The Domesday Device
Contents
1. via an infra red remote handset or via an RS232 link and of course has its SCSI interface built in which links directly to an onboard computer system In addition the player has a Gen lock card onboard which locks the video signals from the BBC micro and the LVROM player together so that video mixing is possible and a video mixer card The Domesday discs While the rest of the package is hardware capable of supporting a number of Laser vision discs the Domesday discs are a new breed called a LV ROM disc The ROM part of the title comes from the fact that all Laservision discs are read only so the information on the disc cannot be altered There can be four things on any LV ROM disc moving pictures a soundtrack 82 with two channels available still frames pictures or data for text graphs program code etc The clever idea seems to be that data can exist on an LV ROM disc in the channels allocated to sound This means that while the number of picture frames can be of the order of 54 000 frames per side the amount of computer readable data can be immense up to an incredible 350Mbytes per side the equivalent of about 600 ADFS floppy discs When you consider that most amateur users would have difficulty in ever filling a 30Mb Winchester hard disc with day to day usage the size of the LV ROM disc becomes astonishing Have you noticed though how technology is cyclic Remember when you had to turn tapes over t2. wait the few moments until the start up message appears To be honest the start up session seems the weakest part of the system Several times the disc started and ran like a laserdisc player running a movie It has to do this to begin with but the computer should stop it A further CTRL Q Break Shift Break cured this in all but one case where a total power down was needed One old two months system which I played with took three minutes to start up and you can imagine the concern we felt especially as there was no screen message for most of the start up time I eventually put this down to coldness and it seems that the LV ROM player must be switched on and allowed time to physically warm up The VFS ROM Everything that happens in the system is controlled by the VFS ROM which true to Acorn format is compatible with most other filing systems I noticed that there were even a few spare bytes for acknow ledgements in the ROM a sure sign that the writers have a degree of pride in their work Inside the VFS are four major services the VFS proper the video control system the mouse control system and the trackerball control system The VFS behaves much like a read only version of the ADFS Although AIV sys tems can be organised with pathnames just like ADFS the Domesday system has everything in one directory Some of the VFS commands are of little use and others appear spurious because of the way in which users will w
3. 3 on CHAPTER lt digits gt Plays chapter s EJECT FAST lt dir gt Cue or Review FCODE lt string gt FRAME lt no gt PLAY lt start gt lt end gt Plays from sta rt to end NB PLAY lt RETURN gt plays from cur rent frame RESET SEARCH lt no gt As FRAME but no wai t SLOW lt speed gt lt dir gt Speed from 5 slow to 253 fast STEP lt 1 0 255 gt Stop step player STILL as FRAME VOCOMPUTER computer to VDU VODISC LY to VDU VOHIGHLIGHT Computer colour highl ights LV VOSUPERIMPOSE Computer over LV VOTRANSPARENT LV amp Computer mixed VP lt digit gt Figure 1 The available video commands and then display the result Pictures drawn like this can be quite enthralling and are well worth attempting The TMAX command needs a little more explanation There are four separate pointer shapes a cross a magnifying glass a northwest pointing arrow and a north east pointing arrow These exist in four quadrants The cross over between quadrants can be set anywhere relative to the actual screen The purpose of the TMAX x y command is to set the point on the screen where the pointer shape changes without having to continually monitor the position in the current high level language The video commands Figure 1 explains the video commands available which allow control over the AIV player With the Domesday disc the CHAPTER command seems redundant and in general terms the FCODE command is more usef
4. AIV The uptake of Domesday AIV discs has yet to enter the 100 000s and many companies are exploring other avenues of optical data storage particularly the CD ROM storage which has tumbled in price because of the mass uptake of CD players However there are several projects on the way which support AIV players and these projects should more clearly define the uses to which this newest of new technology can be put Until then here is a little problem for you to solve Using Logo and the Domesday national disc write a microworld tool which demon strates a set of colour photographs concern ing clothing Begin your first frame store TO KNICKERS Best of luck in exploring the fascinating world of the Domesday discs 85
5. Also it has gaps and although it won t go far enough into detail over some things it goes into far too much depth over others We desperately need more experience of using interactive video so I ask readers of this column to write in with their sugges tions for and experiences of using Domes ACORN USER JULY 1987 Joe Telford Domesday Gallery The hardware Laserdisc player and Master day in particular and IV in general Try to group the uses under three headings educational uses industrial uses and public uses Let s see what we can come up with but remember to test your application with some simple rules m Can it be done in another way more economically or more effectively m Will using it encourage interaction be tween people m Does it matter that the information is not first hand or up to date mg What sort of thinking is the system supporting Revision Problem solving Explorative The system itself The Master AIV system comes as a five part package which includes the Master 128 with 65C102 Turbo co processor an Acorn trackerball a Philips RGB colour monitor a Philips LV ROM player the Domesday discs and all connecting cables and manuals The Master 128 Turbo is a specially modified model which has a wide 50 way ribbon cable attached to its rear This is an SCSI Small Computer Systems Interface cable which connects to the LV ROM player and allows the Master to take control of th
6. R ACORN USER JULY 1987 1 THE MAIN TRACKERBALL COMMANDS Turns on the trackerball software Turns it off Sets pointer to location x y with default at screen centre Sets screen location for original of icons Displays moving pointer Erases pointer Erases and halts pointer Displays and halts pointer Returns value of TMAX x y 5 6 Returns current x y position Returns state of the 3 buttons Button 1 Return 2 TAB 4 CHR 192 2 THE BASIC PROCEDURES AND THEIR FUNCTIONS Plays from start to end Shows Frame no Fast forwards the player until Halts the player Fast rewinds the player until PROChalt Selects sound turns sound off Slow forwards the player till PROChalt Slow rewinds the player till PROChalt Steps disc shown in direction given Selects computer and video pictures Selects video highlighted by computer Selects computer output only Selects video output only Function Slow rewind of player Slow forward of player Slow fwd bwd 1 255 Returns 256 1 to 50 Returns 1 to 50 Stops player Plays fast forward Plays fast backward Steps in dir 1 to 50 frames Returns 3 Returns 0 Turns audio on off Displays frame no Plays from start frame to end frame Blanks screen then ejects disc Video from player only Video from computer only Player video highlighted by computer Computer and player equal video JOE S JOTTINGS styles available in Logo Listings 4 a
7. THE DOMESDAY JOE S JOTTINGS DEVICE Interactive video used to be slow and cumbersome but laser technology has changed all that y previous experience of in teractive video IV had come from building a VHS video tape interface in 1981 and writing software to make an early Beeb fast forward to frames and fast rewind to the start of passages This was an inaccurate and feeble attempt which only served to convince me that interactive video was at that stage both cumbersome and boring The chance to play with an early Acorn IV system in 1985 amused me further as the only available disc seemed to be a BBC wildlife programme about birds The operating system for the IV disc was quite tedious to integrate into any sensible language though the few children to whom I showed the disc felt that the way ahead for them was Logo interfaced to the service ROM in the machine Why interactive video One of the activities I really enjoy is messing with an applications based package to see what makes it tick You can imagine how I felt when news of the Domesday System filtered through and I with many others watched demonstrations asked key questions and tried to imagine what I could do with it Several months later I can drive the beast from its applications based software and from my usual languages The question of what to do with it is still hard to answer possibly because I think it s essentially a historical archive
8. e LV ROM player s functions But the Master can also be used as a normal micro running all the packages just like a standard Master 128 The trackerball which looks rather like a Marconi trackerball with an added Sticker fits into the Master s User Port and sits easily on the right of the computer It can also be lap held so you can use the system from a distance The colour monitor is a medium resolu tion model which is very easy on the eyes It has full screen control from easily accessible knobs and has a Euroconnector for proper colour you know the sort you get on TVs with not just eight colours but the whole range of shades and hues This is sometimes 81 JOE S JOTTINGS ASST Sicss Yorki Leeds om Manchester ba Shotfield Leicester r Birmingham Norwicha gt Coventry Aberystwyth e ipswich j Cambridge RT Swansea y Oxford London r AA poeanana e Canterbury from the University he sequence above shows the power of the system Using the mouse you can zoom in on any area Canterbury in the example in both maps and sattelite pictures Many pages of descriptive text are also available written by local school children and ground level photographs of each area known as linear RGB compared with the TTL RGB of conventional models The LV ROM player is easily the heaviest part of the package because in addition to being a Laservision disc player this beast is programmable
9. nd 5 are a simple Logo Microworld which performs the set piece of a trip to Telford Towers using the north side of the Community disc The annotated journey is in a long procedure called JOURNEY 1 Any words which you don t recognise as Logo primitives are defined elsewhere either as part of the frame database the general library or in the utility words of listing 5 Observe particularly the use of the Logo commands UKSATPIC BLOCKNORTH This shows how easily the frame can be overlaid with turtle graphics If the major tools are provided then the frames can be created simply by exploring the disc using its onboard software and noting the frame number of any interesting page For exam ple the hamlet outside Telford Towers is on frame 13857 so we can store this frame in Logo with a simple procedure TO TOWERS FRAME 13857 END Even young children are able to build up set pieces in this way and some can handle text and turtle graphics input to design multimedia displays The Logo words used in listing 5 are also shown in table 3 They cover the same procedures as the Basic procedures men tioned earlier but are much more elegant These utility words can be easily used to build up your own microworld set pieces like listing 4 or to explore the Domesday discs by entering commands such as FRAME 17337 The future of Al video With current costs as high as they are there must be some concern over the future of
10. o read the other track Well that s just what you have to do with the LV ROM discs The Domesday system comes with a total potential capacity of about 1400Mb of which about half is filled Future discs might be expected to be chock full of data The Domesday discs also come with a rather good user manual It s a tribute to good writing style and a very powerful and friendly system interface that most people can read pages nine 10 and 11 of the manual then throw it away Though to be honest the remaining 240 or so pages are worth reading just to improve your confidence that you are pressing the right buttons The remainder of the pack is made up of leads which are all sensibly fitted with plugs and there should be no problem plugging everything together The one point which has to be made 1s look at the diagrams the RGB lead connects the Master to the LV ROM player and the Euroconnector connects the LV ROM player to the monitor A further manual the AIV User Guide emphasises this and gives a clear if more technical explanation of how the system works Starting up Once the system is plugged together it can be brought to life by switching on and pressing CTRL Q Break This results in a message indicating that a video filing system ACORN USER JULY 1987 VES is in operating and this is the route in for the Fraternity of Hackers More re spectable application users will want to continue with Shift Break and
11. ork with the AIV system Certainly I could not find much real use for BACK DIR BYE DISMOUNT LCAT LIB MOUNT and MAP Although the VFS does not indicate their availability users can apply the usual FS commands like DUMBP LOAD TYPE LOAD and the OPENIN UP BGET BPUT and PTR commands of Basic On the track of a mouse The differences between the mouse and trackerball are apparently cosmetic except that the internal hardware of a Marconi trackerball differs from that of an AMX mouse The facilities available would bear use on any desktop and it s a great pity that Acorn didn t squeeze them into every Master Table 1 shows the main trackerball ACORN USER JULY 1987 commands remember that the mouse commands are identical The simplest commands can draw some very powerful graphics Look at Listing 1 in the Yellow Pages the mouse drawing program This allows a mouse or trackerball to move and draw pictures Notice that the pointer is turned off before drawing happens This is so the lines aren t drawn over the mouse Notice too that the pointer is switched back on in each loop Listing may seem quite simple but try calling up one of the video frames and then use the program to draw around the key shapes in the picture and save the result as an outline drawing Now enter one of the graphics packs currently available and fill in the outlines with various colours and tones AUDIO lt 0 3 gt O off
12. rn that people have raised about the Domesday system is that it is archival and hence the techniques used are more akin to data handling than to programming But still many teachers have suggested that there would be a lot of value in children exploring AIV discs and designing set pieces to answer a particular question or to demonstrate a particular item which needs multiple frames The whole idea of Logo as a presentation aid for AIV is quite exciting because a suitable Logo microworld might include tools for exploring the disc for storing frames by name for replaying set pieces and for asking questions about still frames In addition we might consider linking AIV to language maths and problem solving activities with Logo using branching adventure stories descriptive writing eg catalogues and turtle graphics for drawing on frames along with other useful learning 83 TRACKERBALL 1 TRACKERBALL 0 TISEI x y TMAX x y POINTER 1 POINTER 0 POINTER 2 POINTER 3 ADVAL 5 ADVAL 6 ADVAL 7 ADVAL 8 ADVAL 9 PROCplay start end PROCframe no PROCffwd PROChalt PROCfbwd PROCaudio ON OFF PROCsfwd PROCsbwd PROC step FWD BWD 0 50 PROCboth PROChighl PROCcomputer PROCvdisc 3 THE LOGO WORDS USED Logo word SFWD SLOW 1 255 BWD 1 50 FWD 1 50 HALT FFWD FBWD STEP FWD BWD 1 50 ON OFF AUDIO ON OFF FRAME no PLAY start end FINISH VDISC COMPUTE
13. ul to specialist applications and JOE S JOTTINGS can be ignored in many simple programs The set of VO commands are versions of the VP command with different digits for example VP 2 is the same command as VOCOMPUTER Particularly interesting commands in clude PLAY which plays forwards or backwards STEP which moves forwards or backwards from one to 50 frames in an instant and FRAME which selects a nominated frame Interfacing video to Basic Listings 2 and 3 include a set of Basic library routines listing 3 and a demonstration program listing 2 which explores the facilities of the AIV disc The best way to explore the library routines is to read listing 2 and follow each PROC call to its DEFPROC in listing 3 apart from PROCm PROCloop and PROCdelay which are all included in listing 2 Notice that PROCaudio and PROCstep require strings of ON or OFF and FWD or BWD respectively Remember too that PROCstep must have a step parameter of O to 50 The procedures are explained in table 2 I ve not used the standard Acorn PROC oscli routine so users of Basic 1 can t access these commands All AIV owners will have Basic 4 at least so the PROCoscli is replaced with OSCLI Taking control One of the most valuable computing lan guages is Logo and the most widespread version follow the LCSI standard hence the dialect selected in this next section is the Logotron version of Logo One conce
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