Abstract:
An apparatus and method for recording both a television picture signal and a digital data signal onto one track of a video disk. The digital data is divided into fixed length blocks. The video synchronization pulse is detached from a previous field and the digital data is positioned to have a trailing end at the following video synchronization pulse. Therefore, after a predetermined delay, the modulated digital data and modulated television picture signals are added and recorded on the video disk.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates both to a video disk on which television picture signals are recorded, and to a recording and reproducing apparatus therefor. 
     2. Background of the Invention 
     Recently disks for recording information thereon with high density have been developed and have been commercialized. Typical examples thereof are video disks and digital audio disks. The disks are classified into several types. Of those, an optical type of video disk has a spectral distribution such as shown in FIG. 6. Specifically, a television picture signal is recorded by frequency modulation of a carrier wave of 8.1 MHz to make the synchronization chip level 7.6 MHz and make the white level 9.3 MHz. An accompanying audio signal such as a stereo signal, a bilingual signal, or the like, is recorded by frequency modulation of carrier waves at 2.3 MHz and 2.3 MHz. On the other hand, an optical type of digital audio disk has a spectral distribution such as shown in FIG. 7, and an EFM signal of a pulse-code-modulated stereo signal is recorded within a band not higher than about 2 MHz. In the above-mentioned video disk, the band below 2 MHz is substantially empty, and such an EFM signal can be recorded on the video disk with frequency-division multiplexing. In this case, the disk has such spectral distribution as shown in FIG. 8, and it is understood that the respective signals are fully separable. 
     FIG. 9 is a block diagram of a recording apparatus for the video disk. In the drawing, a television picture signal is processed by a pre-emphasis circuit 1 for pre-emphasizing the high-band component, modulated by a frequency modulator 2, and fed to an adder 3. On the other hand, two-channel audio signals are pre-emphasized by pre-emphasis circuits 4 and 5, modulated by frequency modulators 6 and 7, and fed to the adder 3. Another set of two-channel audio signals are digitized or pulse-code modulated (PCM) by a PCM encoder 8, eight-to-fourteen modulated (EFM) by an EFM encoder 9, filtered by a low-pass filter 10 for removing the unnecessary high-band component, and fed to the adder 3 through a pre-emphasis circuit 11. Accordingly, the adder 3 receives an FM signal of the picture signal, two FM signals of the two-channel audio signals, and an EFM signal of the other two-channel audio signals. These signals are added to each other by the adder 3, passed through a limiter 12 for adjusting the level, and fed to a light modulator 13. As a result, a laser beam emitted from a laser light source 14 is modulated corresponding to the signals and radiated through an objective lens 16 onto an original recording board 17 rotated by a motor 16 so as to record the signals thereon. A technique for producing disks from such an original recording board 17 is commonly known, and detailed description thereof will be omitted. 
     FIG. 10 is a block diagram of an apparatus for reproducing audio and video signals from such a disk made by the procedure as described above. In the drawing, a laser beam generated from a pickup 23 is radiated through an objective lens 24 onto a disk 22 rotated by a motor 21. The reflected light from the disk 22 is received by the pickup 23 through the objective lens 24 to thereby generate a reproduction signal. The reproduction RF signal is amplified by an amplifier 25. Of the amplified signal, an FM carrier component passed through a band pass filter 26 is fed to a frequency demodulator 27, demodulated thereby, and produced as a picture signal from a de-emphasis circuit 28. FM carrier components passed through band pass filters 29 and 30 are fed to frequency demodulators 31 and 32, demodulated thereby, and produced as two-channel audio signals from de-emphasis circuits 33 and 34, respectively. An EFM signal component separated by a low-pass filter 35 is fed through a de-emphasis circuit 36 successively to an EFM decoder 37 and a PCM decoder 38 to be first EF-demodulated and PC-demodulated thereby, so as to produce two-channel analog audio signals. Accordingly, a TV audience can desirably choose suitable hi-fi audio signals in conjunction with a picture signal. 
     As the EFM signal, it may be considered to record a digital data signal in place of the audio signal. Unlike the audio signal, the digital data signal is not always continuous, and therefore it is considered advantageous to made the digital signal have a block structure. However, because the clock frequency of the EFM signal is about 44.1 kHz and the frequency of the vertical synchronizing signal is 29.97 Hz, there exists no simple multiply proportional relation between the two. Accordingly, it is difficult to select the position of each data block and the length thereof. 
     SUMMARY OF THE INVENTION. 
     It is therefore an object of the present invention to solve the problem in the prior art as described above. 
     According to the present invention, in a video disk in which a television picture signal and a digital data signal are recorded on one and the same track thereof through frequency-division multiplexing, the digital data signal is divided into blocks each composed of a fixed number of bits, and a terminal part of each of the blocks is recorded in the vicinity of a position corresponding to a vertical synchronizing pulse located at the rearmost of a corresponding frame or field of a television picture signal. As a result, the digital data can be reliably read even in the case where jumping-back is repeated in a still picture reproducing operation or the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a recording apparatus according to the present invention; 
     FIG. 2 is a block diagram of a reproducing apparatus according to the invention; 
     FIG. 3 is a detailed block diagram of a part of the reproducing apparatus; 
     FIGS. 4A-4J are timing charts of the recording and reproducing operations; 
     FIG. 5 is an enlarged view of a part of the timing chart of FIGS. 4A-4J; 
     FIG. 6 is a graph showing the spectral distribution of an optical video disk; 
     FIG. 7 is a graph showing the spectral distribution of an EFM signal; 
     FIG. 8 is a graph showing the spectral distribution of an optical video disk carrying which the EFM signal recorded thereon; 
     FIG. 9 is a block diagram of a recording apparatus for a conventional optical digital audio disk; and 
     FIG. 10 is a block diagram of a reproducing apparatus for the conventional optical digital audio disk. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     1. The Disk and Recording Apparatus 
     FIG. 1 is a block diagram of an embodiment of the recording apparatus according to the present invention. In FIG. 1, the corresponding parts to those in FIG. 9 are correspondingly reference, and detailed description thereabout is omitted here. Although FIG. 9 shows the case where two-channel audio signals are fed to an EFM encoder 9 through a PMC encoder 8, FIG. 1 shows the case where a digital data signal is fed to an EFM encoder 9 through a memory 41. Of course, a changeover switch or the like may be provided so as to input a selected one of an audio signal and a digital data signal. A position detecting means 42 detects a predetermined position of the video signal to control the memory 41. The construction of other parts is similar to the construction shown in FIG. 9. Namely, a pre-emphasis circuit 1, a frequency modulator 2 and an adder 3 are provided for the picture signal. Pre-emphasis circuits 4 and 5 and frequency modulators 6 and 7 are provided for the two-channel audio signal. A low-pass filter 10 and a pre-emphasis circuit 11 are disposed in the path of the signal from the EFM encoder 9. A limiter 12, a light modulator 13, a laser light source 14, an objective lens 15, a motor 16, and a recording medium 17 are disposed in the path of the signal from the adder 3. 
     2. Operations of the Disk and Recording Apparatus 
     The operation of the disk and the recording apparatus will be described hereunder. The video signal and the two-channel audio signal are respectively processed by the pre-emphasis circuits 1, 4 and 5 and the frequency modulator 2, 6 and 7, and are then added to each other by the adder 3 in the same manner as described above. According to the present invention, the position detecting means 42 detects a predetermined position s on the picture signal. The position s is in the vicinity of a vertical synchronizing pulse which is one field before the television picture signal frame which corresponds to the present digital data signal. 
     Upon detection of the predetermined position s, the position detecting means 42 starts a timer operation and generates a control signal when a predetermined time T 1  has elapsed from the start of the timer operation to cause the memory 41 to output the digital data signal so far stored in the memory 41. For example, let V represent the length of one field, as shown in FIG. 5. In the case where the digital data signal for two blocks is recorded as described later, the timer T 1  is calculated by subtracting the length (about 2.5V) of two blocks after interleaving and the idle time T 2  from the time (3V) of three fields. If the idle time T 2  is disregarded, the time T 1  is about 0.5V. The digital data signal released from the memory 41 is fed to the EFM encoder 9 so as to be interleaved or the like, and then fed to the adder 3 through the pre-emphasis circuit 11 so as to be added to the frequency-modulated picture and audio signals. Accordingly, the digital data signal is recorded with the result that the terminal part of the digital data signal is disposed in the vicinity of a position corresponding to the vertical synchronizing pulse at the rearmost of the corresponding frame. 
     The length of one block of the digital data signal can be determined arbitrarily to be 1 kbytes, 2 kbytes, or the like. For example, in the optical audio disk, one block of the audio signal before EF-modulation is made up of a digital data signal of 2.352 (=24×98) kbytes, that is, 18.816 kbits, corresponding to the block length of 98 frames, each frame being equivalent to 24  bytes. The length of one block of digital data signal before interleaving is about 13.3 ms but the length of one block after interleaving becomes about 28 ms. The difference arises because of the time overlapping on the optical digital audio disk owing to interleaving by the EFM encoder is about 14.7 ms. Because the pulse period of the vertical synchronizing signal (that is, the length of one field) is about 16.7 ms, the length of one block before interleaving is shorter than the pulse period of the vertical synchronizing signal (that is, the length of one field) but the length of the block after interleaving is longer than the length of one field and shorter than the length of one frame (FIG. 5). Accordingly, in the case, for example, as shown in FIG. 4C, a group of two blocks of the digital data signals Da 1  and Da 2 , another group of two blocks of the digital data signals Db 1  and Db 2  a, and so on, are separated from each other in respective frames. These pairs of blocks Da 1 , Da 2  and Db 1 , Db 2  are made to respectively correspond to the picture signal frames A and B. As shown in FIG. 4E, the terminal part in each of the last blocks D&#39;a 2 , D&#39;b 2 , and so one, in the respective frames A and B after interleaving is recorded in the vicinity of a position corresponding to the vertical synchronizing pulse of FIG. 4F disposed at the rearmost of the corresponding frame of FIG. 4E. Alternatively, in the case where all the blocks are separated from each other in every field, as shown in FIG. 4B, the terminal part in each of the blocks D&#39;a 1 , D&#39;a 2 , D&#39;b 1 , D&#39;b 2 , D&#39;c 1 , and so on, after interleaving, as shown in FIG. 4D, is recorded in the vicinity of a position corresponding to the vertical synchronizing pulse disposed at the rearmost of the corresponding field. Since jumping-back in reproduction should be made within a period of vertical retrace (about 0.07V), the recording apparatus is preferably designed so that the digital data signal is not recorded within a period of vertical retrace containing a vertical synchronizing pulse at the timing for jumping back. Thus, adjacent blocks are convoluted. At this time, the terminal part of the respective blocks D&#39;a 1 , D&#39;a 2 , D&#39;b 1 , D&#39;b 2 , and so on, after interleaving, as shown in both FIGS. 4D and 4E, are always at positions corresponding to the respective insides of the corresponding the fields A 1 , A 2 , B 1 , B 2 , and so on, because the terminal end of the last block is disposed in the vicinity of the vertical synchronizing pulse being at the rearmost of the corresponding frame or field. 
     3. The Reproducing Apparatus 
     FIG. 2 is a block diagram of a reproducing apparatus according to the present invention. In FIG. 2, the parts corresponding to those in FIG. 10 are corresponding referenced and their detailed description is omitted here. In the reproducing apparatus of the invention, the output of an EFM decoder 37 is fed selectively to a data decoder 52 or a PCM decoder 38 through a switch 51. The switch 51 is changed over in response to an instruction from a microcomputer not shown or the like such that the switch 51 turns to the side of a PCM decoder 38 when an audio signal is recorded as an EFM signal, while the switch turns to the side of a data decoder 52 when a digital data signal is recorded. In the case where the PCM decoder 38 can be used also for the digital data signal, it is matter of course that the data decoder 52 may be omitted and that the switch 51 may be provided at the output side of the PCM decoder 38. A switch 53 is used for squelching a picture signal derived from a de-emphasis circuit 28. A tracking control circuit 54 comprises an equalizer 55 for receiving a tracking error signal generated from an amplifier 25, a tracking servo loop switch 56, an adder 57, and a driving amplifier 58 for driving a tracking actuator not shown. 
     The picture signal from the de-emphasis circuit 28 is successively fed to a synchronizing separation circuit 59 and a vertical synchronizing separation circuit 60, so that a vertical synchronizing signal is separation-detected. The detection signal of the vertical synchronizing signal is fed to both a jump pulse generating circuit 61 and a squelch control circuit 62. A memory control circuit 63 controls a memory (RAM 75 in FIG. 3) of the data decoder 52. The jump pulse generating circuit 61, the squelch control circuit 62 and the memory control circuit 63 respectively receive a jumping instruction signal, a squelching instruction signal and a memory control signal which are generated from the microcomputer. 
     4. Operation of the Reproducing Apparatus 
     The operation of the reproducing apparatus, in the case where the EFM signal is not used as a digital data signal, is the same as described above, and the operation of the reproducing apparatus, in the case where in EFM signal is used as a digital data signal, will be described hereunder. For example, when an instruction to search a frame A or a digital data block D&#39;a 2  is issued from the microcomputer, the loop switch 56 is opened by the microcomputer to thereby start the operation of searching the frame A or the digital data block D&#39;a 2 . At the same time, the switch 53 is opened by the squelch-control circuit 62 to thereby squelch the picture signal. When the frame A or the block D&#39;a 2  is found, the loop switch 56 is closed to thereby operate the tracking control circuit. Thus, a normal reproducing operation starts from the head position of the frame A. 
     An EFM signal, in the reproduction signals from the amplifier 25, is fed through a low-pass filter 35 and a de-emphasis circuit 36 to the EFM decoder 37 so as to be EF-demodulated. The EF-demodulated signal is fed to the data decoder 52 through the switch 51, and stored in a predetermined address of the memory corresponding to the signal from the memory control circuit 63. When the storing operation for the digital data block D&#39;a 2  is terminated, as shown in FIGS. 4I or 4J, a jumping instruction is issued to the jump-pulse generating circuit 61. In response to this instruction, the jump-pulse generating circuit 61 generates a jump pulse to the adder 57 at the timing where a vertical synchronizing pulse can be detected from the vertical synchronizing separation circuit 60 after a lapse of the time T 2 . Accordingly, the tracking actuator is operated so that the pickup 23 jumps back by one track (one frame) from the vicinity of the vertical synchronizing pulse being at the rearmost of the frame A to the vicinity of the vertical synchronizing pulse being at the frontmost of the frame A. Thereafter, the operation of reproducing the frame A and the operation of jumping back by one track are alternately repeated to thereby perform stationary reproduction of the frame A, as shown in FIG. 4G. 
     On the other hand, when the position of the vicinity of the vertical synchronizing pulse being at the frontmost of the frame A is detected, the squelch-control circuit 62 closes the switch 53 to thereby terminate the squelching state. Accordingly, users can observe a still picture of the frame A, as shown in FIG. 4H. When processing of the digital data signal is terminated, the still picture reproducing operation is released and the operation shifts to the next one. 
     While the pickup 23 is jumping back, the first one D&#39;a 1  of the two blocks of data cannot be reproduced completely. To solve the problem, the two blocks of data may be made to have the same contents, so that in the normal reproducing operation, if one block drops out the other block is read. On the other hand, in the still picture reproducing operation, only the rear one of the two blocks is read with the front one disregarded. Of course, alternatively, the two blocks may be made to have different data contents, so that in the still picture reproducing operation, the front one of the two blocks is disregarded. Alternatively, the data processing may be designed to read the front block D&#39;a 1  after the reproduction from the vicinity of a vertical synchronizing pulse immediately before the front block Da 1  to the vicinity of another vertical synchronizing pulse immediately after the same front block D&#39;a 1 . Then, the operation is repeated of reproducing the still picture of the frame A till the completion of the reading process. Data processing is performed for the temporarily stored front block D&#39;a 1 , and data processing is performed for the next block D&#39;a 2 . In any case, the successively stored terminal part of each block is made to correspond to a vertical synchronizing pulse just before jumping, so that the data to be reproduced during a time where tracking is in an unstable state after jumping is the data of the front block which is to be disregarded and the rear block is reproduced when tracking is in a stable state. Accordingly, it is possible to prevent an error in reading of data caused by the jumping operation. 
     FIG. 3 is a block diagram showing the EFM decoder 37 and the data decoder 52 in more detail (in the drawing, the switch 51 between the two decoders is omitted). In the EFM decoder 37, the EFM signal fed thereto is shaped by a wave-shaping circuit 71, demodulated by an EFM demodulator 72, temporarily stored in a RAM 73 (for example, of 16 kbits), and corrected by an error detecting and correcting circuit 74 after processing such as de-interleaving or the like. On the other hand, in the data decoder 52, the digital data is temporarily stored in a RAM 75 and corrected by an error detecting and correcting circuit 76 after processing such as de-interleaving or the like by means of the control signal from the memory control circuit 63. If the RAM 75 is made to have a capacity corresponding to an amount of two blocks, that is, about 38 kbits, it is possible to store picture data for one screen at the same time. The capacity of the RAM 75 may be selected to be an amount of one block, that is, about 19 kbits. 
     As described above, the present invention can provide a video disk in which a television picture signal and a digital data signal are recorded on one track with frequency-division multiplexing. The digital data signal is divided into blocks each composed of a predetermined number of bits. A terminal part in each of the blocks is recorded in the vicinity of a position corresponding to a vertical synchronizing pulse disposed at the rearmost of a corresponding television picture signal frame or field. Accordingly, even if tracking is in an unstable state owing to a jumping-back operation effected in a still picture reproducing operation, or the like, digital data can be reliably read. Furthermore, each block of digital data can be made to correspond to a frame or a field to thereby simplify searching and reproducing of a predetermined picture scene or digital data. In addition, the time required for squelching the picture signal can be shortened.