GB2260463A - Vision mixing simulator - Google Patents

Description

n - 0 " -)34 157 VIDEODISC AND VIDEODISC PLAYER, AND VISION MIXING

SIMULATOR USING THE SA1,1E This invention relates to the storage and replay of changing visual images using a videodisc, that is to say a so-called,laser disc", or a compact disc (CD), or the like, capable of storing visual images in such a way that selected frames of the images can be made available as desired relatively rapidly.

In such a videodisc it has been proposed to record several different sequences of images with the frames of the sequences interleaved. Thus if n video image sequences are interleaved on a frame by frame basis, when reading the disc the videodisc player selects just one in every 11 frames, so as to present sequentially the frames of just one sequence. The player skips the intervening n - 1 frames. This has the advantage that it is very easy to change from one sequence to another. This is achieved by the player skipping less than n - 1 frames on one occasion only. This then locates it on a frame from a different seauence. After that it continues to skip n - 1 frames until another change of sequence is reauired.

There are limits on the actual capability of the read head of the player to jump during the conventional frame blanking period of a video signal of broadcasting standard. For examle, the Phili:Ds 400 series laser disc players can jurrp plus or minus 50 two-.F, _Leld frames within this period. The junp is in f act achieved by flipping a mirror, and after the jump the main laser c arr iage has to "relax" or return to its centre position before another 50 frame jump can take place. Practical considerations in fact limit the on-zhe-fly instant jumps to 20 frames, because of this relaxing of the laser carriage.

Each secuence of frames may conveniently be termed a "universe", and thus the maxi= n=ber of universes that can be interleaved on a JLrame-by-frame basis is about 20, with the player plavi.ng one frame andthen skipping 19.

lle have aiDr)reciated that although pictures are relatively easy to handle to produce .,4erleaved seguences, by videotape (VT) editing or by optical film printing, the sound is a far greater problem if this is recorded along with the images. Because the videodisc player gets its sound from. exactly the same carrier signal as the pictures, the sound will be played with discontinuities wherever the laser head jumps francs. With the interleave described above these discontinuities occur once per frame period, which, for a 50 field per second picture, is 40ms, and this adds a high level of pulse noise to the sound which it is difficult to remove or mask. The pulse rate frequency itself is 25H2, or 30Hz for a U.S. standard player. Also the 40 m segments are too short for the VT edit to handle; separate sophisticated digital editing techniques would be needed.

In accordance with this invention in a first aspect we propose that the interleaving of frames comprises the interleaving of n blocks of j frames, where j is a number sufficiently greater than one such as to reduce the noise pulse rate in the audio channel to a point where it can adequately be disguised.

The blocks of frames way contain at least four frames in each block. Preferably j will be at least ten, and typically is around 20.

T1he use of a block size of the order of 20 frames has distinct advantages. On recording of the disc, it is not difficult for the relevant audio to be edited with the video, since 20 frame segments are large enough for a videotape editing facility to edit sound with pictures.

On playback a click every fourfifths of a second is less of a problem than 25 clicks a second. it should be possible to use a device such as those used to I'de-clickIl gramophone records to disguise these with little degradation of the final sound.

Interleaving blocks also has the effect of reducing the apparent errors if the videodisc player Ilmis-jurrps The invention also provides a videodisc having recorded thereon a plu- rality of sequences of francs with the sequences being interleaved, the interleaving comprising the interleaving of blocks each of a plurality of frames froin each sequence.

In. accordance with a f=ther asnect of the invention we provide an,=t.. eract,.ve video mixing simlato-r system comprising a videodisc having recorded thereon a plurality of video signals, such as the output of a plurality of television cameras, in a plurality of sequences in interleaved format, a videodisc player for replaying the recorded images such that one of the interleaved sequences is replayed at a tire, and manually operable means for changing the selected sequence being replayed, such as to simulate a cut from one camera to another.

one example of the use of such a system will now be briefly described with reference to the drawings, in Which:- Figure 1 is a diagram illustrating the sequence of frames on a videodisc and the manner in which the juirps are made; and Figure 2 is a detail illustrating a modification of the system in which certain frames are duplicated.

The example to be described is concerned with the simulation of a television control gallery which allows interactive training of directors, production assistants, vision mixers, and others. The system uses a Philips 400 series 12 inch videodisc player. The disc holds pictures from three can-eras together with a sound channel and allows trainees to cut between the camera outputs to produce an edited result.

The outputs of the three cameras are recorded in cyclically interleaved fashion with blocks of 20 frames from each camera being interleaved. Normally the camera outputs will be recorded on tape and the tapes edited to produce a recording with the interleaved blocks of frames. The interleaving is produced on a final tape which becomes the master from which the videodisc is pressed. When the trainee is steadily using the output of one camera, the player skins 40 frames at the end of each block so as to pick up again at the start of the next block from the same camera.

If the trainee indicates that a change of camera is required, the player instead may make a once-only jump of 20 frames or omit the jump altogether, depending on which of the other cameras is now reauj-red to be fed to the out:put. More generally, a jump of plus or minus 20 or plus or minus 40 way be used. It will be appreciated that the cut my be initiated at any point in the replay of a block, in whidh case a different number of frames may be jumped so as to nick un at the start of the next block f rom another camera, or ar- the corresponding point in the next block.

Figure 1 illustrates such a system. In this illustrative system only ten frames are shown as constituting each block so as to show the frames more clearly. The frames are shown at the top of the figure in their arrangement on the videodisc track. At (a) is illusr-rated the sequence of jumps when the output of camera 1 is being displayed continuously. The head reads the j (ten) frames from, camera 1 and then jumps (ri71)j frames, i.e. twenty frames, so as to pick up at the start of the next block of frames from camera 1.

At (b) and (c) are illustrated the sequences of jumps at the poinz Vnere the output of can-era 1 is changed to select the output of camera 3 or camera 2 respectively. In (b) there is one jump of ten frames instead of the usual twenty, and at (c) the jurrp reduces to a j= of zero frames, i. e. no jump at all.

The recorded frames in fact are each split. The greater part of the frame area comprises the output of the designated camera, bur- a small part of the frame, in fact the bottom of the frame, is used to show the outputs of all three cameras including the two "non-selected" can-eras. In this way a single CRT display can be used to display the. outputs of all three cameras to the trainee.

This also means that the bottom portion of each displayed frame is the same. This helps to make the jump less visible, for the following reason. In fact there remains a small problem caused'by the exac.= timing of the jum that takes place. Although in theory the jump should all take place within field blandking, in practice it is carried out a little before the field blanking so that the read head will be able to read a 24 bit code in the next blanking period. This read is needed to confirm that the jump has been successful. Therefore t-he read head leaves the "departure" field before it has completely finished and lands before the intended "arrival" field has started. This shows as a small portion of the field before the intended arrival field, visible nuneentarily at the bottom of the franc. If the bottom part of the frame of each of the sequences (universes) is the same, this will be barely noticeable.

An alternative way of overcoming this problem is to record an addLz-onal frame at the start of each block, this frame being the n 1 11 i same as the last frame of the previous block from that universe. This means that each block is now one frame longer than previously, so a 20 frame block now becomes a 21 frame block. The read head then junps from near the end of the last frame of one block to the corresponding point near the end of the first frame of the next block of the same universe, as illustrated in Fi aur e 2. The actual,,landing,, f ield will thus be identical to the "take-off 11 field and so will minimise visible discontinuity. Figure 2 shows part of the secuence of francs j'-rm cameras 1, 2 and 3. Any remaining portion of the actual landing field that is displayed is from the co=ew-- camera and not f= camera 3 instead, as would happen if the duolicare field were noz mresent. As it is iTmrac-- ical to duzlicar-e a sinale field the whole of the relevant frame (both fields) is duplicated inszead. This has the added benefit of removing cu"sconzmu-ir-ies caused by pre_rnature]Lrp=g from the f -sz f i eld of the take-oc frame. The continuous r)lav almrit,-n can now be wrizten as play j frames; jurrp C (n-1) j+n]

A=-jroo:-iaze software to co=ol the videodlisc r)laver can readily be writ-zen by =hose skillied in the a---r-. The user uses a keyboax-d to ix7,-e=ar)z a conzrol loop so as tO ir.-:erc= be--we--n urLiverses.

Inst-ead of -ELe--c-J-ig -rhe ou=uz to videozaD--, the svsze-m can simlv keer) a re-cord of the cuts made by -trie trainee. In a ren, cv mode t. he tra-,ne-- Is can then be reproduced e-xac--!y for r)u---cses.

nav be possible zo inco=ra-ce dixital s-zecial effec-s tO mrovide: a zoom ez--r-e= =or e--.amle, or'the use of add.---Jor-al still.,_rames. otner surwrT:.LncT material may be recorded such as capr-lons, oror-ocra-ohs, floor plans, the control callery talk-back, sc_-ZS' end so or.. us--,-'.g advanced:-,rage processing zec:,zncues it iray be oossible -cc allow zhe tr =c-- to re-Dos=ion cameras on the OM with -n-ie system s=latincr the view of tkie ser- fr that =-m--ra posizion. Camera moves my similarly be s.,:..-,-ilated.

The svsze-,r, =--i, of course, be ada-or---a for the or svszens z:,=. described.

Reference should also be made to British patent application number GB-A-2-11-9889 from which the present application is divided.

1 =A MIS 11 An i=erac-r-ive video mixing sinulator svsze-m c=rising a videodisc having recorded thereon a lplurality of video sim-ials in a p!=. all i-cy of sequences in interleaved -iE-CD-rreL., a vide-disc plaver for emiav:Ln.a the recorded iraces such thar- one c- the interleaved se=Lle-,lces J; replayed az a time, and manually ope-rable na.= for changing the selecr-ed sequence being replayed, such as to simalaze a cat f= one camera -CO another.

2. A- svszen., acco=-dirz zo claim 1, in iric,i zhe videodi, sc has recorci.:=-d thereon zhe of a r)lural--=,7 of television cameras.

3. TA- svsze--i acco,-dL-ig zo claim 1 or 2, Ln wiL, dh zh.e:LTire=, leaveci f blod Zor.Maz comr-ises zhe inzerleaving o- ks, each of a plurality of from each 4. A svsze--., ac=rding zo claim 3, in whidh the JErame or ie, a o-M eadi block renea-,-s the las.= frartree or d of the ur--ce=a- block in -r-he same sequence.

= c ai=.s 1 to 4, in wil:,_d.-, in nc)=-,a-", 5. X'% ZO a-TIV 0.1.

the r)laver reads the -a.

s one sequence only and over zhe Sewpences, W.1a 2--IC,i=,g means, -esDons2.ve zo -dhe,r.!-nual ly-operabl, c n-cans for changing the SeaLlence, WhicIrl M--W..5 dwmaes the J= S-ize =or one Dunp so as to read a diff-erenz one of the sec:rjences.

6. _;--= Z-u.. - W=2.Ve VICCO SYSZani su sze-=--.a-lly as Ii- a b u 1