CA1228417A - System for playing back a programme recorded on a disc-shaped record carrier - Google Patents
System for playing back a programme recorded on a disc-shaped record carrierInfo
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- CA1228417A CA1228417A CA000375053A CA375053A CA1228417A CA 1228417 A CA1228417 A CA 1228417A CA 000375053 A CA000375053 A CA 000375053A CA 375053 A CA375053 A CA 375053A CA 1228417 A CA1228417 A CA 1228417A
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- Television Signal Processing For Recording (AREA)
Abstract
ABSTRACT:
Prerecorded video discs will generally be provided with a programme which has originally been recorded on film,which programme is transformed into a television signal by scanning the film frames. Owing to the difference between the standards for film and television employed in the United States consecutive film frames always result in sets of un-equal numbers of fields on the record carrier. Pre-ferably an indication signal is added to each set of fields on the record carrier. The read apparatus comprises detection means for detecting said indi-cation signal. This signal is used to ensure that in the still-picture mode, during which the same two fields on a track circumference of the record carrier are repeatedly read, two fields are read which belong to the same set and consequently stem from the same film frame,
Prerecorded video discs will generally be provided with a programme which has originally been recorded on film,which programme is transformed into a television signal by scanning the film frames. Owing to the difference between the standards for film and television employed in the United States consecutive film frames always result in sets of un-equal numbers of fields on the record carrier. Pre-ferably an indication signal is added to each set of fields on the record carrier. The read apparatus comprises detection means for detecting said indi-cation signal. This signal is used to ensure that in the still-picture mode, during which the same two fields on a track circumference of the record carrier are repeatedly read, two fields are read which belong to the same set and consequently stem from the same film frame,
Description
PIN. ~717.
This is a divisional of Canadian patent application Serial No. 298,552 filed March 9, 1978.
The invention relates to system for playing back a programmer recorded on a disc-shaped record car-nor, which system comprises a read apparatus for scanning the record carrier, said record carrier being provided with a spiral information track in which the programmer is recorded as a television signal in a sequence of two fields per turn of the track, and con-secutive scenes of the programmer on the record car-nor being constituted by consecutive sets of fields, each set comprising either two or three fields, in accordance with a regularly repeated pattern of sets and the read apparatus being provided with control means for realizing a still-picture mode, in which mode the same two consecutive fields are repeatedly read by the repeated scanning of the same turn of the track.
Currently disc-shaped record carriers come mend much interest as a storage-medium for video in-formation. This applies in particular to disc-shaped record carriers on which this video information is recorded in optically coded form. For reading these record carriers a read apparatus is employed which uses an optical scanning system. With the aid of a PUN. 8717.
beam of radiation a scanning spot is projected onto the record carrier and information which is contained in this radiation beam after interaction with the record carrier is detected and converted into a tote-vision signal which is suitable for reproduction vice standard television receiver. Control systems, which may inter aria comprise deflection means inter-posed in the radiation beam, ensure that the scanning spot always coincides with the spiral information track on the record carrier. Such read apparatus, in particular the control system used therein, is inter aria described in US. Patent Specification No.
3,854,015 which issued to US. Phillips Corporation on December 10, 1974.
The major advantage of using an optical coding on the record carrier in conjunction with an optical scanning system is that scanning is entirely con tactless, so that the risk of damage to the record carrier is minimized irrespective of movements of the scanning spot over the record carrier. During read-out this inter alias provides the possibility of using a still-picture mode, which possibility is comprehensively described in the above Patent Specific cation. In this still-picture mode the scanning spot is moved back radially by one track pitch after every revolution of the record carrier with -the aid of the deflection means, so that continually the same turn of '7 PIN. 8717.
the spiral track is scanned. As exactly -two fields are recorded in one turn of the track, which fields together constitute the interlaced television image, one specific picture of the recorded television signal is reproduced continuously in the still-picture mode.
Said record carriers are primarily intend-Ed to be provided with a programmer by the factor and thus to be made available to the consumer as prerecorded record carriers. The most likely pro-Grimm material for this type of prerecorded record carriers is constituted by film material because -this is available in large slot and in a wide repertory.
If a film programmer is to be used for the manufacture of record carriers destined for the American market, a complication results from the difference between the standards for the reproduction of film images and those for the reproduction of television pie-lures.
The standard mainly used for film inter a_ implies that 24 film frames per second are no-corded and reproduced. In order to convert such a film into a video signal which is suitable for no-cording on said disc-shaped record carriers, each film frame is scanned in accordance with a pattern of interlaced fields. However, in accordance with the United States television standard, 30 pictures PUN. 8717.
per second must be reproduced, so that it is not posy sidle to transform one film frame into one television picture because then the playback speed of the record-Ed programmer would then not be correct. The necessary adaptation can be obtained in known manner by program-mint the film scanner so that consecutive film frames are alternately converted into a set of two fields and a set of three fields. This means that two film frames are converted into five fields or four film frames into 10 fields or 5 television pictures, which correspond to a 24/30 conversion from the film standard into the television standard. In order to obtain this transformation it is not necessary per so to convert consecutive film frames into alternate sets of two and three fields. It is also possible to use a different sequential pattern. For example as an alternative four consecutive film frames may be converted into consecutive sets of two, three, three and two fields.
Any pattern with a period which is so short as not to be observed by the human eye may in principle be used.
If a read apparatus for disc-shaped record carriers is operated in the still-picture mode it is found that the reproduction quality is not always satisfactory when record carriers are used on which a television programmer is recorded which is obtained in the manner described above. Often the television picture which is reproduced in the still-picture '7 PUN. 8717.
mode exhibits blurring and in the case of certain programmer it is even completely unacceptable.
It is an object of the invention to imp prove this situation and the invention is kirk-terraced in that to at least one of the fields which together constitute a pair of consecutive sets of television fields on the record carrier an indication signal is added and that the read Papa-fetus is provided with detection means for detect-in this indication signal and with selection means which are coupled to said detection means and which co-operate with the control means, which selection means as a function of the detected indication sign net in conjunction with the control means, it adapted to select the two fields to be reproduced in the still-picture mode in such a way that the two fields reproduced belong to the same set of fields.
The invention is based on the recognition that in the still-picture mode of the known read apparatus two interlaced fields may be reproduced which stem from two consecutive film frames. As the scenes recorded in two consecutive film frames generally differs slightly, in particular in the case of fast-moving scenes in the recorded pro-Grimm, the fields stemming from these individual film frames will also differ. If these fields are I Lo PUN. ~717.
are then combined into a television image by inter-lacing, a blurred picture results.
This is largely avoided by the steps in accordance with the invention in that first of all during the recording of the video signal on the no-cord carrier an indication signal is added to each pair of consecutive sets of fields. By providing the read apparatus with detection means for detect-in this indication signal it is achieved that lo information is available in respect of the field which is being read at that instant during the still-picture mode. This information can be employed for programming the control means via selection means controlled by this indication signal in such a way that, in this mode, the two fields reproduced always stem from the same film frame.
Preferably an indication signal is added to each set of fields on the record carrier, be-cause in that case the selection means can be very simple.
The added indication signal may also serve as an address signal, ye. it may contain such a code that the indication signal after detection not only has the above mentioned function in the still-picture mode, but that after decoding of the code which is contained in each individual indication signal, it also provides a frame number associated with I I
PUN. 8717.
each film frame which may, for example, be displayed on the television screen simultaneously with the reproduced television picture or via a separate disk play.
Embodiments of -the invention will now be described, by way of example, with reference to the accompanying drawings, in which Figs. 1 and 2 schematically represent the manner in which a film programmer is recorded on a disc-shaped record carrier, Fig. 3 schematically shows the read appear-tusk for such a disc-shaped record carrier.
Fig. 4 in tabulated form shows the possible locations for the indication signal in consecutive sets of fields.
Fig. 5 shows a form of the selection means which may be used in the read apparatus of Fig. 3, Fig. 6 shows the signals appearing there-in in the various scanning modes, and Fig. 7 schematically represents the scan-nine sequence of the sets of fields thus obtained.
Fig. 8, which is on the same sheet as Fig. 5, finally shows an alternative form of the selection means.
Fig. lo schematically shows how a programmer recorded on film is reproduced. Each of the film frames I through IV is consecutively reproduced for PUN. ~717~
1/24 of a second. If such a film programmer is to be converted into a television signal, it is necessary to ensure that, per second, this television signal sequentially represents the information content of 24 consecutive film frames, preferably in an as regular as possible manner. To obtain a television signal in accordance with United States standards, which signal contains 60 fields per second, a con-version is necessary of which a possibility is repro-sensed in Fig. lb.
Fig. lb schematically represents the repro-diction of a television signal which consists of 30 television pictures per second. Each television, as is known, consists of two interlaced fields. Within a time interval of 1/6 of a second in which 4 film frames (I through IV) are reproduced it is therefore necessary to reproduce 5 television pictures of 10 fields (1 through 10). In order -to achieve this the film frames are converted in known manner into a television signal, which changes from film frame to film frame, with aid of film scanning equipment.
The first film frame I is scanned in accordance wit two fields 1 + 2 resulting in a television picture So (Fig. to) consisting of these two interlaced fields 1 + 20 The second film frame II is first of all scanned in accordance with two fields 3 + 4, resulting in a television picture So consisting of PUN. 8717.
these two interlaced fields 3 + 4, but subsequently this film frame II is again scanned in accordance with a field 5. Thus, in the television signal this film frame II is ultimately represented by three fields 3, 4 and 5. The next film frame III again yields two fields 6 + 7, film frame IV three fields 8, 9 and 10, etc.
The Figure readily shows that in the time interval (1/6 of a second) which is necessary for reproducing 4 film frames exactly 10 fields are no-produced, or 5 television pictures. Owing to the alternate sets of two and three fields per film frame the sequence of the original scenes recorded on the film will be slightly disturbed during nor-met reproduction, but because it is disturbed with frequency of 12 Ho this is hardly perceptible to the human eye.
Instead of the conversion illustrated in Fig. 1 i-t is readily possible to select a conversion in accordance with the film frames I and IV each no-suit into two fields and the film frames II and III
each in three fields. Moreover, a pattern of sets may be chosen which is divided among more than four film frames, each pat-tern comprising an equal numb bier of sets of two and of three fields.
If during read out of a disc-shaped record carrier the still-picture mode is selected it is PUN. 8717.
found that in certain cases an unacceptable picture, in particular a slurred picture is produced. It is found that such a blurred picture in -the still-picture mode may be attributed to the selected con-version of film frames into television signals This is illustrated by means of Fig. 2 in combination with Fig. 1.
As previously stated, the video signal is recorded in a spiral track on the disc-shaped record carrier, each turn of the track comprising two fields. Fig. 2 shows such a spiral track T. This track is scanned by a rotation of the record carrier in the direction P, namely from the inside towards the outside in the example shown. Assuming that recording of field 1 begins on the radius R, the fields 1 through 10 will occupy the indicated track portions, i.e. the odd yields the track portions to the right of the radius R and -the even fields the track portions to the left of the opposite radius to R. A sequence of odd and an even field always con-statutes one track circumference, corresponding to one television picture Sly S2,...S5.
In the still-picture mode of the playback apparatus one turn of the track is scanned contain-usual in that the scanning spot is moved backwardly over a distance equal to the track pitch I 7 1 I . 6 . 77 of the spiral track upon each revolution of the no-cord carrier, said movement being referred to here-inciter as track jump. Obviously, such a track jump is noteffeeted at an arbitrary instant, but always during the vertical fly back of the reproduced lo-Louisiana signal, in order not to disturb the disk played picture. furthermore it its common practice for the track jump to coincide with the beginning of the odd fields by detection of the ~ertieal synchronizing signal, so that in the still-pieture mode pictures are repoured which always consist of an odd followed by an even field, i.e. eons-eutive pictures So, So, So eye. In the present example the track jump is therefore always effected at the location of the uninterrupted part of the diameter along R.
In the still picture mode the scanning spot for example follows the path indicated by the dashed line, so that the picture So consisting of the fields 1 and 2 is reproduced. This is found to be, an entirely correct picture. If in the still-picture mode the scanning spot follows the path in-dilated by the dashed-dot line, the picture So con-sitting of the fields 5 6 is reproduced. In Fig.
1 it can be seen that the two fields 5 and 6, which in interfaced form constitute said picture So, stem from two different film frames, namely the frames . - 12 I
14.6.77 ;
- II and III respectively. These two fields will cons-quaintly represent different scenes which in the still-picture mode are then alternately reproduced for 1/60 sea, resulting in an unacceptable picture.
The picture So, consisting of the fields 5 + 6 it therefore not suitable for reproduction in the still-picture mode. The same applies to the picture So, consisting of the fields 7 8, as can readily be seen in Fig. 1.
' In accordance with the invention indication signals are added to the recorded video signal in or-dyer to prevent these problems in the still-picture mode of the read apparatus. These indication signals are detected during read-out and together with the selection means, which are responsive to these in dilation signals, they ensure that in the still-picture mode only combinations of two fields which stem from the same film frame are reproduced.
To explain the operation of the system in accordance with the invention Fig. 3 schematically shows an embodiment of an optical read apparatus.
This read apparatus largely corresponds to that shown and comprehensively described in the said Patent Specification No. 1,429,882.
The disc-shaped record carrier 11 is driven in a rotary sense 13 about its center 12 and comprises a spiral information track T. The . 7 PIN 8717 . 7 7 optical scanning system comprises a radiation source 14 which produces a radiation beam 15. This radiation beam is focused to a scanning spot I via the semi-transparent mirror 16, the mirror 17 and the tense 18. After reflection the radiation beam is again incident on the mirror 17 and the semi-transparent mirror 16 by which it is partly reflected to a de-Hector Z0. This detector first of all serves to de-toot the video information contained in the radiation bean and make Kit available at a terminal 21.
Moreover it is assumed that the radian lion beam which is incident on the detector 20 contains information relating to the radial post-lion of the scanning spot 19 relative to the inform motion tract, which results in a control signal at the terminal 22. Systems for obtaining this inform motion relating to the radial position of the scan-nine spot are known in a multitude of variants. As it is irrelevant for the present invention which system is used for this purpose, reference is mere-my made, by way of example, to the possibilities described in the said Patent Specification. The control signal which is available at the terminal 22 is applied to a drive means 27 via a control amplifier 25 and the switch 26~ which drive means can rotate the rotatable journal led (point 28) mirror 17 in the direction 33. Thus a closed con-7 14.6.77 trot system is obtained for controlling the radial position of the scanning spot 19, so that it is ensured that the scanning spot lo always coincides with the information track T.
in the still-picture mode of the read apt pyrites the scarLning spot lo should radially be move Ed back by one tragic pitch of the spiral track at every revolution of the record carrier 11. on or-don to achieve this the control loop of the radial tracking system is briefly rendered inoperative once per revolution of the record carrier, in that for example this loop is interrupted by the change-over of the switch 26. During this short time a signal source 32 then supplies a suitable control signal (jump signal) to the drive means 27 via the switch 26, so that the mirror 17 is rotated in such a way that the scanning spot 19 is rapidly moved by one track pitch in the radial direction.
Subsequently, the control loop is again closed by means of the switch 26, so that during the rest of the revolution of the record carrier the in-formation track is normally followed.
The control signal for the switch 26 and the signal source 32 is supplied by a selection Z5 circuit 31, which has two inputs which are connect-Ed to two separate detection circuits I and 30.
Both detection circuits receive *he television signal 14.6.77 weakly is taken from the terminal 21 of the detector 20 and which is decoded with the aid of a decoding device 23, from which signal they extract the Yen-tidal synchronizing signals (detector 29) and the indication signals B (detector 30~. The detection of the two signals jointly defines the instant in the stil].-picture mode at which the control loop of the radial tracking system is interrupted and the jump signal is applied to the dry means 27 of the mirror 177 in other words the instant at weakly -the track jump of the scanning spot is per-formed.
By a suitable choice of the position of the indication signal. within a set of fields on the record carrier in conjunction with a suitable design of the selection circuit, it is then posy sidle to ensure that in the still-picture mode always two fields are reproduced which stem from one end the same film frame. In respect of the pox session of the indication signal within the sets of fields on the disc in conjunction with the design of the selection circuit there are a number of posy sibilities. The most significant possibilities are schematically shown in Fig. 4 in the form of a table.
In Fig. 4 in the upper part of the table fields are indicated along a time axis t, showing ~;~2~17 PUN 871 7 11~.6.77 that the fields 1 and 2 stem from film frame I, fields 3, 4 and 5 from fill frame III, and fields 6 and 7 from fillrl frame III. In the rows 1 through 6 so-venal possibilities for the location of the indict-lion signal are given, which location is further specified in Callahan B. Column Z indicates at which instant the track jump occurs.
or the sake of clarity possibility 1 is considered first. As is indicated in the table by crosses an indication signal is added to the first field (r1) of each set (I, II, etc.) of fields, i.e. to the fields 1, 3, 6, etc. It is evident that tilts indication signal is included in the non-visible part of the television signal, i.e. in tile vertical planking period, nclmely after the vertical synchronizing signal. The selection circuit in the playbacli apparatus ma-y now be designed so that the control signal which causes the track jump in the still-picture mode is produced by the second Yen-tidal synchronizing signal (represented by I in calmly Z) after detection of the indication signal.
If the still-picture mode is switched on and sub-sequently the indication signal associated with field 1 is detected the vertical synchronizing signal which appears after read-out of field 2 will cause the track jump of the scanning spot, which means that the fields 1 2 are reproduced as Plink 87l7 14~6.77 a still picture.
If switching to the still-picture mode is effected one picture later, which will ye explaiIled subsequently, the scanning spot keeps following the inforlrlation track until the next indication signal (field 3) is detected, after which the second Verdi.-eel synchronizing signal which is detected after this again intuits the track jump, so that the fields 3 4 are then reproduced as a sti.l.l-pict~lre~ us is apparent from the table it is thus ensllred that the number of possibilities for reproduction in the still picture node is limited to combinations of fields which belong to the same set of fields.
Fix. 5 schematically Slows an e~arllple of the selection circuit which is based on prove-dune 1 in accordance with Fig. 4. The selection circuit comprises an input terminal 40 for the vertical synchronizing pulses F which are detected from the readout television signals by the detect ion 29 (Fig. 3). These vertical synchronizing put-sues F are applied to the clock input T of two JO-flip-flops 48 and 49. The J and the K inputs of the JO flip-flop 48 are respectively connected to the Q1 and Q1 outputs of a flip-flop 47, whilst the J and K inputs of the JO flip flop 49 are respectively connected to the Q2 and the Q2~
outputs of the JO flip-flop 48, Lowe flip-flop 47 I .6,77 has a set input S which is connected to a circuit 46 This circuit 46 receives the field pulses at its input from which it derives pulses L which viewed in time are situated between the field pulses and, as the case may be, an indication signal associated with a relevant field. For this it is thus assumed that the indication signal is situated some time after the vertical synchronizing signal. For this purpose the circuit 46 may for example consist of a monostablc multi vibrator which is triggered by the trailing edge of a field pulse. The selection circuit furthermore comprises two AND gates 50 and 51. The Negate 50 comprises three inputs which are rest pectively connected to the Q2 output of JO flip-flop 48, the Q3 output of JO flip-flop 49, and the 0lltpUt of circuit 46. The AND-gate 51 comprises three inputs which are respectively connected to the output of the circuit 46, the output Q3 of the JO flip-flop 49 and a control terminal 44. The out-puts X and Y of these two AND-gates 50 and 51 are connected to the inputs of an OR-gate 52, whose output Z is connected to an output terminal 45.
This Olltput terminal 45 constitutes the Oll-tpUt of the selection circuit and consequently corresponds to the output of` the circuit 31 in jig. 3.
The selection circuit of Fig. 5 further-more comprises an input terminal 41 to which the 7 1 if . 6 . 7 7 indication signals B detected by the detector 30 (Fugue) are applied. This indication signal B is --- applied via an inventor 53 to the clock input T of a JO flip-flop 54. The J-input of said JO flip-flop is connected to an input terminal ~12, which via an invert0r 55 is connected to the Input of JO flip-flop 54. The outputs Q4 and Q4 of JO flip-flop 54 are connected to the J and K input respect lively of a JO flip-flop 56, whose clock input T
also receives the inverted indication signals (pulses). The output Q5 of JO flip-flop 56 and the OUtpllt ELI Or the JO flip-flop 511 are collected to the illpU is o r an OR-gate 57 The circuit filially cor11pri.ses. antler AND-gate 58 with three illpUts which are respectively connected to an input ton-final ~13, the input terminal 41 and the output of the Ovate 58. The output W of this AND-gate is connected to -the reset inputs R of the flip-flops 47, 48 and 49.
The scanning mod of two read apparatus is determined by the logic levels of the control signals C, Dank A at the respective control ton-finals 43, 44 and 42. In the following table the combinations of logic levels of these control sign nets in -the corresponding scanning modes are in dilated.
PIN ~717 . 14.G.77 , , _ .
C D A Mode _ . .. _ . Jo 0 0 _ nornlal forward 0 1 _ backward 1 _ 0 still-picture 1 O 0 O one picture forward __ 1 O O one picture backward As long as the signal C is a logic 0 either normal scanning of -the recorded video signal is ox-trained (D - 0) or the recorded programmc is scanned backwards (D 1). Sign]. A is then irrelevant, If signal C is a logic 1 and signal A a logic 0 the still picture mode is switched on irrespectively of signal D. If the signal A is a logic 1 for a certain time, one picture is scanned in the forward direction (D = 0) or one picture is scanned in the backward direction (D - 1).
The operation of the selection circuit of Fig. 5 will now be described in more detail with reference to the timing diagrams in Figs. pa, 6b and 6c, which give the signals at the various points of the circuits in the various scanning modes.
Hcreillafter the signals at the various points Q1 through Q5, Lo I, Y, Z etc. will be de-1~.6.77 signaled by the same reference letters as the points themselves. The signal Q1 thus means the signal at the OUtpllt Al of the flip-flop 47 etc. Furthermore Fig, 7 schematically shows the corresponding scan-nine sequence of a number of consecutive pictures recorded on the record carrier. The vertically plotted units represent a sequence of fields no-corded on the disc, i.e. together a part of the spiral track. The first two yields fur example stem from a film frame n-3, the following three fields from a filrl1 frame n-2 etc. To each set of fields an India cation signal has been added to the first yield which is indicated ill the Figure by the number of the relevant Illume frame. The time axis has been plotted horizon-tally, so that the diagram shown gives the scanning sequence of the recorded fields.
It is assumed that the control signal C at the control terminal 43 is a logic "0". This means that the output signal W of the AND gate 58 is always "0", so that the lip flops 47, 48 and 49 receive no reset pulses. The first pulse L at the set input S of the flip-flop 47 will make the sign net Q1 "1", a sub 9 sequent field pulse F at the clock illpUt T of JO flip-flop 48 will make the signal Q2 "1", and the next field pulse F at the clock input T of the JO flip fop Is will mike the signal Q3 "1". This situation is continuous-1 7 PUN ~717 11~.6.77 lye maintained as long as the signal C at the control input 43 remains "0", i.e. as long as the flip-flops 47, 48 and lo receive no reset pulses, It is assumed that this situation exists at the instant to in the time diagram ox Fix. pa so that all outputs Q1' Q2 and Q3 supply a "1" signal. This means that the sign net X at the output of the AND-gate 50 is always "0", because the signal Quiz "0". The signal Y a-t the output of the AND-gate 51 depends on the control signal D at; the control terminal ll4. It is assumed that this control signal D is "0", so that Y is also "0". This also means that a signal Z at -the output of the Ovate 52 is always "0". Consequently, at the output terminal 1~5 Of said selection circuit no comlnand pulse appears which, via the switch 26 shown in lug. 3 and' signal source 32, can cause a track jump of the scannillg spot. this means -that the spiral track on the record carrier is scanned continuously, so that consecutively -the fields eon-responding to the film frames no and no are read.
At the instant to (Fig. aye the control signal C at the terminal Lo its switched to "1".
As it is assumed that the control signal A at the control terminal 42 is arrowhead 1'0-l at least from the instant to the signals Al and Q5 are both "O".
As the signal ill is consequently "1", the next in-1l~.6.77 dilation pulse B at the output W of the AND-gate 58 results in a pulse which resets the three flip-flops 48 and 49, so that the signals Q1' Q2 and Q3 become zero. The signal Al becomes "1" again owing to the next pulse of the signal L from the circuit 46. The signal Q2 becomes "1" owing to the -field pulse F
which then follows. The two signals Q1 and Q2 be-come "O" again owing to the next pulse W from the AND-gate 58 to appear. The signal Q3 remains always "O" under these conditions.
~ithiIl the time interval between the in-slant that the signal Q2 becomes I owing to the appearance of a field pulse F and the install that said signal becomes "O" again owing to the occur-fence of a reset pulse W for the flip-flops 1~7 through I a pulse L from the circuit lo appears.
This pulse is transferred via the AND gate because the two other inputs of this gate receive a "1"
signal, so that at the output X of this AND-gate and thus at the output Z of the OR-gate 52 a pulse appears. This pulse causes a track jump of the scanning spot, so that the same turn of the track, i e. the same two fields, are read again. This is repeated as long as the control signals C, D and A
retain the specified vales During this time the read apparatus consequently remains in the still-picture mode.
21~ -- , 7 I/~.6.77 At the instant to (Fig. pa and 6b respect lively) tile control signal A at the control term-net 42 becomes "1" for a certain tine (at least for three field periods At the trailing edge of the next indication pulse Pun the signal Q4 from flip-flop 54 becomes I This indication pulse on also results in a reset pulse (signal W from the AND-gate 58) for the flip-flops 47 through 49. The next indication pulse B , however does not have this effect,, because at the instant at which the text indication pulse B occurs, both the signal Q4 from tile flip-flop 54 and the signal Q5 from flip-flop 56 are "O", so that the output signal of the Ovate 57 is "O" and the AND-gate 58 is consequently closed. At the trailing edge of this indication pulse B Q5 becomes "1" again, so that after this instant the OR-gate 57 again supplies an "1" to the AND-gate 58.
, Owing to the absence of a reset pulse W
for the flip-flops 47 through 49 which coincides with the indication pulse B not only the signals Al Q2 from the flip-flops 47 and 48 respectively become "1", 'but also tile signal Q3 from the flip-flop 49. As long as this solely Q3 is "'I", i.e.
the signal Q3 its I the AND-gate 50 is closed.
As AND-gate 51 is also closed by the control signal D, output terminal 45 cannot supply a command pulse, I Z 84l7 PIN 8717 14.6.77 so that no tragic my is effected. Consequelltly the scamlin~ spot keeps following the spiral track us-ill the indication pulse Bn~l associated with the next film frame is detected. us at this instant Q5 S is still I this indication pulse Bn~1 via the AND-gate 58 provides a reset pulse W for the flip-flops 47 through 49, as a result of which in a six miter way as in the time interval t1-t2 the de sir-Ed command plilses (Z) are obtained with the air of the flip lops 47 thrill 49 and the gates 50 through 52, so that low the fields corre4pondiIlg to the film-frame no are reproduced in the still-picture mode.
For switch one placatory backwards the control signal A is switched to I for a certain time at the instant to, and simultaneously the con-trot signal D becomes "1", In a similar way as when wow taking one picture forwards one of the reset pulses (W) for the flip-flops thereof 49 is suppressed, so that after the signals Q1 and Q2 have become "1, thy signal Q3 also becomes "1".
Negate 50 is closed during the time that the sign at Q3 is "1", i.e. signal Quiz JO". The AND-gate Sly however is open during this time so that the signal Y consists of a pulse train corresponding to the signal L from the circuit 46, Via the OR-gate 52 this pulse train is transferred to the output ton-final 45, so that after each field period a track jump Of the skimming spot is initiated. This Coil lt7 Lyle tinges until another indication pulse By is detected.
This indication pulse belongs to the preceding film frame and results in a reset pulse W, so what the still-picture mode its restored completely.
If the recorded programmer is to be played back in a backward direction, the control signal C
should become "0" whilst the control signal D is I'm", as is indicated at the instant to. The signal W consequently remains "0", so that no reset pulses are applied to the flip-flops 47 through 49. After some field pulses F all signals Q1' Q2 and Q3 are consequently "1". This mean that the Negate 50 is closed. The AND-gate 51, however, completely transfers the pulse train L to the OlltpUt ton-final 45, so that after each field period a track jump is initiated.
A fast forward scal1ning mode can be achieved by just reversing the polarity of` the control signal for the drive means 27 (jig. 3), which sign net is supplied by the signal source 32 and which is destined for effecting the track jump, due to which, a forward track jump will be effected after read-out Or one field, i.e. two fields are skipped.
With the example ox the selection circuit shown in jig. 5 it is thus possible to switch on -the various scanning modes by the application of the various collateral signals, whilst ensuring that in 3 Lo .6.77 the sti]l-picture mode only the first two fields stemming from one film frame are reproduced. Ox-piously, many variants of this circuit are posy Sibley It is to be noted that the embodiment shown is based on the requirement that in addition to provisions for the still-picture mode the nieces-spry provisions are taken for the other scanning modes. If only a still-pieture move is required, the selection circuit may of course be consider-ably simpler.
Revertillg now to the table of lug. 4, the remaining possibilities ox adding the i~dica--lion signal to the televisioll signal and deriving a command signal therefrom for initiating the track jump will be discussed now. In -the case of` the posy sublet given in row 2 the indication signal, ill a similar way as under 1, is always added to tile first yield of a set The command signal for initiating the track jump, however, is now not derived from the rtical synchronizing signal but from the indication signal B itself'. Thus the track jump is effected immediately after detect lion of the indication signal.
In the case of possibility 3 the India cation signal is added to the second field of each set, whilst the commaIld-signal for initiating the track jump is derived from the next vertical synchronizing signal. Thus, always the first and second field of a set are reproduced in the still.-picture mode entirely in accordance with possibly-try 1.
In the case of possibilities 4 and 5 only the second and third field of a set consist-in of 3 fields are reproduced in the still picture mode, the.positi.olls of the indication signals B and the eomm~ d ~:igrlals Z being apparent from the -table.
Under G a special possibility its jovial, one incaution signal 'be:i.llg added to each eornbi-nation of two conseclltive sets namely to tile first field of second set. to in the sty picture mode the indication sigllal B is low used as a command solely Z for initiating the track jump two fields of the first set are reproduced. Lowry if the second vertical. synchronizing signal 1~`2 after de-section of the indication signal is employed as a eornmarld signal Z, two fields of the second set are reproduced. By switching between these -two methods of obtaining the command signal,eonseeu-live phylum frames are reproduced in the still-picture mode.
For illustration Fig. 8 shows an example of the selection erect required for this. The section which should supply the second vertical 7 Lyon 8717 11~.6.77 synchronizing signal after the detection of an India cation signal B as a command signal, may be sub Stan-tidally identical to the corresponding section of the circuit of Fig 5 and comprises the flip-flops 47 7 I and 49, the AND-gate 50 and a circuit 46. The output signal X of the AND-gate 50 is applied to an AND-gate 62. This AND-gate 62 furthermore receives a signal from a control terminal 65, which is "1" ion the still-picture mode and a signal from a control terminal 60. If this last mentioned signal is also "1" the signal X via the Negate 62 and the I
gate 61l thus functions as a command signal Z for initiating the track jump, it the second vertical synchronizing signal F2 after detection of an India cation signal I. }Louvre if the control signal at the control terminal .60 is "0", tile AND-gate 6Z is closed. The commend signal Z it then con-stitutcd by the indication signal B itself which is thin transferred via an AND-gate 63 which also receives the control signal from terminal 60 via an inventor 61 and the solely at the control ton-rninal 65, Depending on the control signal at the control terminal 60 either the scene correspond-in to the first set of fields or the second set of fields is reproduced.
In respect of the position of the India cation signal within a field period and the shape I 7 Plink 8717 11~.6.77 of this signal the following is to be noted, As previously stated this indication signal is always recorded durillg the vertical blanking period in or-don not to disturb the picture to be reproduced.
certain picture line after the vertical synchronize in signal may then be reserved for the indication signal. In order to rminirnize the risk of interior-once, steps can be talc en to ensure that the detect lion of an indication signal is possible only in the relevant portion of the field period, for Wesley purr pose a gate circuit can be included before the detect Thor.
For the addition of an address signal it is for example possible to use a buffs signal with the signal values corresponding to white and black of the television signal as logic levels. A
number of bits may then serve as indication sign net, whilst the remaining bits may represent the picture number.
Finally, it is to be noted that the in-mention is by no means limiter to the embodiments shown. both in respect of the scanning sequence at the transitions between the various scanr~ng modes of the read apparatus and in respect of the design of the selection circuit many variants are possible.
This is a divisional of Canadian patent application Serial No. 298,552 filed March 9, 1978.
The invention relates to system for playing back a programmer recorded on a disc-shaped record car-nor, which system comprises a read apparatus for scanning the record carrier, said record carrier being provided with a spiral information track in which the programmer is recorded as a television signal in a sequence of two fields per turn of the track, and con-secutive scenes of the programmer on the record car-nor being constituted by consecutive sets of fields, each set comprising either two or three fields, in accordance with a regularly repeated pattern of sets and the read apparatus being provided with control means for realizing a still-picture mode, in which mode the same two consecutive fields are repeatedly read by the repeated scanning of the same turn of the track.
Currently disc-shaped record carriers come mend much interest as a storage-medium for video in-formation. This applies in particular to disc-shaped record carriers on which this video information is recorded in optically coded form. For reading these record carriers a read apparatus is employed which uses an optical scanning system. With the aid of a PUN. 8717.
beam of radiation a scanning spot is projected onto the record carrier and information which is contained in this radiation beam after interaction with the record carrier is detected and converted into a tote-vision signal which is suitable for reproduction vice standard television receiver. Control systems, which may inter aria comprise deflection means inter-posed in the radiation beam, ensure that the scanning spot always coincides with the spiral information track on the record carrier. Such read apparatus, in particular the control system used therein, is inter aria described in US. Patent Specification No.
3,854,015 which issued to US. Phillips Corporation on December 10, 1974.
The major advantage of using an optical coding on the record carrier in conjunction with an optical scanning system is that scanning is entirely con tactless, so that the risk of damage to the record carrier is minimized irrespective of movements of the scanning spot over the record carrier. During read-out this inter alias provides the possibility of using a still-picture mode, which possibility is comprehensively described in the above Patent Specific cation. In this still-picture mode the scanning spot is moved back radially by one track pitch after every revolution of the record carrier with -the aid of the deflection means, so that continually the same turn of '7 PIN. 8717.
the spiral track is scanned. As exactly -two fields are recorded in one turn of the track, which fields together constitute the interlaced television image, one specific picture of the recorded television signal is reproduced continuously in the still-picture mode.
Said record carriers are primarily intend-Ed to be provided with a programmer by the factor and thus to be made available to the consumer as prerecorded record carriers. The most likely pro-Grimm material for this type of prerecorded record carriers is constituted by film material because -this is available in large slot and in a wide repertory.
If a film programmer is to be used for the manufacture of record carriers destined for the American market, a complication results from the difference between the standards for the reproduction of film images and those for the reproduction of television pie-lures.
The standard mainly used for film inter a_ implies that 24 film frames per second are no-corded and reproduced. In order to convert such a film into a video signal which is suitable for no-cording on said disc-shaped record carriers, each film frame is scanned in accordance with a pattern of interlaced fields. However, in accordance with the United States television standard, 30 pictures PUN. 8717.
per second must be reproduced, so that it is not posy sidle to transform one film frame into one television picture because then the playback speed of the record-Ed programmer would then not be correct. The necessary adaptation can be obtained in known manner by program-mint the film scanner so that consecutive film frames are alternately converted into a set of two fields and a set of three fields. This means that two film frames are converted into five fields or four film frames into 10 fields or 5 television pictures, which correspond to a 24/30 conversion from the film standard into the television standard. In order to obtain this transformation it is not necessary per so to convert consecutive film frames into alternate sets of two and three fields. It is also possible to use a different sequential pattern. For example as an alternative four consecutive film frames may be converted into consecutive sets of two, three, three and two fields.
Any pattern with a period which is so short as not to be observed by the human eye may in principle be used.
If a read apparatus for disc-shaped record carriers is operated in the still-picture mode it is found that the reproduction quality is not always satisfactory when record carriers are used on which a television programmer is recorded which is obtained in the manner described above. Often the television picture which is reproduced in the still-picture '7 PUN. 8717.
mode exhibits blurring and in the case of certain programmer it is even completely unacceptable.
It is an object of the invention to imp prove this situation and the invention is kirk-terraced in that to at least one of the fields which together constitute a pair of consecutive sets of television fields on the record carrier an indication signal is added and that the read Papa-fetus is provided with detection means for detect-in this indication signal and with selection means which are coupled to said detection means and which co-operate with the control means, which selection means as a function of the detected indication sign net in conjunction with the control means, it adapted to select the two fields to be reproduced in the still-picture mode in such a way that the two fields reproduced belong to the same set of fields.
The invention is based on the recognition that in the still-picture mode of the known read apparatus two interlaced fields may be reproduced which stem from two consecutive film frames. As the scenes recorded in two consecutive film frames generally differs slightly, in particular in the case of fast-moving scenes in the recorded pro-Grimm, the fields stemming from these individual film frames will also differ. If these fields are I Lo PUN. ~717.
are then combined into a television image by inter-lacing, a blurred picture results.
This is largely avoided by the steps in accordance with the invention in that first of all during the recording of the video signal on the no-cord carrier an indication signal is added to each pair of consecutive sets of fields. By providing the read apparatus with detection means for detect-in this indication signal it is achieved that lo information is available in respect of the field which is being read at that instant during the still-picture mode. This information can be employed for programming the control means via selection means controlled by this indication signal in such a way that, in this mode, the two fields reproduced always stem from the same film frame.
Preferably an indication signal is added to each set of fields on the record carrier, be-cause in that case the selection means can be very simple.
The added indication signal may also serve as an address signal, ye. it may contain such a code that the indication signal after detection not only has the above mentioned function in the still-picture mode, but that after decoding of the code which is contained in each individual indication signal, it also provides a frame number associated with I I
PUN. 8717.
each film frame which may, for example, be displayed on the television screen simultaneously with the reproduced television picture or via a separate disk play.
Embodiments of -the invention will now be described, by way of example, with reference to the accompanying drawings, in which Figs. 1 and 2 schematically represent the manner in which a film programmer is recorded on a disc-shaped record carrier, Fig. 3 schematically shows the read appear-tusk for such a disc-shaped record carrier.
Fig. 4 in tabulated form shows the possible locations for the indication signal in consecutive sets of fields.
Fig. 5 shows a form of the selection means which may be used in the read apparatus of Fig. 3, Fig. 6 shows the signals appearing there-in in the various scanning modes, and Fig. 7 schematically represents the scan-nine sequence of the sets of fields thus obtained.
Fig. 8, which is on the same sheet as Fig. 5, finally shows an alternative form of the selection means.
Fig. lo schematically shows how a programmer recorded on film is reproduced. Each of the film frames I through IV is consecutively reproduced for PUN. ~717~
1/24 of a second. If such a film programmer is to be converted into a television signal, it is necessary to ensure that, per second, this television signal sequentially represents the information content of 24 consecutive film frames, preferably in an as regular as possible manner. To obtain a television signal in accordance with United States standards, which signal contains 60 fields per second, a con-version is necessary of which a possibility is repro-sensed in Fig. lb.
Fig. lb schematically represents the repro-diction of a television signal which consists of 30 television pictures per second. Each television, as is known, consists of two interlaced fields. Within a time interval of 1/6 of a second in which 4 film frames (I through IV) are reproduced it is therefore necessary to reproduce 5 television pictures of 10 fields (1 through 10). In order -to achieve this the film frames are converted in known manner into a television signal, which changes from film frame to film frame, with aid of film scanning equipment.
The first film frame I is scanned in accordance wit two fields 1 + 2 resulting in a television picture So (Fig. to) consisting of these two interlaced fields 1 + 20 The second film frame II is first of all scanned in accordance with two fields 3 + 4, resulting in a television picture So consisting of PUN. 8717.
these two interlaced fields 3 + 4, but subsequently this film frame II is again scanned in accordance with a field 5. Thus, in the television signal this film frame II is ultimately represented by three fields 3, 4 and 5. The next film frame III again yields two fields 6 + 7, film frame IV three fields 8, 9 and 10, etc.
The Figure readily shows that in the time interval (1/6 of a second) which is necessary for reproducing 4 film frames exactly 10 fields are no-produced, or 5 television pictures. Owing to the alternate sets of two and three fields per film frame the sequence of the original scenes recorded on the film will be slightly disturbed during nor-met reproduction, but because it is disturbed with frequency of 12 Ho this is hardly perceptible to the human eye.
Instead of the conversion illustrated in Fig. 1 i-t is readily possible to select a conversion in accordance with the film frames I and IV each no-suit into two fields and the film frames II and III
each in three fields. Moreover, a pattern of sets may be chosen which is divided among more than four film frames, each pat-tern comprising an equal numb bier of sets of two and of three fields.
If during read out of a disc-shaped record carrier the still-picture mode is selected it is PUN. 8717.
found that in certain cases an unacceptable picture, in particular a slurred picture is produced. It is found that such a blurred picture in -the still-picture mode may be attributed to the selected con-version of film frames into television signals This is illustrated by means of Fig. 2 in combination with Fig. 1.
As previously stated, the video signal is recorded in a spiral track on the disc-shaped record carrier, each turn of the track comprising two fields. Fig. 2 shows such a spiral track T. This track is scanned by a rotation of the record carrier in the direction P, namely from the inside towards the outside in the example shown. Assuming that recording of field 1 begins on the radius R, the fields 1 through 10 will occupy the indicated track portions, i.e. the odd yields the track portions to the right of the radius R and -the even fields the track portions to the left of the opposite radius to R. A sequence of odd and an even field always con-statutes one track circumference, corresponding to one television picture Sly S2,...S5.
In the still-picture mode of the playback apparatus one turn of the track is scanned contain-usual in that the scanning spot is moved backwardly over a distance equal to the track pitch I 7 1 I . 6 . 77 of the spiral track upon each revolution of the no-cord carrier, said movement being referred to here-inciter as track jump. Obviously, such a track jump is noteffeeted at an arbitrary instant, but always during the vertical fly back of the reproduced lo-Louisiana signal, in order not to disturb the disk played picture. furthermore it its common practice for the track jump to coincide with the beginning of the odd fields by detection of the ~ertieal synchronizing signal, so that in the still-pieture mode pictures are repoured which always consist of an odd followed by an even field, i.e. eons-eutive pictures So, So, So eye. In the present example the track jump is therefore always effected at the location of the uninterrupted part of the diameter along R.
In the still picture mode the scanning spot for example follows the path indicated by the dashed line, so that the picture So consisting of the fields 1 and 2 is reproduced. This is found to be, an entirely correct picture. If in the still-picture mode the scanning spot follows the path in-dilated by the dashed-dot line, the picture So con-sitting of the fields 5 6 is reproduced. In Fig.
1 it can be seen that the two fields 5 and 6, which in interfaced form constitute said picture So, stem from two different film frames, namely the frames . - 12 I
14.6.77 ;
- II and III respectively. These two fields will cons-quaintly represent different scenes which in the still-picture mode are then alternately reproduced for 1/60 sea, resulting in an unacceptable picture.
The picture So, consisting of the fields 5 + 6 it therefore not suitable for reproduction in the still-picture mode. The same applies to the picture So, consisting of the fields 7 8, as can readily be seen in Fig. 1.
' In accordance with the invention indication signals are added to the recorded video signal in or-dyer to prevent these problems in the still-picture mode of the read apparatus. These indication signals are detected during read-out and together with the selection means, which are responsive to these in dilation signals, they ensure that in the still-picture mode only combinations of two fields which stem from the same film frame are reproduced.
To explain the operation of the system in accordance with the invention Fig. 3 schematically shows an embodiment of an optical read apparatus.
This read apparatus largely corresponds to that shown and comprehensively described in the said Patent Specification No. 1,429,882.
The disc-shaped record carrier 11 is driven in a rotary sense 13 about its center 12 and comprises a spiral information track T. The . 7 PIN 8717 . 7 7 optical scanning system comprises a radiation source 14 which produces a radiation beam 15. This radiation beam is focused to a scanning spot I via the semi-transparent mirror 16, the mirror 17 and the tense 18. After reflection the radiation beam is again incident on the mirror 17 and the semi-transparent mirror 16 by which it is partly reflected to a de-Hector Z0. This detector first of all serves to de-toot the video information contained in the radiation bean and make Kit available at a terminal 21.
Moreover it is assumed that the radian lion beam which is incident on the detector 20 contains information relating to the radial post-lion of the scanning spot 19 relative to the inform motion tract, which results in a control signal at the terminal 22. Systems for obtaining this inform motion relating to the radial position of the scan-nine spot are known in a multitude of variants. As it is irrelevant for the present invention which system is used for this purpose, reference is mere-my made, by way of example, to the possibilities described in the said Patent Specification. The control signal which is available at the terminal 22 is applied to a drive means 27 via a control amplifier 25 and the switch 26~ which drive means can rotate the rotatable journal led (point 28) mirror 17 in the direction 33. Thus a closed con-7 14.6.77 trot system is obtained for controlling the radial position of the scanning spot 19, so that it is ensured that the scanning spot lo always coincides with the information track T.
in the still-picture mode of the read apt pyrites the scarLning spot lo should radially be move Ed back by one tragic pitch of the spiral track at every revolution of the record carrier 11. on or-don to achieve this the control loop of the radial tracking system is briefly rendered inoperative once per revolution of the record carrier, in that for example this loop is interrupted by the change-over of the switch 26. During this short time a signal source 32 then supplies a suitable control signal (jump signal) to the drive means 27 via the switch 26, so that the mirror 17 is rotated in such a way that the scanning spot 19 is rapidly moved by one track pitch in the radial direction.
Subsequently, the control loop is again closed by means of the switch 26, so that during the rest of the revolution of the record carrier the in-formation track is normally followed.
The control signal for the switch 26 and the signal source 32 is supplied by a selection Z5 circuit 31, which has two inputs which are connect-Ed to two separate detection circuits I and 30.
Both detection circuits receive *he television signal 14.6.77 weakly is taken from the terminal 21 of the detector 20 and which is decoded with the aid of a decoding device 23, from which signal they extract the Yen-tidal synchronizing signals (detector 29) and the indication signals B (detector 30~. The detection of the two signals jointly defines the instant in the stil].-picture mode at which the control loop of the radial tracking system is interrupted and the jump signal is applied to the dry means 27 of the mirror 177 in other words the instant at weakly -the track jump of the scanning spot is per-formed.
By a suitable choice of the position of the indication signal. within a set of fields on the record carrier in conjunction with a suitable design of the selection circuit, it is then posy sidle to ensure that in the still-picture mode always two fields are reproduced which stem from one end the same film frame. In respect of the pox session of the indication signal within the sets of fields on the disc in conjunction with the design of the selection circuit there are a number of posy sibilities. The most significant possibilities are schematically shown in Fig. 4 in the form of a table.
In Fig. 4 in the upper part of the table fields are indicated along a time axis t, showing ~;~2~17 PUN 871 7 11~.6.77 that the fields 1 and 2 stem from film frame I, fields 3, 4 and 5 from fill frame III, and fields 6 and 7 from fillrl frame III. In the rows 1 through 6 so-venal possibilities for the location of the indict-lion signal are given, which location is further specified in Callahan B. Column Z indicates at which instant the track jump occurs.
or the sake of clarity possibility 1 is considered first. As is indicated in the table by crosses an indication signal is added to the first field (r1) of each set (I, II, etc.) of fields, i.e. to the fields 1, 3, 6, etc. It is evident that tilts indication signal is included in the non-visible part of the television signal, i.e. in tile vertical planking period, nclmely after the vertical synchronizing signal. The selection circuit in the playbacli apparatus ma-y now be designed so that the control signal which causes the track jump in the still-picture mode is produced by the second Yen-tidal synchronizing signal (represented by I in calmly Z) after detection of the indication signal.
If the still-picture mode is switched on and sub-sequently the indication signal associated with field 1 is detected the vertical synchronizing signal which appears after read-out of field 2 will cause the track jump of the scanning spot, which means that the fields 1 2 are reproduced as Plink 87l7 14~6.77 a still picture.
If switching to the still-picture mode is effected one picture later, which will ye explaiIled subsequently, the scanning spot keeps following the inforlrlation track until the next indication signal (field 3) is detected, after which the second Verdi.-eel synchronizing signal which is detected after this again intuits the track jump, so that the fields 3 4 are then reproduced as a sti.l.l-pict~lre~ us is apparent from the table it is thus ensllred that the number of possibilities for reproduction in the still picture node is limited to combinations of fields which belong to the same set of fields.
Fix. 5 schematically Slows an e~arllple of the selection circuit which is based on prove-dune 1 in accordance with Fig. 4. The selection circuit comprises an input terminal 40 for the vertical synchronizing pulses F which are detected from the readout television signals by the detect ion 29 (Fig. 3). These vertical synchronizing put-sues F are applied to the clock input T of two JO-flip-flops 48 and 49. The J and the K inputs of the JO flip-flop 48 are respectively connected to the Q1 and Q1 outputs of a flip-flop 47, whilst the J and K inputs of the JO flip flop 49 are respectively connected to the Q2 and the Q2~
outputs of the JO flip-flop 48, Lowe flip-flop 47 I .6,77 has a set input S which is connected to a circuit 46 This circuit 46 receives the field pulses at its input from which it derives pulses L which viewed in time are situated between the field pulses and, as the case may be, an indication signal associated with a relevant field. For this it is thus assumed that the indication signal is situated some time after the vertical synchronizing signal. For this purpose the circuit 46 may for example consist of a monostablc multi vibrator which is triggered by the trailing edge of a field pulse. The selection circuit furthermore comprises two AND gates 50 and 51. The Negate 50 comprises three inputs which are rest pectively connected to the Q2 output of JO flip-flop 48, the Q3 output of JO flip-flop 49, and the 0lltpUt of circuit 46. The AND-gate 51 comprises three inputs which are respectively connected to the output of the circuit 46, the output Q3 of the JO flip-flop 49 and a control terminal 44. The out-puts X and Y of these two AND-gates 50 and 51 are connected to the inputs of an OR-gate 52, whose output Z is connected to an output terminal 45.
This Olltput terminal 45 constitutes the Oll-tpUt of the selection circuit and consequently corresponds to the output of` the circuit 31 in jig. 3.
The selection circuit of Fig. 5 further-more comprises an input terminal 41 to which the 7 1 if . 6 . 7 7 indication signals B detected by the detector 30 (Fugue) are applied. This indication signal B is --- applied via an inventor 53 to the clock input T of a JO flip-flop 54. The J-input of said JO flip-flop is connected to an input terminal ~12, which via an invert0r 55 is connected to the Input of JO flip-flop 54. The outputs Q4 and Q4 of JO flip-flop 54 are connected to the J and K input respect lively of a JO flip-flop 56, whose clock input T
also receives the inverted indication signals (pulses). The output Q5 of JO flip-flop 56 and the OUtpllt ELI Or the JO flip-flop 511 are collected to the illpU is o r an OR-gate 57 The circuit filially cor11pri.ses. antler AND-gate 58 with three illpUts which are respectively connected to an input ton-final ~13, the input terminal 41 and the output of the Ovate 58. The output W of this AND-gate is connected to -the reset inputs R of the flip-flops 47, 48 and 49.
The scanning mod of two read apparatus is determined by the logic levels of the control signals C, Dank A at the respective control ton-finals 43, 44 and 42. In the following table the combinations of logic levels of these control sign nets in -the corresponding scanning modes are in dilated.
PIN ~717 . 14.G.77 , , _ .
C D A Mode _ . .. _ . Jo 0 0 _ nornlal forward 0 1 _ backward 1 _ 0 still-picture 1 O 0 O one picture forward __ 1 O O one picture backward As long as the signal C is a logic 0 either normal scanning of -the recorded video signal is ox-trained (D - 0) or the recorded programmc is scanned backwards (D 1). Sign]. A is then irrelevant, If signal C is a logic 1 and signal A a logic 0 the still picture mode is switched on irrespectively of signal D. If the signal A is a logic 1 for a certain time, one picture is scanned in the forward direction (D = 0) or one picture is scanned in the backward direction (D - 1).
The operation of the selection circuit of Fig. 5 will now be described in more detail with reference to the timing diagrams in Figs. pa, 6b and 6c, which give the signals at the various points of the circuits in the various scanning modes.
Hcreillafter the signals at the various points Q1 through Q5, Lo I, Y, Z etc. will be de-1~.6.77 signaled by the same reference letters as the points themselves. The signal Q1 thus means the signal at the OUtpllt Al of the flip-flop 47 etc. Furthermore Fig, 7 schematically shows the corresponding scan-nine sequence of a number of consecutive pictures recorded on the record carrier. The vertically plotted units represent a sequence of fields no-corded on the disc, i.e. together a part of the spiral track. The first two yields fur example stem from a film frame n-3, the following three fields from a filrl1 frame n-2 etc. To each set of fields an India cation signal has been added to the first yield which is indicated ill the Figure by the number of the relevant Illume frame. The time axis has been plotted horizon-tally, so that the diagram shown gives the scanning sequence of the recorded fields.
It is assumed that the control signal C at the control terminal 43 is a logic "0". This means that the output signal W of the AND gate 58 is always "0", so that the lip flops 47, 48 and 49 receive no reset pulses. The first pulse L at the set input S of the flip-flop 47 will make the sign net Q1 "1", a sub 9 sequent field pulse F at the clock illpUt T of JO flip-flop 48 will make the signal Q2 "1", and the next field pulse F at the clock input T of the JO flip fop Is will mike the signal Q3 "1". This situation is continuous-1 7 PUN ~717 11~.6.77 lye maintained as long as the signal C at the control input 43 remains "0", i.e. as long as the flip-flops 47, 48 and lo receive no reset pulses, It is assumed that this situation exists at the instant to in the time diagram ox Fix. pa so that all outputs Q1' Q2 and Q3 supply a "1" signal. This means that the sign net X at the output of the AND-gate 50 is always "0", because the signal Quiz "0". The signal Y a-t the output of the AND-gate 51 depends on the control signal D at; the control terminal ll4. It is assumed that this control signal D is "0", so that Y is also "0". This also means that a signal Z at -the output of the Ovate 52 is always "0". Consequently, at the output terminal 1~5 Of said selection circuit no comlnand pulse appears which, via the switch 26 shown in lug. 3 and' signal source 32, can cause a track jump of the scannillg spot. this means -that the spiral track on the record carrier is scanned continuously, so that consecutively -the fields eon-responding to the film frames no and no are read.
At the instant to (Fig. aye the control signal C at the terminal Lo its switched to "1".
As it is assumed that the control signal A at the control terminal 42 is arrowhead 1'0-l at least from the instant to the signals Al and Q5 are both "O".
As the signal ill is consequently "1", the next in-1l~.6.77 dilation pulse B at the output W of the AND-gate 58 results in a pulse which resets the three flip-flops 48 and 49, so that the signals Q1' Q2 and Q3 become zero. The signal Al becomes "1" again owing to the next pulse of the signal L from the circuit 46. The signal Q2 becomes "1" owing to the -field pulse F
which then follows. The two signals Q1 and Q2 be-come "O" again owing to the next pulse W from the AND-gate 58 to appear. The signal Q3 remains always "O" under these conditions.
~ithiIl the time interval between the in-slant that the signal Q2 becomes I owing to the appearance of a field pulse F and the install that said signal becomes "O" again owing to the occur-fence of a reset pulse W for the flip-flops 1~7 through I a pulse L from the circuit lo appears.
This pulse is transferred via the AND gate because the two other inputs of this gate receive a "1"
signal, so that at the output X of this AND-gate and thus at the output Z of the OR-gate 52 a pulse appears. This pulse causes a track jump of the scanning spot, so that the same turn of the track, i e. the same two fields, are read again. This is repeated as long as the control signals C, D and A
retain the specified vales During this time the read apparatus consequently remains in the still-picture mode.
21~ -- , 7 I/~.6.77 At the instant to (Fig. pa and 6b respect lively) tile control signal A at the control term-net 42 becomes "1" for a certain tine (at least for three field periods At the trailing edge of the next indication pulse Pun the signal Q4 from flip-flop 54 becomes I This indication pulse on also results in a reset pulse (signal W from the AND-gate 58) for the flip-flops 47 through 49. The next indication pulse B , however does not have this effect,, because at the instant at which the text indication pulse B occurs, both the signal Q4 from tile flip-flop 54 and the signal Q5 from flip-flop 56 are "O", so that the output signal of the Ovate 57 is "O" and the AND-gate 58 is consequently closed. At the trailing edge of this indication pulse B Q5 becomes "1" again, so that after this instant the OR-gate 57 again supplies an "1" to the AND-gate 58.
, Owing to the absence of a reset pulse W
for the flip-flops 47 through 49 which coincides with the indication pulse B not only the signals Al Q2 from the flip-flops 47 and 48 respectively become "1", 'but also tile signal Q3 from the flip-flop 49. As long as this solely Q3 is "'I", i.e.
the signal Q3 its I the AND-gate 50 is closed.
As AND-gate 51 is also closed by the control signal D, output terminal 45 cannot supply a command pulse, I Z 84l7 PIN 8717 14.6.77 so that no tragic my is effected. Consequelltly the scamlin~ spot keeps following the spiral track us-ill the indication pulse Bn~l associated with the next film frame is detected. us at this instant Q5 S is still I this indication pulse Bn~1 via the AND-gate 58 provides a reset pulse W for the flip-flops 47 through 49, as a result of which in a six miter way as in the time interval t1-t2 the de sir-Ed command plilses (Z) are obtained with the air of the flip lops 47 thrill 49 and the gates 50 through 52, so that low the fields corre4pondiIlg to the film-frame no are reproduced in the still-picture mode.
For switch one placatory backwards the control signal A is switched to I for a certain time at the instant to, and simultaneously the con-trot signal D becomes "1", In a similar way as when wow taking one picture forwards one of the reset pulses (W) for the flip-flops thereof 49 is suppressed, so that after the signals Q1 and Q2 have become "1, thy signal Q3 also becomes "1".
Negate 50 is closed during the time that the sign at Q3 is "1", i.e. signal Quiz JO". The AND-gate Sly however is open during this time so that the signal Y consists of a pulse train corresponding to the signal L from the circuit 46, Via the OR-gate 52 this pulse train is transferred to the output ton-final 45, so that after each field period a track jump Of the skimming spot is initiated. This Coil lt7 Lyle tinges until another indication pulse By is detected.
This indication pulse belongs to the preceding film frame and results in a reset pulse W, so what the still-picture mode its restored completely.
If the recorded programmer is to be played back in a backward direction, the control signal C
should become "0" whilst the control signal D is I'm", as is indicated at the instant to. The signal W consequently remains "0", so that no reset pulses are applied to the flip-flops 47 through 49. After some field pulses F all signals Q1' Q2 and Q3 are consequently "1". This mean that the Negate 50 is closed. The AND-gate 51, however, completely transfers the pulse train L to the OlltpUt ton-final 45, so that after each field period a track jump is initiated.
A fast forward scal1ning mode can be achieved by just reversing the polarity of` the control signal for the drive means 27 (jig. 3), which sign net is supplied by the signal source 32 and which is destined for effecting the track jump, due to which, a forward track jump will be effected after read-out Or one field, i.e. two fields are skipped.
With the example ox the selection circuit shown in jig. 5 it is thus possible to switch on -the various scanning modes by the application of the various collateral signals, whilst ensuring that in 3 Lo .6.77 the sti]l-picture mode only the first two fields stemming from one film frame are reproduced. Ox-piously, many variants of this circuit are posy Sibley It is to be noted that the embodiment shown is based on the requirement that in addition to provisions for the still-picture mode the nieces-spry provisions are taken for the other scanning modes. If only a still-pieture move is required, the selection circuit may of course be consider-ably simpler.
Revertillg now to the table of lug. 4, the remaining possibilities ox adding the i~dica--lion signal to the televisioll signal and deriving a command signal therefrom for initiating the track jump will be discussed now. In -the case of` the posy sublet given in row 2 the indication signal, ill a similar way as under 1, is always added to tile first yield of a set The command signal for initiating the track jump, however, is now not derived from the rtical synchronizing signal but from the indication signal B itself'. Thus the track jump is effected immediately after detect lion of the indication signal.
In the case of possibility 3 the India cation signal is added to the second field of each set, whilst the commaIld-signal for initiating the track jump is derived from the next vertical synchronizing signal. Thus, always the first and second field of a set are reproduced in the still.-picture mode entirely in accordance with possibly-try 1.
In the case of possibilities 4 and 5 only the second and third field of a set consist-in of 3 fields are reproduced in the still picture mode, the.positi.olls of the indication signals B and the eomm~ d ~:igrlals Z being apparent from the -table.
Under G a special possibility its jovial, one incaution signal 'be:i.llg added to each eornbi-nation of two conseclltive sets namely to tile first field of second set. to in the sty picture mode the indication sigllal B is low used as a command solely Z for initiating the track jump two fields of the first set are reproduced. Lowry if the second vertical. synchronizing signal 1~`2 after de-section of the indication signal is employed as a eornmarld signal Z, two fields of the second set are reproduced. By switching between these -two methods of obtaining the command signal,eonseeu-live phylum frames are reproduced in the still-picture mode.
For illustration Fig. 8 shows an example of the selection erect required for this. The section which should supply the second vertical 7 Lyon 8717 11~.6.77 synchronizing signal after the detection of an India cation signal B as a command signal, may be sub Stan-tidally identical to the corresponding section of the circuit of Fig 5 and comprises the flip-flops 47 7 I and 49, the AND-gate 50 and a circuit 46. The output signal X of the AND-gate 50 is applied to an AND-gate 62. This AND-gate 62 furthermore receives a signal from a control terminal 65, which is "1" ion the still-picture mode and a signal from a control terminal 60. If this last mentioned signal is also "1" the signal X via the Negate 62 and the I
gate 61l thus functions as a command signal Z for initiating the track jump, it the second vertical synchronizing signal F2 after detection of an India cation signal I. }Louvre if the control signal at the control terminal .60 is "0", tile AND-gate 6Z is closed. The commend signal Z it then con-stitutcd by the indication signal B itself which is thin transferred via an AND-gate 63 which also receives the control signal from terminal 60 via an inventor 61 and the solely at the control ton-rninal 65, Depending on the control signal at the control terminal 60 either the scene correspond-in to the first set of fields or the second set of fields is reproduced.
In respect of the position of the India cation signal within a field period and the shape I 7 Plink 8717 11~.6.77 of this signal the following is to be noted, As previously stated this indication signal is always recorded durillg the vertical blanking period in or-don not to disturb the picture to be reproduced.
certain picture line after the vertical synchronize in signal may then be reserved for the indication signal. In order to rminirnize the risk of interior-once, steps can be talc en to ensure that the detect lion of an indication signal is possible only in the relevant portion of the field period, for Wesley purr pose a gate circuit can be included before the detect Thor.
For the addition of an address signal it is for example possible to use a buffs signal with the signal values corresponding to white and black of the television signal as logic levels. A
number of bits may then serve as indication sign net, whilst the remaining bits may represent the picture number.
Finally, it is to be noted that the in-mention is by no means limiter to the embodiments shown. both in respect of the scanning sequence at the transitions between the various scanr~ng modes of the read apparatus and in respect of the design of the selection circuit many variants are possible.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Disc-shaped record carrier, on which a televi-sion signal is recorded as a sequence of sets of fields, two fields per track circumference, consecutive scenes of the recorded programme corresponding to consecutive sets of two and three fields in accordance with a speci-fic pattern characterized in that the record carrier further comprises detectable indicating signals, which indicate sets of two consecutive fields which correspond to a single scene of the recorded programme.
2. Disc-shaped record carrier as claimed in Claim 1, characterized in that the indication signals are inserted in vertical synchronizing signal periods of the television signal.
3. Disc-shaped record carrier as claimed in Claim 2, characterized in that the indication signals moreover serve as address signals for the associated set of fields.
4. Disc-shaped record carrier as claimed in any of Claims 1, 2 or 3, characterized in that the consecutive sets of fields comprise alternately two and three fields, and that indication signals are recorded in the record carrier such that the distance between succeeding indica-tion signals is alternately two and three fields.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000375053A CA1228417A (en) | 1977-03-17 | 1981-04-09 | System for playing back a programme recorded on a disc-shaped record carrier |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7702874 | 1977-03-17 | ||
| NLAANVRAGE7702874,A NL182687C (en) | 1977-03-17 | 1977-03-17 | SYSTEM FOR DISPLAYING A PROGRAM RECORDED ON A DISC REGISTRATION CARRIER, AND A READING DEVICE AND RECORD CARRIER FOR USE IN SUCH A SYSTEM. |
| CA000298552A CA1228416A (en) | 1977-03-17 | 1978-03-09 | System for playing back a programme recorded on a disc-shaped record carrier |
| CA000375053A CA1228417A (en) | 1977-03-17 | 1981-04-09 | System for playing back a programme recorded on a disc-shaped record carrier |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1228417A true CA1228417A (en) | 1987-10-20 |
Family
ID=25668663
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000375053A Expired CA1228417A (en) | 1977-03-17 | 1981-04-09 | System for playing back a programme recorded on a disc-shaped record carrier |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1228417A (en) |
-
1981
- 1981-04-09 CA CA000375053A patent/CA1228417A/en not_active Expired
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| Date | Code | Title | Description |
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| MKEX | Expiry |