JP3336766B2 - Tracking control device and magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumer digital VT
Tracking control device and a child in a variable speed reproduction of R
The present invention relates to a magnetic recording / reproducing apparatus using the same .

[0002]

2. Description of the Related Art In a consumer digital VTR, an image compression technique such as the MPEG system is used to reduce the amount of data recorded on a magnetic tape. In the MPEG system,
Since the video is constructed using the difference between the frames,
When performing variable-speed playback or the like, the continuity of the data of the preceding and following frames is lost, so that it is not possible to restore the video from the played back data. For this reason, as a variable speed reproduction method of a digital VTR using the MPEG system for image compression,
For example, "FIRST SCAN TECHNOLOGY FOR DIGITALVIDEO T
APE RECORDERS (IEE Transactions on Consumer Elect
ronics Vol.39, No.3, AUGUST 1993)). As shown in FIG. 10, this method uses a reproducing head so that an image can be decoded even during variable speed reproduction. The variable speed playback video data 72 is recorded separately from the normal playback video data 24 at a specific position on the magnetic tape 21 corresponding to the scanning locus 71 of the 22 to form a track 73 for variable speed playback. Each track is composed of a plurality of data blocks of about several hundred bytes, and in each data block, a block address including a track number and a block number is recorded together with video data. Are numbered periodically for each fixed number of tracks, and the block numbers are numbered consecutively from the beginning of the recording track for each track. 2, it is necessary to decode the video from the reproduced partial data is compressed at a high compression rate compression method for each frame is used.
By reproducing the video data for variable-speed reproduction, variable-speed reproduction such as search and shuttle reproduction is possible even on a tape that has been recorded by performing MPEG compression.

[0003]

However, in the above-mentioned conventional system, tracks for variable-speed reproduction are limited.
At the time of variable speed reproduction, the reproducing head needs to accurately scan the center of the track for variable speed reproduction, but no specific tracking control means has been disclosed.

An object of the present invention is to provide a tracking control device and a magnetic recording / reproducing device capable of accurately tracking a predetermined track even during variable speed reproduction.

[0005]

Means for Solving the Problems To achieve the above object,
Therefore, in the present invention, a predetermined number of tracks are synchronized with the track number.
Is recorded at a predetermined position on the track with one cycle of the
Tracking control for reproducing variable playback data
The track number to extract the track number from the playback signal.
Block number extracting means for extracting a block number from a reproduced signal.
Block number extraction means and a rotating head
Desired reference scan phase when scanning obliquely over a number
Tracking deviation from the track number and block
Tracking error detection based on the
Variable speed playback at a speed faster than the normal playback speed
Tracking error of rotating head when tracking error
The control is performed using the control signal of the detecting means.

[0006]

By controlling the running of the tape so that the tracking control signal generated as described above becomes zero, the block number when the reproducing head scans the specific track matches that of the track for variable speed reproduction. As described above, the phase control is performed, and as a result, it is possible to perform tracking control such that the reproducing head accurately scans the center of the track for variable speed reproduction.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a tracking control device according to the present invention. In the figure, reference numeral 1 denotes a system control circuit for controlling the entire VTR system, 2 denotes an arithmetic circuit for outputting a block number serving as a reference for detecting a phase error, and 3 denotes a block number of a block scanned by a reproducing head. 4 is a track number extracting circuit for detecting the track number of the track being scanned by the reproducing head, and 5 is the difference between the block number from the arithmetic circuit 2 and the block number from the block number extracting circuit 3. A comparison circuit 6 for calculating, a sample and hold circuit 6 for sampling or holding the output of the block number extraction circuit 3, and a system control circuit 1 for a block number difference output from the comparison circuit 5.
Is a multiplication circuit that calculates a phase difference in the tape running direction by multiplying by a coefficient sent from the multifunction device.

The arithmetic circuit 2 uses the block number of a block to be reproduced when the reproducing head reaches a specific track when the reproducing head scans the center of the track for variable speed reproduction as a reference block number. Output to The block number extraction circuit 3 extracts the block number of the block actually scanned by the reproduction head from the reproduction signal, and outputs the extracted block number to the sample & hold circuit 6. The system control circuit 1 detects that the track number extracting circuit 4 has reached the specific track and switches the sample & hold circuit 6 to a sampling operation based on the identification signal outputted and outputs the block number extracting circuit 3. The output is output to the comparison circuit 5. The multiplying circuit 7 adds the difference between the block numbers output from the comparing circuit 5 to the system control circuit 1.
And outputs a phase error in the tape running direction.

FIG. 2 is a diagram showing an example of a recording pattern of a magnetic tape to be reproduced by a digital VTR using the tracking control device of FIG. This figure shows an example in which video data for 8 × speed reproduction in the normal direction (forward) is recorded, 21 is a magnetic tape, 22 is a reproduction head, and 23 is scanning of the reproduction head during 8 × speed reproduction. Locus, 24
Is a region where video data for normal reproduction is recorded, and a hatched portion like 25 is a portion where data for 8 × speed reproduction is recorded. At the time of 8 × speed reproduction, the reproducing head 22 scans obliquely over eight tracks like the scanning locus 23. Therefore, in order to perform the 8 × speed reproduction, the 8 × speed is set at a specific position of each of the eight tracks in accordance with the inclination of the scanning locus 23. The reproduction data 25 is divided and recorded, and these data 25 are collected to form an 8 × speed reproduction track 26. At the time of 8 × -speed playback, the playback head 22 scans the center of the track 26 for 8 × -speed playback, so that the video data 2 for 8 × -speed playback is obtained.
5 can be reproduced. In FIG. 2, 8 in the normal rotation direction
Although a double-speed recording example is shown, it is of course possible to perform recording at an arbitrary reproduction speed as needed, and recording for high-speed reproduction in a reverse direction is also possible.

FIGS. 3 and 4 are diagrams for explaining the principle of phase error detection according to the embodiment of FIG. 1. FIG. 3 shows a part of the relationship between the track on the magnetic tape of FIG. FIG. 4 shows the relationship between the track number and the block number that the reproducing head is scanning. 3, reference numerals 31, 32, and 33 denote scanning trajectories of the reproducing head, and the scanning trajectory 31 indicates a reference phase at which the reproducing head scans the center of the track 26 for variable speed reproduction shown in FIG. Between these scanning trajectories, the scanning trajectory 31 is used as a reference in the tape running direction by -2.5.
A phase difference 34 for tracks and a phase difference 35 for +0.5 tracks occur. The alphanumeric characters shown on the tracks indicate the track numbers, respectively, and the read head is track number A.
The phase difference in the longitudinal direction of the track when it reaches the track 36 is indicated by broken arrows 37 and 38, respectively.
In FIG. 4, reference numerals 41, 42, and 43 denote a relationship between a track number and a block number reproduced when the scanning trajectory of the reproducing head is 31, 32, and 33, respectively, and 41 is a reference for the relationship. Numerals 47 and 48 denote block number differences of the block numbers to be reproduced when the reproducing head reaches the track 36, based on the scanning trajectory 31.

From a graphical relationship, the phase differences 34 and 35 in the tape running direction are proportional to the phase differences 37 and 38 in the track longitudinal direction when they reach the track 36, respectively. The value is determined by the inclination of the reproduction head with respect to the track, that is, the reproduction speed of the variable speed reproduction. Further, since the absolute position in the track longitudinal direction can be detected from the block number recorded in each track, the phase difference in the track longitudinal direction can be determined by the block number to be reproduced when the reproducing head reaches the track 36 in each scanning phase. It can be calculated by detecting and detecting the number difference between the block numbers. That is, 47
And the block number difference of 48 are values proportional to the phase differences 37 and 38 in the track longitudinal direction, respectively, and the proportional coefficient is a value determined by the total number of blocks allocated in the track longitudinal direction.

From these two relationships, the scanning trajectories 32 and 3
In block 3, the block number differences 47 and 48 to be reproduced when the reproducing head reaches the track 36 are values proportional to the phase differences 34 and 35 in the tape running direction, and the proportionality coefficient indicates that the reproducing head reproduces in one track. It is the reciprocal of the number of blocks, and its value is determined from the total number of blocks in the track longitudinal direction and the number of tracks traversed by the reproducing head within one scanning period.

From such a relationship, a specific track such as the track 36 to be compared with the block number is determined, and when the reproducing head reaches the specific track on the reference scanning locus such as the scanning locus 31. The block number to be reproduced is detected as a reference block number, and the block number to be reproduced when the reproduction head actually reaches the specific track is detected as a comparison block number. By multiplying by the reciprocal of the number of blocks to be reproduced, the phase difference in the tape running direction can be calculated. This is the principle of phase error detection in this embodiment.

FIG. 5 is a diagram for explaining a method of calculating the reference block number by the arithmetic circuit 2. Reference numeral 27 denotes a scanning trajectory where the reproducing head scans the center of the track 26 for 8 × speed reproduction. The number attached to the entry side of each track indicates a track number, and the number attached to each track indicates a block number. In the figure, a track number is assigned by an eight-track completion method in which the track number is initialized every eight tracks, one track is divided into 40 blocks, and each block is sequentially numbered 1 to 40 from the scanning start position of the reproducing head. An example is shown in which block numbers up to are assigned. The video data 25 for 8 × -speed playback includes track numbers 1 to 8, block numbers 1,
6, 12, 18, 24, 29, 35, and 40.

As shown in FIG. 1, when scanning the center of the track 26 for the 8 × speed reproduction as in the scanning trajectory 27, the block number when the reproducing head crosses the track is the number specified by the track number. It turns out that it becomes. As a result, a table showing the relationship between the track number and the block number as shown in FIG. 6 can be created. This figure shows the block numbers of the blocks to be reproduced when the respective track numbers are reached at the time of 8 × speed reproduction, and such a data table is stored in the arithmetic circuit 2 for each reproduction speed. Thus, the reference block number corresponding to the reproduction speed can be output.

Hereinafter, the overall operation of the tracking control device shown in FIG. 1 will be described in the case where the reproduction speed is eight times the normal reproduction speed and the track number of the track to be compared with the block number is 4.

When a command for variable speed reproduction is issued from the system control circuit 1, the magnetic tape is raised to a predetermined tape speed at the time of 8 × speed reproduction by a control device (not shown) for controlling the tape speed. The head 22 has a trajectory 23 shown in FIG. 2 that scans over eight tracks, and then the phase control is performed so that the reproducing head scans the center of the track 26 for variable speed reproduction.

The arithmetic circuit 2 outputs the block number 16 to be reproduced when the reproducing head reaches the track of track number 4 as a reference block number to the comparing circuit 5 as shown in FIG. The extraction circuit 3 extracts the block number of the block being scanned by the reproduction head from the reproduction signal and outputs it to the sample & hold circuit 6. The system control circuit 1 detects that the track number extracting circuit 4 has reached the track of the track number 4, and switches the sample & hold circuit 6 to a sampling operation based on the identification signal output from the track number extracting circuit 4. The block number reproduced when the track 4 is reached is output to the comparison circuit 5. The comparison circuit 5 detects the difference between the two block numbers and outputs the difference to the multiplication circuit 7. The multiplication circuit 7 multiplies this by a multiplication coefficient sent from the system control circuit 1 and outputs a phase error signal in the tape running direction. This value is the reciprocal of the number of blocks reproduced by the reproducing head in one track as described above. In this embodiment, one track is composed of 40 blocks, and the reproducing head scans across eight tracks. The number of blocks to be reproduced in one track is 5, and the reciprocal of 0.2 is multiplied by the result from the comparison circuit 5. That is, since the block number difference is detected in units of one block, the phase difference in the tape running direction can be detected in units of 0.2 tracks. This phase error signal is used as a tracking control signal for speed adjustment of a capstan motor (not shown), and tracking control is performed such that the reproducing head scans the center of the track 26 for variable speed reproduction.

FIG. 7 is a block diagram showing another embodiment of the tracking control device according to the present invention. In the figure,
Numeral 8 denotes a timer counter for measuring the time from the start of scanning of the reproducing head. Numeral 9 denotes an arithmetic circuit for calculating a reference time used as a reference for detecting a phase error. Other parts denoted by the same reference numerals as those in FIG. And the operation is also the same. The recording pattern of the magnetic tape reproduced by the digital VTR using the tracking control device according to the embodiment of FIG. 7 is the same as that of FIG.

The arithmetic circuit 9 stores the relationship between the track number and the head scanning time when the reproducing head scans the center of the track for variable speed reproduction as a data table corresponding to the reproducing speed. The head scanning time when the number is reached is output as a reference time to the comparison circuit. The timer counter 8 is a counter for measuring time by performing measurement with a fixed clock, and is cleared by the timing of the start of scanning of the reproducing head, for example, the rising and falling signals of the head switching signal, and measures the scanning time of the reproducing head. . The output of the timer counter 8 to the comparison circuit 5 is controlled by the configuration of the system control circuit 1, the track number extraction circuit 4 and the sample & hold circuit 6, and is sampled when the reproduction head reaches the specific track, and is compared. Output to the circuit 5.

FIGS. 8 and 9 are views for explaining the principle of the phase error detection according to the present embodiment. FIG. 8 shows a part of the relationship between the track on the magnetic tape and the scanning locus of the reproducing head in FIG. FIG. 9 shows the relationship between the track number of the track being scanned by the reproducing head and the time from the start of scanning of the reproducing head. 8, 51, 5
Reference numerals 2 and 53 denote scanning trajectories of the reproducing head.
Reference numeral 1 denotes a reference phase at which the reproducing head scans the center of the track 26 for variable speed reproduction shown in FIG. 3, the phase difference 54 for the -2.5 track and the phase difference 55 for the +0.5 track in the tape running direction with respect to the scanning trajectory 51 as in the case of FIG.
Shows a state in which is occurring. The alphanumeric characters shown on the track indicate the track number, and the playback head is track number A.
The time from the start of scanning by the reproducing head when the track 56 is reached is indicated by broken-line arrows 57, 58 and 59, respectively, and 57 indicates a reference time in the present embodiment. In FIG. 9, reference numerals 61, 62 and 63 denote the relationship between the track number reproduced when the scanning trajectory of the reproducing head is 51, 52 and 53, and the head scanning time, and 61 is a reference for the relationship. is there. Also, 6
7, 68 and 69 indicate head scanning times when the reproducing head reaches the track 56, similarly to 57, 58 and 59, respectively.

The time from the start of scanning of the reproducing head to the scanning of the track 56 is different for each of the scanning phases 51, 52 and 53, and the time is a time difference proportional to the phase difference in the tape running direction. Has occurred. Specifically, assuming that the time when the reproducing head crosses one track during variable speed reproduction is T, the reference time is 57 with respect to 57.
8 and 59, between -2.5 × T and +0.
There is a time difference of 5 × T. Coefficient 1
/ T is multiplied by the phase difference 54 in the tape running direction.
And 55 can be calculated.

From such a relationship, a track such as the track 56 for comparing the head scanning time is determined, and the head until the reproducing head reaches the specific track on the reference scanning trajectory such as the scanning trajectory 51 is determined. By detecting the scanning time as the reference head scanning time and the head scanning time when the reproducing head actually reaches the specific track as the comparison head scanning time, and multiplying the time difference between the two head scanning times by 1 / T. , The phase difference in the tape running direction can be calculated. This is the principle of phase error detection in the present embodiment.

The reference head scanning time is shown in FIG.
By storing the data table as a data table corresponding to the reproduction speed in the same manner as in the embodiment, it is possible to output from the arithmetic circuit 9 the reference head scanning time when reaching the specific track.

A description will now be given of the entire operation of the tracking control device shown in FIG. 7 in the case where the reproduction speed is eight times the normal reproduction speed and the track for comparing the head scanning time is the track 56 in FIG.

When a command for variable speed reproduction is issued from the system control circuit 1, a magnetic tape is started up to a tape speed of 8 × speed reproduction by a control device (not shown) for controlling the tape speed. Phase control is performed so that the scanning of the center 22 of the track 26 for variable speed reproduction is performed.

The arithmetic circuit 9 compares the head scanning time 67 when the reproducing head reaches the track 56 as the reference head scanning time based on the relationship between the reference head scanning time and the track number as indicated by 61 in FIG. Output to the circuit 5. Further, the system control circuit 1 controls the sample and hold circuit 6 to perform a sampling operation based on the track number extracting circuit 4 which detects the track number A, that is, the identification signal outputted by detecting that the reproducing head has reached the track 56. Then, the comparison circuit 5 calculates the time difference between the reference head scanning time 67 from the arithmetic circuit 9 and the actual head scanning time from the timer counter 8 and outputs the result to the multiplication circuit 7.
The time difference is converted into a tracking error signal in the tape running direction by the multiplying circuit 7, and is used for the tracking error signal in FIG.
As in the embodiment, tracking control is performed such that the reproducing head scans the center of the track for variable speed reproduction.

The embodiment of the present invention has been described above. In the embodiment of FIGS. 1 and 7, variable speed reproduction in the forward direction is taken as an example. However, the present invention is not particularly limited to this, and is also applicable to variable speed reproduction in the reverse direction. Of course, it can be expanded similarly. Also, the variable speed reproduction speed has been described as an example of the 8 × speed, but this is not particularly limited, and it is needless to say that the variable speed reproduction at an arbitrary speed can be performed as needed. further,
In the present embodiment, the track for comparing the block number and the head scanning time is fixed to one specific track. However, this is not particularly limited, and the tracking control signal is generated in a plurality of tracks as necessary. Various modifications can be easily made without departing from the spirit of the present invention.

Further, the description of this embodiment has been limited to the case where the track pattern for variable speed reproduction is as shown in FIG. 2. For example, video data for variable speed reproduction is recorded in the longitudinal direction of the tape. In this case, it is not necessary to determine a specific track, and a tracking control signal may be generated similarly by detecting a reproduction block number or a head scanning time at a switching point of a track number and comparing the detected value with a reference value. It is possible.

[0031]

As described above, according to the present invention, at the time of variable speed reproduction, when the reproduction head scans the center of the track for variable speed reproduction, when the reproduction head reaches a specific track, reproduction is performed. Based on the block number
A reproducing head for generating a tracking control signal corresponding to a number difference from a block number to be reproduced when actually arriving at the specific track, or when the reproducing head scans the center of a track for variable speed reproduction. Generates a tracking control signal corresponding to a time difference from the head scanning time when the head actually reaches the specific track based on the head scanning time when the head arrives at the specific track. A control signal can be generated, and tracking control can be performed so that the reproducing head accurately scans the center of the track for variable speed reproduction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing a recording pattern on a magnetic tape to be reproduced in the embodiment of FIG.

FIG. 3 is a diagram showing recording tracks on a magnetic tape to be reproduced in the embodiment of FIG. 1 and scanning loci of a reproducing head;

FIG. 4 is a diagram showing a relationship between a track number and a block number in FIG. 3;

FIG. 5 is a diagram illustrating the operation of the arithmetic circuit in FIG.

FIG. 6 is a diagram showing a relationship between a track number and a block number in FIG. 5;

FIG. 7 is a configuration diagram showing one embodiment of the present invention.

8 is a diagram showing a recording track on a magnetic tape to be reproduced in the embodiment of FIG. 7 and a scanning locus of a reproducing head.

FIG. 9 is a diagram showing a relationship between a track number and a head scanning time in FIG. 8;

FIG. 10 is a diagram showing a recording pattern on a magnetic tape to be reproduced by a conventional digital VTR.

[Explanation of symbols]

1 ... System control circuit, 2 ... Operation circuit, 3 ...
.Block number extraction circuit, 4... Track number extraction circuit,
5 ... Comparison circuit, 6 ... Sample & hold circuit, 7 ...
Multiplying circuit, 8: Timer counter, 9: Arithmetic circuit 21: Magnetic tape, 22: Reproducing head, 23: Scanning locus of the reproducing head during 8 × speed reproduction, 24: Normal Video data for playback, 25... Video data for 8 × speed playback, 2
6 ... 8x speed playback track

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-251459 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 15/467

Claims (5)

(57) [Claims] A tape on which a track on which a main information signal digitized and a track number and a block number identification information signal are recorded in each block is divided into a plurality of data blocks. A tracking control device for reproducing variable reproduction data recorded at a predetermined position on a track with a predetermined number of tracks as one cycle in synchronization with the track number when reproducing by the helical scan method, Reproducing means for reproducing the identification information signal from a tape; track number extracting means for extracting the track number from the reproduced signal; block number extracting means for extracting the block number from the reproduced signal; When scanning obliquely over a plurality, the tracking deviation with respect to the desired reference scanning phase A tracking error detecting means for detecting the track number and the block number on the basis of an extraction result, and performing a tracking control of the rotary head during variable speed reproduction at a speed higher than a normal reproduction speed by using a control signal of the tracking error detecting means. A tracking control device, characterized in that the tracking control device performs the tracking control. 2. The data processing apparatus according to claim 1, wherein the tracking error detecting means has a relation between a track number corresponding to a desired reference scanning phase of the rotary head and a reference time from the start of scanning of the rotary head required for reproducing the track number in a data table. An arithmetic circuit for calculating and outputting, as a reference time, a time required for the rotary head to scan a track of a specific number based on the data table; a track number reproduced in the actual scan of the rotary head; A time measuring means for detecting a required time and outputting a required time when a track of a specific number is scanned as a comparison time; and comparing a reference time which is an output of the arithmetic circuit with a comparison time which is an output of the time measuring means. And a comparing means for generating a tracking error signal corresponding to the time difference. 2. The tracking control device according to claim 1, wherein the tracking control is performed on the same specific track at more than one place. 3. The tracking error detecting means has information on a block number at a switching point of a track number corresponding to a desired reference scanning phase of the rotary head in a data table, and when the track number is switched based on the data table. A calculation circuit for calculating and outputting a block number to be reproduced as a reference block number, a track number and a block number to be reproduced by actual scanning of the rotary head, and a block number to be reproduced when the track number is switched. A block number detecting means for outputting a reference block number as an output of the arithmetic circuit and a comparison block number as an output of the block number detecting means.
2. A comparison means for generating a tracking error signal according to a block number difference, wherein the tracking error signal is detected at at least one or more track number switching points. Tracking control device. 4. The tracking error detecting means has information on time from the start of scanning of the rotary head at a switching point of a track number corresponding to a desired reference scanning phase of the rotary head in a data table, and based on the data table. An arithmetic circuit for calculating and outputting the time from the start of scanning of the rotary head when the track number is switched as a reference time, and detecting the track number reproduced by the actual scanning of the rotary head and the required time from the start of scanning of the rotary head. And a time measuring means for outputting the required time when the track number is switched as a comparison time, and comparing the reference time, which is the output of the arithmetic circuit, with the comparison time, which is the output of the time measuring means, according to the time difference. Comparing means for generating a tracking error signal, and detecting at least one tracking error signal. 2. The tracking control device according to claim 1, wherein the tracking control is performed at more than one switching point of the track number. 5. A helical scan system having a rotating head, wherein each track on a tape is divided into a plurality of data blocks, and a main information signal digitized in each block, and track number and block number identification information. A magnetic recording / reproducing apparatus for recording and reproducing signals, a recording means for recording the main information signal and the identification information signal on a tape by the rotary head, and a reproduction for reproducing the main information signal and the identification information signal from the tape Means, a track number extracting means for extracting the track number from the reproduced signal, a block number extracting means for extracting the block number from the reproduced signal, and a predetermined number of tracks as one cycle in synchronization with the track number. Tracking control means for reproducing the variable reproduction data recorded at a predetermined position of When the rotary head scans the track obliquely over a plurality of tracks, the head includes tracking error detection means for detecting a tracking shift with respect to a desired reference scanning phase based on the track number and block number extraction results. A magnetic recording / reproducing apparatus, wherein tracking control of the rotary head during variable speed reproduction at a speed higher than the speed is performed using a control signal of the tracking error detecting means.