CA2076385C

CA2076385C - Process for recording and/or reproducing digital data on a record carrier

Info

Publication number: CA2076385C
Application number: CA002076385A
Authority: CA
Inventors: Ernst F. Schroder
Original assignee: Deutsche Thomson Brandt GmbH
Current assignee: Deutsche Thomson Brandt GmbH
Priority date: 1990-03-12
Filing date: 1991-03-02
Publication date: 1999-08-31
Anticipated expiration: 2011-03-02
Also published as: EP0573413B1; JP3986552B2; HU216451B; WO1991014265A1; EP0573413A1; FI924086A0; JPH05505275A; AU639762B2; ES2069282T3; HUT64430A; ATE117120T1; JP2007242234A; HK50496A; DE4007814A1; CA2076385A1; JP4543399B2; FI111108B; JP2010182418A; FI924086A7; AU7345091A

Abstract

In conventional recording processes, the digital data are recorded continuously from the beginning to the end of the track of the recording medium at a net data rate which is fixed in each case for the entire recording. The aim of the invention is to record and/or scan data on a recording medium with optional reading and writing access. Continuous recording of digital data is replaced by burstwise recording.
As a result of the burstwise recording of the data, each burst forms a cluster on the record carrier. The data are preferably recorded in CD standard recording format at a data rate of 1.411 Mbits per second. Recording and reproducing of data on a re-recordable contactlessly scannable record carrier, for example a magneto-optical disk (MOD).

Description

2t17~~~::~
t,'cr<t7 /7 9265 -- 7 - PCT/EP91/00389 process for recording and/or reproducing digital data on a record carrier (recordi_ng medium) Contactlessly scannable rotating record carriers (recording media) srach as a compact disk (CD) or magneto-ol:~tical disk (MOD) are suitable for storing digital data, l~reterably digital audio or video data, in large quantities.
T1-:.ese record carriers have, preferably, a spiral-shaped (I~el ic-~al) track. During the recording or playback olneration, the record carrier rotates i.n such a way that the track passes by a radially adju:~table scanning recording unit or scanning playback unit (laser', with a constant path vc~lc~cvi t.y (:standard For CD: l..?, rn/s) . A CLV (constant linear velocity) system in the recording or playback device ensures that: the constant path velocity is maintained.
With recording techniques used up until. now, the digital data are re<~orded continuously from the start of the track to the end of the track on the record carrier, using a nc-~t data rate estab-Lished, respectively, for the entire recording. This has the di:>advantage that for recording clat.a c.~n a record carrier, the corresponding data must also he continu<:~usl.y made available (this cyan be realized through ma:;ter tapes) . As this is not <~lways possible for the large memory capacity c>f ~~uch record carriers, the individual rercording of data is limited.
With standard audio recording in the CD format, the data rate is 1.4112 Mbit./s (= 16 bit (per scanning value) 99.7. kHz (~,tandard scanning frequency for CD) * 2 (for ~~~fi~85 stereo) . With a net data rata of such a 1«rge size (net data rate is the data rate whj.ch :ls needed to store, transmit, etc., far example) one sE~conc~ of sound information or one second of picture informeit ion) , playback t imes of about 60 min can be ~~chieved per record carrier. To lengthen the recording time and hence the playberck time, while keeping the same scanning frequency and recording in sterec;, there are data reduction processes known which do not record all 16 bits per scanning value at the aut;put of the analog-to-digital converter. For example, rdIC (near :instantaneous companding), MSC ( muJ.t i-adapt ive specs: ral audio coding! , DPCM ( different cal pulse-code modulation), ~~DPCM (adaptive differential pulse-code modulat ion ) or delt<~ modulat icon are t o be ment coned in this context; th'=se techniques allow data reduced sound recordings without severE~ loss of cxuality when compared to standard CD recordings, cahereby the playing time is extended to four hours per record carrier.
It is the obje<a of the inventi.c~n to guarantee, with opt iona7_ reading and wrii: ing access, recording and/or scanning c'.0 of data on a record carr:ler.
According to one aspect, the prHSent invention provide~~ a method of recording burins of digital data onto a rotating recording medium having a helical. data track moving at a fi~;ed linear rate with respect to a nead/write unit com-prising the steps of: temporarily storing said data bursts and reducing the data rate o:E said bursts dur__ng said storage;
recording said bursts as Clusters at spaccad locations around said tr~rck while leaving pauses between said clusters;
utilizing said pauses to relocate said read/write head before X30 recording the next burst .
According to aeother aspect, thfa present invention provider a record for storing and playing digital data representative of an analog signal digitized at a first data rate comprising: a helical data track, said data track including a plurality of data clusters, each of said data 27779-2~~

2a clusters being composed of a plurality of frames and each of said cluster representing a xnzrst of data having a data rate lower than said first data rate, at least one frame of each cluster having a code for ident ifyi.ng the cluster; and a plurality of pauses betws~en raid r_7.usters, said pauses providing operat::~on time for a recording/playback unit useful with said record.
Accorda ng to ys~t another aspect , the present invention provides a system t=or recording a digital representation of an analog ~~ignal onto a recording medium comprising: mean; for receiving saj_d analog signal and converting said analog signa~_ into a first digital signal having a first data rate; means f or compressing said first digital signal into a second digital signal having second data rate lower than ;raid fir:~t data rage; storage means for temporarily storl_ng said second digital signal; means for controlling said storage means and for dividing said second digital signal into a plural:~ty of bursts separated by a plurality of pauses; and meats for providjng said bursts and pauses to said recording med:lc_rm.
In principle, t:he c~onvent:ional continuous recording of digital data is replaced by a brarst-wise recording whereby each burst of data is, internally, continraously recorded.
Through using the burst-wise recording of data, each burst preferably forms a cluster on the record carrier. One burst of data means a fixed quantj_ty of dat<~, for example, one or more bits. A cluster. is under;~tooc~ as a fraction of a track which essent is~l ly cont<3lns one burst of data . A recording ?(~'~~~~~~
1x091/19265 - 3 - PCT/EP91/00389 with such clusters is hereinafter referred t~> as "cluster recording."
With this recording technique it is of no importance whether the data rate of the data to be recorded, in marticular sound data, wa s reduce<7 by means ~~f one or various data reductian methods.
With the help of the "cluster recording°' described below it i;s possible, inter alia, to perform the following m,~des of operatian:
1. Data recording with optional read:iog and writing arres;~ to data) also with differing net data rates.
2. .4 long p7 ay ( > 7. h) saund rE~cordin~t by means of a sound data reductic»~ technique such as MSC.

3. .4n extremely Lang play (up t:o 89 hl speech recording.
The d~~ta are preferably recorded like i.ta the CD
:standard r~,cording formats using the unchanged scanning ~~peed of 1.2 m/s arid the scanning frequency «f 94.1 kHz and, therefore, the standard CD data rate of 1.91'°~ Mhit/s, so that: no modifications are necessary to the C.I~V system and t: he equali~aer circuits of conventional recording and playback units.
Consequently, a recording of 1..411 Mbit on the record carrier which, far example, have been data reduced by means of the MSC technique, contains not information for just one second of wound recording like with the CD standard but, rather, informatiorA for approximately four seconds.
For t:!zis it is advantageous to provide the data to be recorded with an errar protectian code such as, for example, t:he cross interleaved Reed Solomon code (CIRf;), to ~Q~~~
U'~:~97 /1 4265 - 4 -- PCT/EP91/00389 interleave them pri«r to recording and, using a channel r-c~cle, f or example, an EFM (E:ight:--to-fourteen modulation) cede, to record tlern on the record carrier, whereby through t 1-~o EFh1 rode, the data are =otructured in EFM frames. Each fF'M frame r~referabl~,~ Contains 2~1 Bytes of wanted data.
It is advantageous if t:he track of the record carrier i:=, spiral-shaped and preformatted with unambiguous position da:~ta, preferably by means of the ATIP method. Thereby, each it>r~rst of data and hence each cluster on the record carrier Ice individually accessed in order t:o, far example, dc:~lete, rewrite or read, etc. the corn°esponding data. Such a data recording with optional readinc3 and writing access l~~~s great advantages, especially for computers. An individc.ial recordin~7 of, for example, sound data, is first m~:~de possible throu<7h this.
It: is advantageous to :~o dvimension the length of a .Luster such that it: corresponds to a whole number multiple ~>f an A'PIP block an~7 hence, the whole number multiple of an F;F'M frame. Consequently) the ur~ambi.guous allocation of an A~hTP blor_k and an F:f:M frame to a cluster is determined, thereby en~curing, above all; the unambiguous addressability c>f a cluster.
To improve an error-free recording, pricsr to writing a c~7_uster CL2 , the prior writt:en ~~luster C1~1 is preferably read again and in the case of a defective recording of e~iuster CL7., recorded anew, and t:he defective cluster marked i n order t:o avoid a repetition .anc9 a 1?layback. of the defective cluster upon playing back the record carrier.
In the following the invention is more closely e~;plained by means of an ex<~rnple illustrated in the drawing.

20'~~~~5 Vc'nl /l ~l?65 _. 5 __ PCT/EP91-/00389 Fig. 1 shows a block circa-it for recording a sound wlmnrmr I w i th MSc' ct<r ~:a redact.rion whiclu i s real i zed in a rt:~cording device.
After filterincl out the analog signal by means of a low t-,;-ass 1 and scanning by rnean;> of a 16-hit analog-to-digital converter c., scanning irnpul;:es each of 16 bits are available at the output of said converter ready for further processing. These scanning values - always arranged into 1ol-ocks - are subjected to a Fourier transformation in a >iaecial arithmetic: ~rnit 3. The result: is a set of 1029 ~~toec:tral coefficients f_or e<~ch block, wheret:~5 said set could also be or~t.ained, f~~r examp:Le, using ~3 digit:al spectral a~ralyzer normally u~~ed i.n measurement i:ethnology. The rate and phase values arc' now rnu:Lti.ple adaptive-cc,ded in an MSC
codes 4 , i . a . signi f ir_ant coef f ici.ent;s are l:~resented and t ransm:i t:Ced with many bits (up to 19) , less ;significant bits w,_th only a few bits. Very small insignificant coefficients are set to zero and not transmitted. The "tp is saved" in s~urh a case are added to other significant coefficients which are then correspondingly precisely trarnsmitt:ed.
After the MSC data reduction, the digital data leave t:he codes ~I wi th 308 .7 kHz and are f_ed to a l~aral7-el-to-serial c<>m%erter 5, the output of wtoi~~h is connected to the rl;~ta input of an i.ntermedia~~e memory E~. Whi3e the read-in c:lc>ck frequency of the inteomediate memory ie, 308700 Hz, the read--out frequency is 1.911:? MHz. A 7/32 frE~quency divider '7 converts tlue 1.9112 MHz clock frequency to 308.7 kHz.
The intermediate memor~~ is contr~o:led by a control unit 8 wloich infer alia compares the current position date 19 on the record carrier 11 with 'the desired position date. The int:ermediat:e memory only siclnals, via the sictnalling line 1:3, "Data Ready" when at least as much data as is provided fc:>r the set: desired burst i;s stored in tyre intermediate Wy91 /7 =1265 - 6 - PCT/EP91/00389 mcm<orv f~. If the rtec<>rding unit has reached i is desired yco:~ i t ion) then read ov.~t of the memory i.a acti vated via "Output Control" 12 and the corresponding burst of data is road out: from the intermediate memory using the CD standard recording data rate of 1..4112 Mbit per second, provided with a CIRC error code prwotectior~ (cross interleaved Reed Solomon code) in a Reed Solcpmon code~r 9 and subjected to interleaving (code :~preadincl) . An interleaving memory (not illustrated) is disloosed in the codes 9 for the interleaving. The whronologi.cal progression of the processing and recording of digital data is shown by a graphical representation in Fig.. 1.
As a contactle~~sly scannable rc>tat.ing record carrier 71, s~ir_h as the MnD, can be burdened v.~ith various physical defects, which can never be entirely avoided during production of the dish, the aud=io signals to be recorded are r~:~ded according to this special coding procedure. The data c<:~ded in the Reed S~~lomon codes 9 are subjected to an EFM
m«dulation (eight-t~~-fourteen modulation) in a modulator 10 and recorded on the MOD With the help c>f this line code, k~lnerehy the data are structured by the EFrI modulation into L:I~'M frames. This is also the format used on the compact a:~l;.
The recording is organized so th<rt: 29 bytes of wanted data (= 6 stereo scanning values each of 16 bits) are recorded in one EFM frame. As a result: of the interleaving, tine 29 bytes of dat<~ in one frame do not belong to neighboring scannin!1 values of the input wanted data. The data belonging t:o ac jacent :scanning v<~lues are distributed over ar~pro~,:imately 110 successive frames. This improves the error protercti.on.

H~'co)t/192~>'.~ __ ~ _ PCT/FP97./00389 The scanning or reproduction of data on the record c~arr i c:r i ~ carr.i.ecl «u t. , i n pri maple, reciprocal. t;o the recording.
The magneto-optical di:~k (MOD) 11 used mere as a cwnt.aci:les<~ly scannable rotating record carrier comprises a preformatted helical track which con tams data for c~haracteri::ing an al,~solute position and for wontroling the :;c~anni.ng unit. The pre format:ti.ng is ~~arried out with the A't'IP (abso:lute time in pre-clroove) method. F'or this, the toack is modulated horizont~~lly and with a frequency (?2.05 kHz;i proportional to the audio scannirng frequency.
'Plus frequency also serves Eor synchronizing a CLV servo in t:.he recording unit and/or playback unit. This frequency is, fcar its part, i.s phase-modulated in a biphasE~ format with t.l~e ATIP data. Tlue data rate which can be achieved through tlhis is relatively low but is sufficient for recording all~sc>lute position data in t'he format described above.
ATIP i.nformat.ion can b~e constantly read and output via aignal line 7.9 to the contr~~l unit 8 during t:he writing and reading of data on t:he record carrier. With the MOD this is realized in that ATIP information is read by means of the read/write unit (laser) and can be evaluated via the Cracking unit whi.clu also operates during reacting and writ inch.
The time segment on the storage medium containing such ATIP information is called the ATIP block in the following.
The format on t:he ~tOD is so arranged that during an ATIP
block, 98 EFM frames are recorded or read.
Therefore, yet unwritten locations of tine preformatted track on a record carrier like the one described above can be accurately located with the help of ATIP. The accuracy for t:hi s i s given L.y the number of EFM frame: ) in this case ~~r~
td091/7~3265 -- 8 - PCT/EP91/00389 w:i th an accuracy of 98 frames. 1~~ith an MOD «f the described format and a scanning speed of 1.2 m/s (as wi-th a CD), an Iv;I~M frame has a length c>f 136.05 microsecond:; and hence, an A'~l P block 13. 3 cosec. or 1 /'75 ser_.
A search procedure for to a certain ATI1~ (n) block is always performed ire that the preceding A'rIP n-1) block is read. If ~~his block is dec~~ded, it is klloWn that the desired black folk>ws immediately and can now be read or written.
The s~~arct~ procedure runs as follows:
1 . ~~eading the current ATIP, 2. deciding whether now waiting for up to one revi~l.~-it.ion is auf f ic:i ent: ar a jumy is necessary, 3. jump command from the mechanical side) 4. reading ATIP at (possibly coincidental) target, 5. deciding whether new track jumping i-s necessary for c~~rrection or only waiting far up to one revolution is ne~~essary, 6. reading ATIP until ATIP (n-1).
The d~asired rec_ordi ng is carried out i n that the digital data to be recorded, as mentiond above, are <3:;sc~rnbl ed in an int erme<liate memory 6 and output from this in bursts with the standard recording data rate for CD, i.e.

7.917.2 Mbit/s. Eac:~h burst of data in the intermediate memory is continuously recorded on the recor~3 carrier in a respectively allocated cluster with a fixed number (each 98) of ATIP bl~~cks and EFM frames. After this there is time to repositian correspc>nding to the downgraded net data rate.
if the intermediate memory is filled up again, the writing unit (laser optic:> and magnetic head) should again just arrive at or be ju;t in front of the end of the cluster written last. In order to be able achieve this, it is necessary that t:he number of frames per cluster is greater 2~~~~~~;'~
6~ci<) 1/7_ 92.65 _. g __ PCT/EP91/00389 than or eciual to t:h~e product. of reduction factor K and n~3xirnum number of frames per revolution (wit:h a CD approx.
21:20 at glue outsidei. With the MSC data reduction, the re~ducti«n factor h ~s 0.25 and the number of frames per cluster shc:~uld, therefore, be at least: a b:it larger than 555.
Owing to the unambiguous acidressab:ili.ty via ATIP, the lc~ngt.h of a cluster is a whole number multiple of the ATIP
7 c:rngth.
If thE~ recording stops at any random point, then the CIRC codi.n~~ part, because of the code spreading (interleaving), conr_ains data in the interleaving memory, <w~nt.ained in the Ref~d Solomon coder 9,, which belong to those already recorded. In this case the coding part can be halted and then sta~~ted again upon writ:ing the next cluster, thereby writing tlae remaining d;jta into the start of the nest cluster.
This is not always easy to put into practice because >t:opping the hardware is not: always poi>sible immediately and t~ecause there is a danger of: an imprer_ise linking of the d<-ita .
Therefore, a current c7_ustnr is not filled completely with wanted data but instead, it the ~~oding c}f the wanted cl~~ta, according to the interleaving length, is terminated before that and they, at: t.hE: end c>f the cluster the interleaving memory is just emptied.
Besides the consequences arising f-rom the interleaving it. should be taken into account that at: the start of the recording procedure for one cluster, the scanning unit or t:he read/write unit is switched over from read to write.
lie>wever) this scanning unit (Laser) c<~nnc>t always perform 2a'~~ ~~~~
4~'cn97 / 1 9265 - 10 -- PCT/EP91/00389 this very rapidly arid accuratel~,~. Therefore, at the start of a cluster, some data is frequently lost. It is for this reason that some dummy (empt:y) data is written at the start of a cluster, in this case 7. to 3 EFM frames.
In order to keep small the loss of: dummy data at the start and, through emptying the interleaving memory, at the end, which appears in every clu:~t.er, <~ clust.er is, tlrerefe>re, not: necessarily f;ept as sHoirt as possible. Owing to the necessary organization of a directory for the recorded cj~~ta and the i ntrinsic flexibili ty c~f the record carrier, winich of course should not be=_ eliminated through r.l~.~ster recording, the lengl~h of_ a cluster iv also not arbitraril~~ long.
'l.'he fol7.owing cluster length lc~ is defined here for tine MOD 13 with cluster recording:
7« - 1176 EFM frames - 12 ~3TIP blork:~ - O.lf, sec.
The di.stribut:ion within a ~clustea- is as follows:
Number c>f f:FM framer Content 7 link frame 2 run-in 1029 data 1.11 interleaving 2 run-out 1 1 ink f r~~me 30 unused This design means that 29696 bit;5 of- wanted data are recorded in one cluster, actually taking the space of 28229 bits.. The loss in storage capacity is 1/8 ---- 12.5 per Cent.

~,'c791 /1 4265 -- 1:1 - PCT/EP91/00389 A further consequence of this sper_ial. sf lect:ion :;poc i f i ed above i :~ t ha t: the c: lock frequency c~f the reduced w.irrted data is io a simple ;ratio to the "normal CD" clock f reqrrency 1 /9 * (1-1; 81 - 7/32.
The gross data rate which may be recordod is reduced by cluster recording to 1/9 as desired, but only 7/32 of the standard d<jte rate is avail;~ble for the net hate owing to the 7/8 loss.
Therevore, the net d<~t~a rate which can Ire achieved in t.l,ie above ease is:
7/32 * 1.9'l12 Mbit/s = 308.'7 kHz/sec.
This corresponds to specifying a quanti::ation with 3.5 bit/sarnple, a rate whicln is very realist-do when using m~~~dern dat:a reduc~t.ion techniques such as MSC being used here. Owing t:c~ t: tie simple dividing ratio of 7/32, a simple syncliz-oniz~jtion crf external, data-reduced sources with the record caroier is also possible with t:lie described design.
To summarize, cluster recorc9ing means, ~:herefore, that t: he wanted data is not rer_orded in a c:ontinucrus sequence of 7350 EFM frames per second each with 29 usab',~e bytes like with the normal Cn format. Instead, t~lie recording is carried out in clusters which in fact consist: of a cont::i.nuous sequence of a certain number of EI'M frames, but t hW. hetwe~~n L1e mlmt:ers the recording is n<ot CUntsinuous.
A result of this i:~ that. each cluster can be optionally accessed far reading and, in particular, als« for writing wit=hoot the information recorded in the precF~ding or following ~~lusters being disturbed.

~~~~ s ~~~()97./19265 -- 12 - PCTlEP9~/00389 For olntiona.l writing access to a cluster, no special uma:~carc~ irs necessary for the rapid running-ul> and running-ci:>wn of tl:F~ laser because of the suff:icientl~~ long gaps.
After writing a cluster there is a pausE~ which is used t.« position the start of the next cluster. 1n order to find t le start of the next cluster, the ATII' bloc)':s at the end of t.l~e next cluster are decoded. It is possiblE~, therefore, to position it: so that the ent=ire )=final cluster is read once again before the one directly next is written again. This a~ilows recording errors to be established and then break off tl~e recording procedure completely in the care of too many errors or at least give a warning to the user.
Following up on the idea of error reroc~riition, error c~c~rrection is provided in addition. F'or thi:>, the data of t:he last cluster is maintained in the :intermediate memory.
There are t:wo conceivable strategies for error correction:
Firstly, it is rehosit:ioned to tlne start of t:he c~3nfe<~tive cluster and then 'the data for this are written or,r_e again. Directly after this follow tree data of the following cluster. However, time is u:~ed for the l:~c~sit:ionincl so tluat the pau:~e between two wri ting Cycles is l~c:~ssihly not large enough for positioning, c~c~rrection reading, repositic>ning and correction writin<t.
As a recording error can also be :Linked with a flaw on the record carrier, it is better, in the case of an error, t.~:~ rewrite the data from the defective clustE~r fief:o the following cluster and the actual.following data into the then following cluster. The defective cluster is then marked so t=hat it can be simply omitted (jumped over) upon 1-eadi.ng-oul~.

~0'~6~p ~,~c~97 /1 9265 -- 13 - PCT/EP91/00389 The rnarking i s r_arrp ed out in the direct ory UTOC (User T;jbl a of Content ) c~f the re~~ord carrier or i n a special cluster at the start and fi:riish of the current continuous cluster re~~ording. It is also possi.bl.e to s<~ mark (for e:~ampl.e, a different synchronization word) the following <vluster, r~awritten for r_orrection, so that wi_t:h thereby an error i.n the preceding cluster is indicated. This means, h~~wever, that upon playback, one clusi:er must: always be read c>ut i n advance .
Data recordings from computers on the b{~sis of an ~,y~erating system such as MS-DOS are carried out in blocks of 1024 bytes. If a cluster corresponding to tl~e above details i.s designee, then 24 blocks with 1024 wanted bytes, possibly with additional bits for error protection, can be recorded without any problem in one cluster with at least 1029 usable EFM frames. As the addressabili.ty is also provided, cluster recording is, t.laerefc>re) also suitable for data recording in a comps ter .
Owing to the loi.ece--by-piece recording for the duration of 0.16 sec. and the subsequent pause of 0.48 sec. until the rer_ording of the following cluster, a positioning strategy is provided becausEe it cannot be assumed that the laser is located, of all places, at the start of the next cluster after the pause ha:~ expired.
One possible strategy, to be exylained in the following, should make clear the logical course of events;
in practice though, a deviation from this is certainly possible.
The data supplied by the MSC coder 4 of the sound data reduction method with 308.7 kBit~/s are, as mentioned above, portioned in the intermediate r<iemory 6 or a dual buffer.
'The read-in clor_k frequency is 308700 tiz and the read-out tWo91/14265 -- 19 - PCT/EP91/00389 clor_k frequency is 1411200 Llz. The length of the two lmnf fer s i ~~ each 197568 bi is - 24696 bytes .
Writing of the first c7_uster is :~t:arted at ATIP (n) .
After writing 1143 EFM framE~s, the writing process is ccmr_luded. After the waiting tame of 0.98 sec. which now fcol7.ows thE~ dual buffer wil"_l signal "Data ready". A search l:~racedure is now perfarmed on the block at ATIP (n+12) . Far this, a ma~:imum of Lour tracks must be jumped over moving towards the inside. In addition, a waiting time of max. one revolution may become necessary. Now the ne~:t cluster can tae written and sa on.
Up to 900 msec. are available for the complete p<>sitionind. The positioning must be reliably completed w: thin t:hi~: time.
It can be assumed that a jump to the neh:t neighboring track on the inside can be performed with grEV~.at reliability.
Therefore, the fol7awing strategy is also pc>:,sible:
Writing of the first cluster is started at ATIP (n).
A:Fter writing 1143 EFM frames, the writing process is c,ancluded. Directly after 'this a jump by onc:~ track towards the inside is made and a se;3rch procedure according to A'fIP (n+12) instigated. This is repeated until the io~termediate memory 6 signals "Data ready". When A'TIP (n+121 is found again the writing proce<'lure for the :,,rc:~ncj cluster begi ns . Af t~er this wri ting pr~acedure has finished there is t:hen anat:her jump of one track towards the inside and again a search pr°ocedure for ATIP W +1?.) and so c:> n .
The a<9vantage wi th this strategy :i s that, the jumps will always be «nly by one track although the procedure must take WtWl/142E~5 -- 15 -- PCT/EP91/00389 ll.ace more frequently. The recording of the next cluster c;~n begi.n <jt the latest one revolution after "Data ready".
If after writing tine first cluster a search procedure fmr ATTP (n) ie~ run at first, i.e. after the start of the cluster just written, then the data just writ: ten can be read <~s a means of checking. An evaluation of thE-~ errors which O.~ve appear ed can instigate suitable measures, for example, w,~rning signals or display ~~f the error rate.
If upcm the control reading, errors which cannot be c~~~rrected are detected, then a cluster at ATI:P (n) recognized as defective can be rewritten at ATIP (n+12).
This is noted in a suitable manner in the UT(:~C (User Table of Contend so that the defective cluster at ATIP (n) can be omitted dul"lng playback. Tlhe intermediate mE>mory 6 is suitably cpnstructed, for e:Kample, as a cyclic triple dual braffer in order to he able to execute the writing repetition d~~sr_r ibed -i n the case of errors .
The method described above is not restr:i.cted to data-r~eduction of data and a certain data-reductic:~n technique such as the MSC used here. Likewise, a recording and r~eproductic~n with non-data-:reduced dato and/or with reduced data rates by means of other data-reduction l:er_hniques can l~~e carried out on a record .carrier.
One further possiblity of recording or rweproducing data would be tr> record on to the record carrier c:~r to read the data rate :reduced try means of MSC burst-wise with the help c~f tl-~e intermediate memory and then, after a r_ertain recording or playback time, to pause three t:i_mes as long.
Tn this ma~:~ner the record carrier can be fil:l_ed to 25 per c-~ent in on~~ run. If one comes to the end, one can jump back again to tl~e beginning during a 3/4 pause and fill or read a further :25 per cent of the disk in a second run and so on.

2~'~~~' h'~7~)l./7 9?.65 -- 16 -- PCT/EP91/00389 'This neces:>itates a difficu=Lt organ:izatic>n of the disk ~~ ~n t can I :: . Tl»~ rcwr~r<l <.varri er then cosata:i ns c.~ i ther one just ocprmal or one data--reduced program. 'rhe defined jump from the end to the start of the track is ~,~ritical.
One fundamentally different possibility independently 01= the solutions described ~~bove would be to reduce the scanning speed rorrespondinc~ to the reduction factor. If t.lne wavelength on the recorci carrier :remains the same, then w:i.th a reduction factor of 1/4 this would result automati.ca7.ly in a quarter of the recording data rate and a p-layi.ng tine four times as Long. However, ttue CLV system mist be swutchabl.e. Apart From that, the equalization cvircL~its, for the signals coming from the record carrier, c.~nly receive signals with one-quarter of the normal 1=req~.~ency and must, therefore. be switchable. A mixing of "normal" recordings and date-reduced recordings on one disk is then only possible if a rapid switchover c~f the CLV by floe factor of one-quarter o:r four respectively is possible.
'fhe invention can be applied equally tc> a recording and/«r pla~ihach of digital data on a magnetic~ tape with PCh1 .signals or a recording on a DAT (digital audio tape? in a DAT recorder . Tlue organizational str~.tcturP of a DAT
r~~c-ording cyan be established in an equivalent. manner to the nnsthod des<~ribed a>~~ove with only slight modif ications.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of recording bursts of digital data onto a rotating recording medium having a helical data track moving at a fixed linear rate with respect to a read/write unit comprising the steps of:
temporarily storing said data bursts and reducing the data rate of said bursts during said storage;
recording said bursts as clusters at spaced locations around said track while leaving pauses between said clusters;
utilizing said pauses to relocate said read/write head before recording the next burst.

2. The method of claim 1 wherein each of said clusters has a predetermined number of frames.

3. The method of claim 2 wherein at least one frame of each cluster is used to code the location of the cluster.

4. The method of claim 3 wherein at least one of the frames in each cluster is used to code the location of the next cluster.

5. The method of claim 3 wherein each of said clusters includes an error reduction code.

6. The method of claim 5 further including the steps of reading the last recorded cluster prior to recording the subsequent cluster onto said recording medium, and rerecording any cluster found to be defective.

7. A record for storing and playing digital data representative of an analog signal digitized at a first data rate comprising:
a helical data track, said data track including a plurality of data clusters, each of said data clusters being composed of a plurality of frames and each of said cluster representing a burst of data having a data rate lower than said first data rate, at least one frame of each cluster having a code for identifying the cluster; and a plurality of pauses between said clusters, said pauses providing operation time for a recording/playback unit useful with said record.

8. The record of claim 6 wherein at least one frame of each of said clusters includes a code for locating another cluster frame of said record.

9. A system for recording a digital representation of an analog signal onto a recording medium comprising:
means for receiving said analog signal and converting said analog signal into a first digital signal having a first data rate;

means for compressing said first digital signal into a second digital signal having second data rate lower than said first data rate;
storage means for temporarily storing said second digital signal;
means for controlling said storage means and for dividing said second digital signal into a plurality of bursts separated by a plurality of pauses; and means far providing said bursts and pause to said recording medium.

10. The system of claim 9 wherein said means for dividing includes means for dividing said second digital signal into a plurality of frames, and means for combining a preselected number of said frames into each of said bursts.