PAL coder. This required regular maintenance, and alignment of the video pro- cessing to produce consistent resul ts. On February 18th a new Symbol was introduced. The generating equipment is all electronic, using the latest digital techniq ues. Some digitally generated pictures suffer from an effect known as 'aliassing'; this is most noticable on sloping lines and circles as small steps, which show the graphic being made up of discrete lines. The new equipment is fully 'anti-aliassed' on both the logo and the captions, which sub- stantially improves the overall The caption is customised for each Designs Department. Over the last quality. of the various regions. few years, with the design of By using internal frame stores The symbol of the world several electronic graphic devices, there is no restriction on the comprises three coloured parts. A a good relationship has developed colours, which can be properly gold shell, which is painted black between the two disciplines. While shaded. Since the colour inform- on the inside, with a shaded blue neither party fully understands ation is internally stored there is disc behind it. The sea areas are the restrictions and principles of no need for an external synthesiser etched away, leaving the land the other, each now has a good or clipper, thus reducing both day- masses highlighted in gold on the grasp. of one anothers limitations. to-day and long-term variations. outer surface, and black on the Interestingly this even transcends All National and Regional Centres inner surface. Where the shell is the use of jargon. which opt-out of BBC I have been completely transparent, that is provided with their own equipment Designs Department devel- where there is sea on the front and oped the principles of the system. whose outputs, apart from their back, then the shaded blue disc is The most important part of this customised caption, are all seen. The outside is highlighted to was the data compression format identical and of consistent quality. make it appear as though it is lit continued on page 8 'ENG /NF'Spring /985 - Page 1 \ Editorial I Do you cringe when you hear disc- jockeys refer to "97.5 FM" or "1548 kHz medium-wave"? (It is almost as infuriating as hearing ten pence referred to as ten pee!) These "station idents" as they are known, are intended to tell the audience which station they are listening to should they have tuned-in by chance. But they are, to say the least, contradictory, since 1548 kHz refers to frequency and not wavelength; similarly 97.5 refers to the VHF band and not to the modulation system. For those Brian Marsden (left) from GEC McMichael, and ADE, Charles Sandbank whose notes at Wood Norton have sign a licence agreement that allows GEC McMichael to manufacture and long since gathered dust in the market the CD3M/546 digital PAL decoder attic, the wavelength in metres disc-jockeys and presenters should it is likely that "FM" will be equals 300,000 divided by the use phrases that listeners are more adopted, and your editor will be frequency in kilohertz; thus familiar with. in a permanent state of cringe! 1548 kHz equals a wavelength of I~ an attempt to persuade Incidently, in technical writ- about 194 metres. The correct more hsteners to use Band 11,BBC ings it is right and proper to use phrases, from an engineer's point Radio has tried to formalize this VHF MF LF and HF when of view, are therefore "97.5 MHz situatio~, by sug~~s~ing that the refer;ing t~ frequencies, and FM, VHF and 1548 kHz medium phr~s~ VHF-F~ 1S used, thus AM, PCM, DPSK etc when referring frequency". However, research has aVOldmg a con~'hct between engin- to modulation systems. shown that very few radio receivers e~rs and the hsten~rs. .Eventually There are no prizes for (or should I call them sets?) have e1ther VHF or FM w1ll become guessing which service might carry tuning dials marked "VHF and normal as the listeners become a signal via NICAM 3/PCM, FM, MF"; they are far more likely to accustomed to the phraseology, and DPSK with C-MAC E-MAC be marked "FM and AM or MW". and the alternative phrase will be D2-MAC, or B-MAC in Band VI: Therefore it makes sense that the dropped. Sadly for the engineers, Answers on the back of a 500 pee note to my office please!

The Cost of ITV Alan Lafferty

The following article from Corporate Publicity provides some useful facts when discussing the BBC's finances: Transmitters Opened Figures provided by MEAL, the market research organisation, to the 'Did You See ?' programme on the financing of broadcasting (Sunday 10 February) show in detail the amounts paid by consumers towards ITV The following uhf transmitters and Channel 4 through the shopping basket. have opened since January: Out of a basket of everyday goods which cost a total of £6.20, the following amounts go towards the cost of television advertising: Upper Soudley Glos Occom be Valley Devon ( Chocolate 200 g 1.74 P Cheselbourne Dorset Crisps 150 g 0.84 p Bidston Merseyside Cereal 150 g 2.75 p St. Albans Herts Tea Bags 80 1.81 p Stokein teignhead Devon Cat Food 415 g 0.56 p Inverness Highland Soap 142 g 1.43p Gellifendigaid Mid. Glam Toothpaste 175 ml 8.28 p Tregynon Powys Stockcu bes 24 5.27 p Deodorant 150 p 8.91 p The following vhf transmitters have opened or changed: Total cost of products £6.20 31.59p to TV advertising costs Ludlow Salop MEAL reports that the most heavily advertised group of products are Brougher Mtn. Co. Fermanagh baby care items. A box of disposable nappies costing £3.25 contains in its Lame Co. Antrim price 47.61p for television advertising - 14.6% of its price. The price of a family car (1.6HL) includes £24.40 for television The following local radio trans- advertising. mitter has changed: All prices provided by MEAL include an allowance for airtime discounts and for agency commission'. Les Touillets Guernsey Cl Page 2 - 'ENC INF' Spring 1985 different ~upplier, and a different So, in 1979, a BBC specifi- TV 36 set of problems emerged. These cation for TV36 type cable was cables had all the same colour produced, this being coded Camera Cable insulation (white) on the inner PIF36/1M. Initially this specifi- conductors and sadly little cation called for three versions, A, One of the necessary parts of a attention was given to the B, and C (rubber, polyurethane television studio is the camera and allocation of conductor functions and pvc sheaths respectively). The lens, and a lot of time is spent or pin layout. Thus syncs could resulting cables were free of earlier maintaining and lining them up run next to talk-back circuits, problems of return loss, colour before use. In the last few years resul ting in a permanent buzz on coding of cores, and the lie of the however, one of the weak links in the cameraman's headphones. This cable. After further development a the chain has been the multi-core problem was particularly evident single cable, the 'D' version, with an camera cable, now known as on the Philips LDK series cameras. overall diameter of 17.5 mm, TV36, that connects the camera All TV36 cable up to this date sheathed in Arctic grade pvc, was to the studio control rooms. With was designed for use with baseband produced. This improved the recent modifications it is hoped frequencies, and it could ha.ve a flexibility and avoided the 'squeak' that the problems associated with poor return loss when multIp~ex problem which occurred on some the cable and its terminating signals up to 27 MHz were bemg studio floors with the polyurethane connector will be resolved. carried. Slight differences between sheathed cable. It was also thick F or non tv-studio engineers it manufacturers' designs resulted in enough to prevent it going under is perhaps worth considering what connectors that did not mate, pedestal guards. The 'D' version the cable does, and what the problems were. As the name suggests, the cable has thirty-six Outer inner core conductors carrying the cover Clar;nping Groove for moulding camera picture outputs, camera s~:~~s locat!ng controls, talk-back and intercom, clamping . Clamp nut syncs etc. between the studio or OB and production control areas. A cross-section through the cable shows its complexity. The cables first came into ""' = widespread service with the Link 110 camera, and came complete 0 oD with termina ting connectors at \ each end. These could be straight \ Re~ning pin . / for hexagon a I \ entry or angled entry connectors Shell housing Gasket insert ComJ;lression depending on their application. ' Shell housing _ \ nng Two problems came to light; Shell housing the drain wire, a solid conductor, retaining screws kept snapping every few inches; the g symptoms being a shower of bits of conductor falling out of the cable when it was opened up. Secondly although some of the clamping became, and remains, the standard the clamps at the rear of the arrangements were better. How- TV36 camera cable for both studio connector were inadeq uate and the ever, clamping still caused trouble and OB use. compression ring lasted only about on the studio floor - the cable However, cable clamping was a month before becoming too tired would frequently be pulled out of still a problem as under severe for further use. the clamp when the camera conditions, the original compress- So the BBC turned to a moved, and the clamp came off on ion ring clamps deformed the cable the studio catherine wheel. The evenly all around the ring, leaving original studio floor cables came it free to move slightly. Eventually covered in neoprene which ripped the wires of the outer wire braiding off if the cables became trapped snapped off their anchorage, and under the camera pedestal wheels. the inner wires broke off the Although the neoprene was flexible connector pins: the evidence of and quiet when moved on the this starting to happen was felt studio floor, it was "sticky" and when the connector clamps could picked up dirt. An extra wire, be turned slightly on the cable sometimes carrying power to end. SCPD produced a clamping camera lamps, was wrapped round wedge as an interim solution which it to lift it out of the dirt. Poly- was inserted into the clamping shell urethene was tried as a sheath and held the cable firm. This instead, but this stiffened the worked by flattening the cable cable and had the nasty habit slightly, but the whole clamping of producing loud squeaks in the assembly then tended to unscrew Cable cross-section middle of productions, although it from the body of the connector. seen from socket end proved satisfactory for use on OBs, The wedge modification and for wall mounted cables in works well if the clamp assembly studios. continued on page 9 'ENG INF' Spring .1985 - Page 3 Improved Videotape Editing

Soon after the introduction of . .;'., '';~/:~:.~~::~f~.~~\.-.~ EBD time and control code (time- .,..i,~;;t~JRU~::"'f;\t';" code) it became apparent that there were two levels of vt editing. Whereas the day-to-day require- ments of actuality and sports 11 EI'- : programmes could be met by a two-machine edit system, the more complex drama and light enter- tainment productions required a three-machine set-up (two play- back, one edit). The DEC LSI 11/23 computer Current examples of these load edit data into Electra to give edit points by reviewing the VHS systems, both designed by Designs rapid re-location of edits. tape, and, using the slow mode Department are known as and 'still-frame', to allow precise ELECTRA and EDITRACE. Edit List in Sypher time code values to be logged. More The Electra system is designed It is also proposed to use the disc recently some editors have used to control one edit and up to three in the Sypher sound dubbing suite, the BBC Microcomputer to log playback vtrs on an edit-by-edit where the programme sound of these timecode values, and using a basis. Previously the internal data the eqited videotape is improved suitable program, an edit list is storage handled one edit sequence. by adding background effects, compiled which can then be However, this facility has been music, or inserting alternative printed out. However, by extend- extended now that external data material, and generally tidying up ing the Microcomputer program, it storage has been added. Data the sound which may only have can also be used to send the edit logging equipment known as been rough edited at the videotape list, in serial data form, directly to ELECTRALOG (RD3/501) has edit stage. Much of the sound ELECTRALOG. This work has been installed in the main video- work in Sypher is linked to the recently been completed and the tape edit suites at TV Centre. The vision edit points and the associa- first programme to use 'uploading' eq uipmen t provides automatic ted time code points of the original from the BBC Microcomputer to logging of all the edit decision material. If this data can be trans- ELECTRALOG was the compil- points (8-digi t timecode values) ferred directly from the disc to the ation of the test picture sequence, and associated data for the Electra audio-machine synchronisers, then fur fue EBD, of ~and~d~ (RD4/509) videotape edit control time is saved by not having to type converted hd tv tests. Seven systems. this data in. This proposal is now identical tapes had to be compiled The equipment includes two being progressed and a working from original material for control-panel modules which are system should be in service next distribution to the EBD members fitted to existing panels in the edit year. without using an intermediate dub. suite, a bought-in DEC LSI1I/23 Much time was saved by using an computer supplied by Dnit-C of Off-line Input to ELECTRALOG edit list compiled on the BBC Worthing, a vdu with many built-in ELECTRALOG will also accept Micro. This was loaded into display features, and an interface data in the form of a serial data- ELECTRALOG and the first tape panel between the computer and stream containing the time code edited. Several new edit points Electra. The data is logged on a edit points which have been were added during the session as 3'l2-inch floppy disc as the edit compiled from a VHS viewing copy well as changes to the original list. session progresses so that, at the of the original recording. The VHS ELECTRALOG built up a new list end of the session, a complete list copy has an 8-digit time-of-day as the session progressed, known is held on disc. If, at a later stage, timecode 'burnt-in' to the picture as the 'final' list. This was then re-editing of the programme is when the original recording is used to compile the remaining six req uired, the disc can be used to made. This is used to identify the tapes. Vertical Interval Timecode A further enhancement, to eliminate the typing-in of the 8- digit numbers from the VHS copy, is being developed. This will require vertical interval timecode (vitc) to be recorded with the vision signal on the VHS copy. The time-code o . . is normally recorded twice on two o O' television lines in each field blank- o. o . ing period. As well as the time . information within the code, there are eight 4-bit blocks of 'user bits' The Electralog interface unit which could be used to carry other Page 4 - 'ENG INF' Spring 1985 information such as the spool number. A vitc converter (CD4Sj 418) has been developed to insert vitc and 'burnt-in' timecode characters onto the vision signal when the recording is made on VHS. It decodes the input feed of longitudinal time code (carrying the time-of-day) which is distributed round the studio complex. A special vitc reader (CD3Sj 549) will send decoded vitc in serial data form to the BBC Microcomputer used to compile the edit list. Using still-frame mode on the VHS machine, a single key The playback control panel operation on the Microcomputer in some studios using a timecode reader with integral LED display the sequences is also logged in the and stopwatch facility to ease this 1111 a studio, as recording takes place, task. A specification has now been I by noting time-of-day against the agreed, and a new unit will be a 11 I developed based on a micro- .. script. Durations of items are timed using a stop watch. For some years processor which will then be now a trial has been taking place installed in all studios. Special Effects Compact Disc

BBC Radio has released a compact would normally have gone on to a disc of sound effects for in-house 7-inch disc. use. The disc is a 'pilot' for The new CD features a range evaluation by the sound effects of effects, to allow for as much service. experimentation as possible. There The editors control panel In radio and television, a are a number of backgrounds such 100,000 discs are issued on loan as sea wash, rivers and city skyline, will log the time code value from annually via the Sound Effects especially useful in CD quality, as the VHS. Centre. Each year a number of new well as new recordings of bicycles, If the VHS copy is edited in releases are added to the collection dentistry, babies and natural an off-line edit suite, the vitc will to keep it up to date. At present, history subjects. There are also be carried through to the edit tape. the BBC uses 7-inch 33 rpm discs some percussive 'spot' effects Several generations of editing can for its stereo recordings, with up which are usually difficult to put be carried out, and, by reading the to seven minutes material on each on to an analogue disc. ) vitc from the edited tape, an edit side. Through the audition It will be some time before list, including spool numbers, processes, and normal studio wear the sound effects service can obtain could be automatically compiled and tear, the surface quality enough feedback on the CD to on the Microcomputer by detecting. deteriorates and the life of the make detailed plans for the the vitc time discontinuities. record is short. future. They will be relying The Compact Disc is an htfavily on the responses of people Logging in the Studio attractive alternative in terms of involved in programme sound, in As the output from the studio is the economics of the sound effects both Radio and Television. Al- recorded onto the C-format service. One CD can have more though there is at present only a machine, time-of-day longitudinal than an hour's worth of material limited choice of suitable players time code is also recorded on track - four times as much as a 7-inch for CD reproduction, two studios three so that sequences and events disc - with a longer life, and a in Broadcasting House have been in the programme can be accurately bonus in terms of quality. equipped. located for editing. The timing of The Sound Effects CD has been pressed by NIMBUS RECORDS, the only UK manu- ***** facturing plant. Digital equipment ERRATUM was used to make new digital The credit for the photographs on recordings for three quarters of the the back page of 'Eng Inf'number playing time of the disc. The 19 was wrongly attributed to John material was assembled in-house Flewitt. The credit should have and digitally edited on to a U-matic been given to David Bruce Johnson cassette. The remaining playing of SCPD. time was taken up with new stereo Our apologies for any em- The video printer and binaural recordings which barrassment caused. 'ENG INF' Spring 1985 - Page 5 In troduction BBC Television's new Weather computer system, allows the Animated Graphics for Nf5 weathermen to construct high quality graphic sequences that describe how the weather is computer configured as a Weather 160Mbyte Winchester disc that changing over the United Kingdom. workstation. This controls soft- forms part of the Quantel display The system, developed in-house by ware running on a Digital Equip- subsystem. These frames are broad- the Computer Graphics Workshop, men t VAX 11/750 minicom pu ter. cast live from the Quantel which is uses the latest techniques in The VAX in turn controls a controlled by the weatherman in computer graphics to both prepare Quantel 700 I graphic terminal the studio using a second and display tv weather bulletins which generates the anima tion Macintosh XL. from data products produced by seq uences. the Meteorological Office com- The bulk of the data, i.e. Weather workstation puter centre at Bracknell. satellite images, forecast data The initial brief for the system designer required that the system be capable of one-man operation by the weathermen. It was realised at an early stage in the project that this would probably represent the greatest challenge to the software development team. Various man-machine inter- faces were evaluated and tested, including graphic tablets and joy- sticks, but the best method was found to be a "mouse". At that stage the only easily available system with good interactive graphic facilities was the Apple Lisa, now appropriately renamed the Macintosh XL. The implementation of this specialised user interface for the weather system represents a major step forward in man machine interfaces in the BBC. It allows the weathermen to see and edit a graphic representation of all the Weatherman Michael Fish rehearses in the studio. The Macintosh terminal digital weather products, the (right), is controlled by the switch in Michael's right hand satellite image sequences, and an updated version of the familiar All material produced by the products and weather statistics, computer system is presented etc. are sent from the Met Office using a uniq ue electronic black- computer to the VAX computer board. This new studio technique over British Telecom Kilostream allows the wea thermen to be in circuits. This processing proceeds vision simultaneously with the independently of other production graphics, and also lets them both work on the VAX system. The see, and control, their animation Quantel graphic facilities are sequences during the broadcast. augmented by a Jupiter 7 frame- The design of the familiar BBC store which assists in the processing Weather symbols has been im- of satellite pictures. proved, and wherever possible, all new map and satellite grids have BBC Computer system been cleverly designed to relate to The computer system at Television each other. The two graphic Centre uses a Digital Equipment designers on the project have also V AX /1/750 minicomputer with been able to take full advantage of 2M byte main memory, linked to the latest computer techniques in two Apple Macintosh XL micros digital typography and carto- with IMbyte memory each. The graphy. software running in these com- The system has taken just puters allo'ws weather data to be over one year to develop and builds received automatically from heavily on software experience Bracknell and also lets the weather- gained by the Computer Graphics men plan and view material. Workshop on the general election When enough material has and other similar projects. The been assembled, the video frames BBC end or the system uses an that constitute the final bulletin fan McCaskill and Michael Fish llse the mOl Apple Macintosh XL micro- are stored on the integral for the midday forecast Page 6 - 'ENC INF' Sllring J985 (cso), and video rear projection. The compu ter graphics are ~w TV Weather System projected onto a screen approx- imately the same size that viewers are familiar with. This image is sym bol chart. of the complete bulletin. tinted blue by spilling some blue Operation of the system in- light onto the rear of the screen. volves viewing various graphic Graphic displays and studio This allows the weatherman to menus, pointing with the mouse operation stand in front of the screen and d riven cursor, and selecting the All of the images and graphics are see a degraded version of the full desired object or command. For assem b led in the Quan tel 700 I colour image. The man can example, when the symbol chart is display sub-system. This sub- therefore point and gesture to being prepared, the Macintosh dis- system is a Motorola 68000 the visuals in a way which hitherto plays a set of iconic representations micro in which the low level was very difficult with cso. of clouds, sunshine, snow, rain and graphics software runs. The micro The camera viewing this scene hail symbols. By selecting these symbols and placing them on the appro- priate map background a complete chart layout is defined. When the time comes to make up the full symbol chart, the Macintosh sends a list of the chosen symbols and their position to the VAX which instructs the Quantel what to do. This operation is very speedy and if need be the Weathermen can make up a sequence of symbol charts which can themselves form a short animation sequence. Similar techniques have also been implemented to help edit the positions of highs and lows on the isobaric charts, and to allow the weathermen to draw warm, cold and occluded fronts. Since a nother part of the brief demanded that the format of each day's bulletin would be flexible, an interactive sequence editing Photographed "off-the-tube ", how the presenter and graphics fit together facility has also been provided using a "filmstrip" representation also controls two broadcast quality is locked-off, and sees the wea ther- framestores, a local 160Mbyte man against the blue-background. 1:/' Winchester disc which stores The viewer at home, however. sees ~ ~ pictures, as well as communicating the weatherman in full colour in . .' " . " to the VAX. front of what appear to be full tID I colour weather charts. The :.a.f ~ '" .L Almost all of the graphic , weatherman controls the whole _ ~l_ j. output techniques used within the . show through one push button ~ . project were originally developed by the Workshop for use within and can therefore interact wi th real-time projects such as the the graphics even though they General Election, 1984 European may be animating. and US Elections, 1984 Olympics, the Money Programme, and Odd Bracknell Computer Data One Out. All of these have a The BBC is the first UK broad- requirement for high quality text caster to subscribe to the new and/or maps whose layout and digital weather product service design can be predicted well in offered by the Meteorological advance. Office. This service relies on one The system heavily exploits of the most powerful computers the unique facilities for mixing in Europe, a Control Data Cyber between framestores to animate 205, located at Bracknell. multiple satellite images and the The Bracknell system sends forecast products. three types of data to Television The studio presentation by Centre: satellite images: forecast which the weatherman delivers his frames for various weather bulletin is completely new. The phenomena: statistics on rain- :lse to select and place symbols techniq ue is a hybrid one, relying fall and sunshine for the previous on both colour separation overlay continued on page 9 'ENG fNF' Spring 1985 - Page 7 New World -continued from page 1 pixel definitions. There is physical customising for each region affects for storing the map of the world space for up to 7.5 Mbytes of only the data on two cards in the at all angles. The hardware de- memory, although the addressing system. In fact, since only the velopment included EPROM based can access up to 16 Mbytes. For caption is different for each, only frame-stores, and digital processing this application a field of data is 16 EPROMs are specialised. of the video. Software had to be stored in less than 8 kbytes of The controller also decodes written for the departmental memory space, as opposed to over the sequence data from its highly VAX-Il computer for validating 400 kbytes for a full field store. compressed format into a usable and processing the data into a 13.5 MHz data stream, and suitable form for direct program- Software distributes timing information to ming into memory. The starting point for the sequence the rest of the system. Timing A third group in the project data was a purchased data-base of control is useful, since it can was Computer Graphics. They have a Mercator's projection map of the eliminate the need for external been extensively involved in- past world. This was edited by synchronising. This equipment's projects, and for the BBC 1 symbol Computer Graphics to remove all ou tpu t can be varied from over they wrote large amounts of soft- political boundaries, and trans- 6ps early to over 3ps late relative ware, especially to generate the ferred from their VAX-ll com- to the mixed syncs input reference. compressed data for each view of puter into the Quantel Paintbox. Digital multipliers are used to the world. This processing and This was used for a 2: 1 size re- key the map onto the foreground the transferring of data between duction which incorporated the and background data streams. their Quantel and VAX-ll anti-aliassing algorithms. The data These are full 8 x 8 bit devices, computer took a long time and was then transferred back to the and correct scaling is incorporated was mostly run over weekends, VAX for encoding into the Designs to ensure unity gain where but the time had to be carefully Department data compression necessary. The two keys are chosen so as not to interfere with format. processed to prevent any excess election coverage in 1983 and later The two sets of fixed data, the amplitude after combining. the Olympic games. gold shell for the foreground and The two data streams are Computer Graphics also the blue disc with caption for the added digitally, before being organised some early feasibility background, were 'drawn' on the blanked. Normally digital blanking studies to evaluate the graphic paintbox. This data is properly needs to be shaped to conform to principles. In particular this anti-aliassed at source and was also PAL system I, but since all the showed that a 3D effect could be transferred to their VAX-I1. signals are generated internally, obtained even with an 'infinity' Further processing ensures that no correct shaping is naturally view. degradation occurs. included within the data. (In any The digital standard used is Both the fixed and sequence case the start and end of all lines that specified by the EBU for a data was transferred from are black.) digital parallel interface. While the Computer Graphics to Design A new, triple-video, analogue- device has only analogue outputs, Department on magnetic tape, to-digital converter has been to suit present installations, the using the internal post! This proved designed to provide the YUV EBU specification defines the to be an extremely efficient outputs and an analogue matrix required sampling rates and levels method of data interchange, far used for two sets of RGB outputs. for luminance and chrominance. A exceeding the earlier methods of Both these units employ close further advantage is that the paper tape and floppy disks. tolerance components to minimise Quantel Paintbox handles data in drift, and hence regular alignment. a form quite close, but not Hard ware A test waveform is included within identical, to this format. The memory structure is similar to the system for checking output To produce the overall effect that used for the recently intro- levels and matrix accuracy. two full frame-stores are used. duced digital Test Card F generator The system also includes a One is the foreground store which (see Eng Inf No 18), but each card large power supplier, based on a holds the highlighted gold shell, can hold more data, and can be a commercial unit, and a BBC and the other is the background part of a larger data-base. The designed clock generator which is store for the shaded blue disc and EPROMs used are 27128 16 kbyte common with other digital the captions. These stores hold devices, although the memory card equipments. only a single frame, and there is can take 27256 and even 27512 no restriction on their content. devices as, and when, they become Manufacturing They are full colour and can available. When fully populated The detailed design of the system display any picture produced by with 27128s each card holds began in early 1984, with the re- the Quantel Paintbox. These stores 0.5 Mbytes. quirement that the new symbol are generally known as the 'fixed' The controller unit has a should be ready to go on air by memory. 24-bit sequence address bus giving 1st January 1985. This included The main store of the system access to 16 Mbytes, but the the slight complication that not is known as the 'sequence' equipment has space for only only London, but also eleven memory. This holds the data for 7.5 Mbytes, and is fitted for regions had to have their the map of the world for each of 5 Mbytes. The controller also equipments delivered and installed the 600 fields that are displayed. addresses the fixed memory well before Christmas. This data is compressed by a coding through a 19-bit address bus. This Taking a certain amount of system which combines the memory uses identical cards to the risk, some manufacturing had to benefits of traditional run-length sequence memory and four are in be initiated before the prototype coding, with the advantages of parallel. A result of this is that the was fully operative. This partic- Page 8 - 'ENG INF' Spring 1985 . ularly applied to the making of Perhaps the most time con- components despite shortages. In over 200 memory cards. Existing suming part was the programming particular we received a great deal designs and the large quantity of of nearly 6000 EPROMs. This was of help from Valve Section, who memory units were made by facilitated by the purchase of two managed to buy 6000 EPROMs in Equipment Department, while the specialised MOS PROM pro- a depleted market being scoured rest, including the crates, were grammers. One could be connected by the hungry computer industry! made by the Production Unit of through a terminal to receive data The end result is a successful Designs Department. The manu- direct from the departmental example of co-operation between facturing process and system test- VAX computer, while the other artists, programmers and engineers. ing went quite smoothly and all could copy ten devices from a The mutual respect between these the regional units were delivered master EPROM. Without the VAX parties has been fostered over in N ovem ber. facility, or something of similar several projects in the past, and it All the digital cards that were power and capacity, it would is to be hoped that it shall continue designed for the system were probably not have been possible in the future. prototyped and proven using the to complete the software process- The techniques developed for wire-wrap techniq ue. They were ing in the required timescale. For this project have applications for then laid out for pcb's using example, more than five days of the future, and we can look Designs Department's Racal Cadet CPU time was used to process just forward to new devices using CAD system. Without this, it the background data for all similar hardware and data would probably not have been regions. preparation. possible to obtain the component and interconnection density. Summary by Brian Mason, D.D. Certainly the accuracy of the This complex digital project has computer-generated artwork been successfully completed on ensured high quality products time. We were, to a certain extent, requiring the minimum of fault fortunate in being able to obtain finding during test. the required number of some

TV 36 Camera Cable In 1984 Equipment Depart- the connector during routine continued from page 3 ment produced a redesigned cable maintenance, and, if necessary, clamp, but it can only be used by using a fair dose of the correct is screwed tightly into the con- severing the ends of the cable and grade of Loctite to ensure that it nector body and suitable Loctite starting again! However, the clamp remains that way. (Bearing in is applied to stop it working loose. will still unscrew from the mind that one day it may be This adaptation can. be easily connector body unless it is firmly necessary to unscrew it!). retrofitted to BBC or BICC made glued on. The plain washers and When ordering parts for cable cables but not those made by BIW. compression ring shown on the assemblies it is worth noting that Modification kits are available at diagram have been replaced with a several manufacturers have been Equipment Department; contact tapered wedge. The modifications involved. Parts for, say, a BIW Colin Smith for further inform- have all but cured the problems, assembly may not work with the ation. but it is still worth checking that ED system. the clamp is screwed tightly into

New Weather System continued from page 7 day. In the future it is expected re-projected to a form suitable for isobars for up to 36 hours ahead that rain radar products will also the BBC, and transmitted to and longer if required. be made available. Television Centre in a compressed In addition the model can also run-length code over BT circuits. predict wind strengths and Satellite images The images are re-generated in the direction, plus relative humidity The satellite images originate from VAX computer, and sent via a and several other weather the scanners on-board the Meteosat DMA data link to the Jupiter. The phenomena. This data is encoded geostationary satellite. Before video output of the Jupiter is fed in a metafile, Le. a compact set of reaching Television Centre the as an overlay to the Quantel which drawing commands and sent in the images are first received in "prints" this on the appropriate same datastream as the satellite Darmstadt, West Germany and map background. Images. processed into a digital datastream, When these are received by retransmitted to the satellite and Forecast products the VAX at Television Centre then bounced to the Lasham The forecast products are derived these commands are translated ground station. From Lasham they from the model of the atmosphere into a form suitable for driving the are then sent in analogue form to which runs in the Cyber 205 which Quantel 7001 which is con figured Bracknell where they are converted is regularily fed by a considerable to plot complex curves, typeset to digital form. number of observed weather data text and symbols. Once in digital form the values. The model is able to pre- images are made into a mosaic, dict and plot pressure values as 'ENG INF' Spring 1985 - Page 9 New Steerable HF Monitoring Array by Adrian Robinson, RD electrically. The phased array is signal, and this makes the new The hf broadcast bands are greatly arranged to have a beam which array more flexible than a set of congested, and often the quality of can be steered in any direction. In fixed directional aerials. The reception is seriously degraded by addition, a null can be steered operator steers the array and the interference from unwanted against a particular interfering null by means of two control stations. This causes difficulties for -- the BBC Monitoring Service at Caversham. Taking advantage of the fact that the interference is usually coming from a different direction from the wanted signal a directional receiving aerial has been designed to pick out the wanted signal. At the receiving site at Crowsley Park near Caversham, there is a large collection of aerials, each pointing in a fixed direction, and this takes up a lot of space. What was needed was a mechanically steerable directional aerial, but this would be unwieldy, so a new type of receiving aerial system has been produced by Research Department which has been used experimentally for some years with good results. The new system uses eight small aerials arranged in a line. The signals from the aerials are com- 1.....__I bined through variable delay lines so that the directional properties Adrian Robinson setting up the new aerial array at Kingswood Warren of the array can be adjusted before despatch to Crowsley

with PAL decoders and were able Digital PAL-ta-PAL Transcoder to synchronise almost any signal - including those from recorders - by S J Auty DD PAL" processing, that is they without time base correctors. and B A Roberts SCPD digitise the PAL signal as a single Designs Department were More Complicated Operations data-stream with a sampling clock asked to design a simplified version The increasing complexity of locked to the colour subcarrier. of the SECAM to PAL Transcoder television programmes creates a This technique has not been suitable for synchronising PAL demand for more technical re- entirely satisfactory because of signals alone, because no com- sources and greater flexibility in errors in the sub carrier-frequency mercial component synchroniser their deployment. More incoming to line-frequency relationship, and without "effects" facilities, (which circuits to Studio Centres are certain difficulties of instrumen- are not needed for this appli- necessary, and complex effects tation, which cause the output cation), is available at a reasonable req uire the signals to be syn- picture to hop about. price. chronous at the vision mixer. These problems can be avoid- The result is the PAL TO Because of this it was decided ed by using "component" digital PAL TRANSCODER (C06/511). that in future almost all sources on processing, where the PAL signal Equipment Department have just the TVC main routing system is decoded into its luminance and finished making three of these, and should be able to be made syn- two colour-difference components. they are now being installed in the chronous. Outside Broadcasts have The components are re-timed to Central Apparatus Room at Tele- their own complex locking arrange- the required output-pulse chain, vision Centre. They are fitted to ments, and it is no longer practical and then fed to a PAL coder to three of the outputs of a new to slavelock them at TVC. make the output signal. Auxiliary Routing Matrix so that Some years ago Designs De- any incoming circuit can be made Digital Synchronisers partment made two SECAM to synchronous. In fact as several Commercially produced digital PAL Transcoders for the television destinations can select the same synchronisers have been used to service which do just that - except incoming line source and can either solve this problem in the past.. that the decoder is for SECAM not be made synchronous with two These eq uipments use "composite PAL. These equipments were fitted different pulse chains simultane- Page 10 - 'ENG INF'Spring 1985 knobs, and a microprocessor calculates the necessary delay-line lengths. The users of the array have found its directional properties valuable, especially the amount of control available over. the directional pa ttem. On a num ber of occasions the array has success- fully produced a readable signal, when the same signal was unusable owing to interference when received on any of the other aerials. However, several improve- ments were suggested by the operators and, as a result, an improved system, 'The Mark II', was built at Research Department by Adrian Robinson and Bob Day. The new array in use at Crowsley Park It was installed at Crowsley Park by Allan Fraser of TCPD, and is operat?r had to set th~ required reed relays had failed. By feeding now in operation. operatmg frequency. ThIS has now direct current through the system, This has several new features. been automated so that the array the array is provided with a self- The reed relays, used to control the interrogates the hf receiver direct- checking mechanism, and the reed delay lines, produced a series of ly. All the relevant information is relays are provided with a "wettino- clicks when the direction of the available to the operator via the current" which significantlY array was changed. In 'The ?perator's control box, as shown improves their reliability. First Mark II' these clicks have been m the photograph. Also, there was impressions, by the operational suppressed, making listening much no way of knowing if part of staff at Crowsley Park, are that easier. the system had a fault; for the array is much more user The calculations for the null example, if the aerial cables had friendly. are frequency dependent, thus the been cut by a lawnmower, or the ously, or with two destinations output which matters - it is the Analogue Transversal Filters using the same pulse chain. quality of the result of recoding A major difficulty with the bald those components to PAL. decoder is the ringing (short-term PAL Decoders The bald decoder uses con- echoes) caused by the luminance Clearly the PAL decoder at the ventional high-pass and low-pass low-pass filter. Designs Department synchroniser's input must be of the filters to separate the PAL into have developed a novel solution to highest possible quality. It must chrominance and luminance com- this problem by making a trans- completely remove all traces of the ponents respectively. The output versal filter, which operates by input subcarrier, or highly ob- luminance component contains no combining signals from several taps jectionable interference with the high frequencies (fine detail) and on a delay-line. The delay-line is differently phased output sub- the chrominance components con- unterminated, and an input wave- carrier will result - the so-called tain a lot of cross-colour (spurious form appears twice at each tap - PAL footprint effects. colour information caused by fine once on its way down the line, The obvious choice, you luminance detail). However, when and a second time on its way back might think, would be one of the the two are combined in the out- after being reflected from the un- line-delay-based comb-filter de- pu t PAL coder the cross-colour is terminated end of the line. coders which are now available. transformed back into fine This filter is designed to However, subjective tests by luminance detail, which replaces behave a bit like an aperture Designs Department have shown that lost in the low-pass filter. corrector and produces far less that better results can be obtained This process is not perfect; ringing than conventional types. on most pictures with a much for example, the limited chrom- simpler decoder, with a price about inance bandwidth of PAL means Do You Need A PAL one third that of a combing- that some fine detail is lost. But Synchroniser? decoder. comb-filter decoders are not The PAL to PAL Transcoder (C06/512) is now available from perfect either - they attenuate The Bald Decoder fine diagonal luminance severely. Equipment Department. They will The important point is that it is Subjectively the bald decoder is be happy to receive your order. not the intrinsic quality of the better on most pictures. component signals at the decoder's 'ENG INF'Spring 1985 - Page 11 House of Lords First Live Television Debate

The first live televised debate from chamber is cross-lit with five the House of Lords took place on fittings on each side. January 23rd, the culmination of The lighting level is low by several months planning by normal television standards being Television Projects, and Television only 350 lux. At the request of the Outside Broadcasts. Political con- House of Lords, a special dimmer siderations apart, the main diffi- system has been installed that culty was to demonstrate to their brings the lights up slowly over a Lordships that the level of ligh ting period of three to five minutes. would not be too obtrusive. There- Thus their Lordships are not fore a series of demonstrations disturbed by a sudden increase in were made to the Select Committee light level in the middle of a who had insisted that no direct debate. Similarly it was agreed light should fall on members faces. that the lights would not be The Committee opted for a soft- dimmed in the middle of a speech. lighting system proposed by the Natural breaks in the proceedings BBC using Lee Electric lights as a are used to dim the lights. basis. Ten fittings were manu- Once approval had been factured in the Television Outside granted for the lighting system, the Broadcast workshops at Kendal remainder of the rigging could Avenue and the whole rig demon- commence. Cabling for up to five strated to the full House of Lords permanent camera positions was when they debated the Select hidden under the floor of the Committee's report in November House, with a camera position 1984. The demonstrations were fixed in each corner, and a fifth in successful, with Lord Whitelaw the gallery. All are inside the quipping tha t for the first time he chamber, but outside the bar of could read his notes! the House. The whole system was I 1 1 ...~.

The camera alld lighting are tested in the House of Lords

The lamps chosen are based tested on January 17th. their commercial colleagues in on the well known "6-lite", but the The sound feed is taken from ITN. Furthermore, it was agreed six PAR 36 (tungsten) lamps are the existing Tannoy/Hansard in- that there would be a full exchange mounted horizontally. A 50% stallation which is also used for of material by each of the diffuser is placed in front of each Radio broadcasts but is not under organisations. Technical cover is fitting to obtain the soft lighting the direct control of the Broad- provided on a rota basis with strict requirement. Each of the ten fitt- casters. A forest of microphones alternation between the BBC and ings has six 650 watt lamps, a load are suspended in the chamber, and ITN, a system that has worked well of 3.9 KW for each fitting, a tota'l faded up individually for the so far. of 39 KW for the overall rig. The Hansard reporters. This creat.~d Page 12 - 'ENG IN F'Spring 1985 Published by Engineering Information, & Printed by Engineering Training Dept.