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
2
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
27779-24
?(~'~~~~~~
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.
