JPH0896451A - Tracking control device - Google Patents

Abstract

PURPOSE: To exactly track a specified track by generating a tracking control signal corresponding to the difference between the number of the reference block and that of the block to be compared and controlling tracking at the time of variable-speed reproduction. CONSTITUTION: The arithmetic circuit 2 outputs the block number of the block which the reproducing head reproduces when it reaches a specified track in the case where the reproducing head scans the center of the track for variable- speed reproduction to the comparison circuit 5 as a reference block number. Based on the identification number which the track number extraction circuit 4 detects that the specified track is reached and outputs, the system control circuit 1 switches the sample-and-hold circuit 6 to sampling action to output the output of the block number extraction circuit 5 to the comparison circuit 5. The multiplication circuit 7 multiplies the difference between the block number and the reference number outputted from the comparison circuit 5 by the factor sent from the system control circuit 1 to output the phase error in the tape running direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a consumer digital VT.
The present invention relates to a tracking control device in variable speed reproduction of R.

[0002]

2. Description of the Related Art A consumer digital VTR utilizes an image compression technique such as an MPEG system to reduce the amount of data recorded on a magnetic tape. In the MPEG system,
Since the video is constructed using the differences between the frames,
When variable speed reproduction or the like is performed, the continuity of the data of the preceding and succeeding frames is lost, and thus it is not possible to reconstruct the video from the reproduced data. Therefore, as a variable speed reproduction method of a digital VTR using the MPEG method 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) "has been proposed. This method, as shown in FIG. 10, enables a reproducing head so that an image can be decoded even at a variable speed reproduction. The variable-speed reproduction video data 72 is recorded separately from the normal-reproduction video data 24 at a specific position on the magnetic tape 21 in accordance with the scanning locus 71 of 22 to form a variable-speed reproduction track 73. Each track is composed of a plurality of data blocks of about several hundred bytes, and each data block records a track number and a block address including the block number together with video data. Are periodically numbered every fixed number of tracks, and the block numbers are consecutive numbers 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 these video data for variable speed reproduction, variable speed reproduction such as search or shuttle reproduction is possible even on a tape recorded by MPEG compression.

[0003]

However, in the above-mentioned conventional method, since the 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 capable of accurately tracking a predetermined track even during variable speed reproduction.

[0005]

An arithmetic circuit for outputting a block number to be reproduced when reaching a specific track as a reference block number when the reproducing head scans the center of a track for variable speed reproduction, and a reproducing head. Is provided with block number detecting means for detecting a block number to be reproduced when the track actually reaches the specific track as a comparison block number, and generates a tracking control signal according to the number difference between the reference block number and the comparison block number. , Tracking control during variable speed playback was performed.

[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 a specific track matches that of the variable speed reproducing track. Thus, the phase control is performed, and as a result, the tracking control can be performed so 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, 1 is a system control circuit for controlling the entire VTR system, 2 is an arithmetic circuit for outputting a block number serving as a reference for phase error detection, and 3 is a block number of a block scanned by a reproducing head. A block number extraction circuit 4, a track number extraction circuit for detecting the track number of the track being scanned by the reproducing head, and 5 a difference between the block numbers from the arithmetic circuit 2 and the block number extraction circuit 3. A comparison circuit for calculation, 6 is a sample & hold circuit for sampling or holding the output of the block number extraction circuit 3, and 7 is a system control circuit 1 for the block number difference output from the comparison circuit 5.
This is a multiplication circuit that calculates the phase difference in the tape running direction by multiplying by the coefficient sent from.

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

FIG. 2 is a diagram showing an example of a recording pattern of a magnetic tape which is 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 forward direction is recorded. Reference numeral 21 is a magnetic tape, 22 is a reproducing head, and 23 is scanning of the reproducing head during 8 × speed reproduction. Trajectory, 24
The blank portion of is a region in which video data for normal reproduction is recorded, and the shaded portion such as 25 is a portion in which data for 8-times speed reproduction is recorded. During the 8 × speed reproduction, the reproducing head 22 scans diagonally over 8 tracks like the scanning locus 23. Therefore, in order to perform the 8 × speed reproduction, the 8 × speed is set at a specific position on each of the 8 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 a track 26 for octuple speed reproduction. During 8x speed reproduction, the reproducing head 22 scans the center of the track 26 for 8x speed reproduction so that the video data 2 for 8x speed reproduction is obtained.
5 can be reproduced. In Fig. 2, 8
Although an example of double-speed recording is shown, it is of course possible to perform recording according to an arbitrary reproduction speed as necessary, and recording for high-speed reproduction in the reverse direction is also possible.

3 and 4 are diagrams for explaining the principle of phase error detection according to the embodiment of FIG. 1, and FIG. 3 shows a part of the relationship between the tracks on the magnetic tape of FIG. 2 and the scanning locus of the reproducing head. FIG. 4 shows the relationship between the track number scanned by the reproducing head and the block number. In FIG. 3, reference numerals 31, 32, and 33 are scanning loci of the reproducing head, and the scanning locus 31 shows a reference phase with which the reproducing head scans the center of the track 26 for variable speed reproduction shown in FIG. Between these scanning loci, the scanning locus 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 in the track indicate the track number, respectively, and the playback head is track number A.
The phase difference in the track longitudinal direction when reaching the track 36 is shown by broken line arrows 37 and 38, respectively.
In FIG. 4, reference numerals 41, 42 and 43 denote the relationship between the track number and the block number which are reproduced when the scanning loci of the reproducing head are 31, 32 and 33, respectively, and 41 is the reference for the relationship. Reference numerals 47 and 48 show the difference between the block numbers of the block to be reproduced when the reproducing head reaches the track 36, based on the scanning locus 31.

From the graphical relationship, the phase differences 34 and 35 in the tape running direction have a proportional relationship with the phase differences 37 and 38 in the track longitudinal direction when reaching the track 36, respectively, and the proportional coefficient is The value is determined by the tilt of the reproducing head with respect to the track, that is, the reproducing speed of variable speed reproduction. As for the phase difference in the track longitudinal direction, since the absolute position in the track longitudinal direction can be detected from the block number recorded in each track, the block number to be reproduced when the reproducing head reaches the track 36 in each scanning phase is set. It can be calculated by detecting and detecting the difference in the block numbers. That is, 47
And the block number differences of 48 are 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, scanning trajectories 32 and 3
The block number differences 47 and 48 reproduced when the reproducing head reaches the track 36 in 3 are values proportional to the phase differences 34 and 35 in the tape running direction, and the proportional coefficient reproduces in one track by the reproducing head. It is the reciprocal of the number of blocks, and its value is obtained from the total number of blocks in the track longitudinal direction and the number of tracks that the reproducing head crosses within one scanning period.

From such a relationship, a specific track such as the track 36 for comparing block numbers is determined, and when the reproducing head reaches the specific track on the reference scanning locus such as the scanning locus 31. The playback block number is detected as the reference block number, and the playback block number when the playback head actually reaches the specific track is detected as the comparison block number. The phase difference in the tape running direction can be calculated by multiplying it by the reciprocal of the number of blocks to be reproduced. 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, and 27 shows a scanning locus in which the reproducing head scans the center of the track 26 for octuple speed reproduction. Also, the numbers attached to the entry sides of the respective tracks indicate the track numbers, and the numbers attached on the respective tracks indicate the block numbers. In the figure, the track number is added by a method of completing 8 tracks, which is initialized every 8 tracks, and one track is divided into 40 blocks, and each block is sequentially arranged from 1 to 40 from the scanning start position of the reproducing head. The block numbers up to are shown as an example. The video data 25 for 8 × speed reproduction has the block number 1 and the track number 1 to 8 respectively.
It is recorded in blocks 6, 12, 18, 24, 29, 35, and 40.

As shown in the figure, the block number when the reproducing head crosses the track while scanning the center of the track 26 for 8-times speed reproduction as shown by the scanning locus 27 is specified by the track number. You can see that. From this, a table showing the relationship between track numbers and block numbers 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 during octuple speed reproduction, and such a data table is stored in the arithmetic circuit 2 for each reproduction speed. As a result, the reference block number corresponding to the reproduction speed can be output.

Hereinafter, the entire operation of the tracking control device of FIG. 1 will be described in the case where the reproduction speed is 8 times the normal reproduction speed and the track number of the track to be compared is 4.

When a command for variable speed reproduction is issued from the system control circuit 1, the control device (not shown) for controlling the tape speed raises the magnetic tape to a predetermined tape speed at the time of 8-times speed reproduction and reproduces it. The head 22 has a locus such as 23 shown in FIG. 2 which scans over 8 tracks, and then phase control is performed so that the reproducing head scans the center of the track 26 for variable speed reproduction.

As shown in FIG. 6, the arithmetic circuit 2 outputs 16 as the reference block number, which is the block number to be reproduced when the reproducing head reaches the track of track number 4, to the comparing circuit 5, and outputs the block number. The extraction circuit 3 extracts the block number of the block scanned by the reproduction head from the reproduction signal and outputs it to the sample & hold circuit 6. The system control circuit 1 switches the sample & hold circuit 6 to the sampling operation based on the identification signal output when the track number extraction circuit 4 detects that the track number 4 has been reached and outputs the track number. The block number reproduced when the track No. 4 is reached is output to the comparison circuit 5. The comparison circuit 5 detects the difference between the two block numbers and outputs it to the multiplication circuit 7. The multiplication circuit 7 multiplies this by the multiplication coefficient sent from the system control circuit 1 to output 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 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 so 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,
Reference numeral 8 is a timer counter for measuring the time from the start of scanning of the reproducing head, 9 is an arithmetic circuit for calculating a reference time which serves as a reference for phase error detection, and other parts denoted by the same reference numerals as those in FIG. 1 are the same or equivalent. , And the operation is also the same. The recording pattern of the magnetic tape reproduced by the digital VTR using the tracking controller 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 according to the reproducing speed, and the specific track The head scanning time when the number is reached is output to the comparison circuit as the reference time. The timer counter 8 is a time measuring counter that measures with a fixed clock, and is cleared at the timing of the scanning start of the reproducing head, for example, the rising and falling signals of the head switching signal, and the scanning time of the reproducing head is measured. . 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 reproducing head reaches the above-mentioned specific track for comparison. It is output to the circuit 5.

8 and 9 are views for explaining the principle of phase error detection according to the present embodiment. FIG. 8 is a part of the relationship between the tracks on the magnetic tape and the scanning track of the reproducing head shown 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 by the reproducing head. In FIG. 8, 51 and 5
Reference numerals 2 and 53 are the scanning loci of the reproducing head, and the scanning locus 5
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. Between these scanning loci, with reference to the scanning locus 51, as in the case of FIG. 3, a phase difference 54 of −2.5 tracks and a phase difference 55 of +0.5 tracks in the tape running direction, respectively.
Shows the state where is occurring. The alphanumeric characters shown on the track indicate the track number, and the playback head indicates track number
The time from the start of scanning of the reproducing head when the track 56 is reached is indicated by the dashed arrows 57, 58, and 59, respectively, and 57 indicates the reference time in this embodiment. In FIG. 9, reference numerals 61, 62 and 63 indicate the relationship between the track number reproduced when the reproducing head scanning loci are 51, 52 and 53 and the head scanning time, and 61 is the reference of the relationship. is there. Also, 6
Similar to 57, 58 and 59, 7, 68 and 69 respectively indicate the head scanning time when the reproducing head reaches the track 56.

The time from the start of scanning 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, when the time taken for the reproducing head to cross one track during variable speed reproduction is T, it is 5 with respect to the reference time of 57.
Between 8 and 59 are -2.5 * T and +0.
There is a time difference of 5 × T. Coefficient 1 for this time difference
By multiplying / T, the phase difference in the tape running direction is 54
And 55 can be calculated.

From such a relationship, a track such as the track 56 to which head scanning times are compared is determined, and a reproducing head reaches a specific track on a reference scanning locus such as the scanning locus 51. 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 comparative head scanning time, and multiplying the time difference between both 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 this embodiment.

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

The operation of the entire tracking control device shown in FIG. 7 will be described below assuming that the reproduction speed is eight times the normal reproduction speed and the track for comparing head scanning times is the track 56 in FIG.

When a command for variable speed reproduction is issued from the system control circuit 1, the controller (not shown) for controlling the tape speed causes the magnetic tape to rise to the tape speed for octuple speed reproduction, and then the reproducing head. Phase control is performed so that 22 scans the center of the track 26 for variable speed reproduction.

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 & hold circuit 6 to perform a sampling operation on the basis of the identification signal output by the track number extraction circuit 4 upon detecting the track number A, that is, when the reproducing head has reached the track 56 and outputting it. 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 it to the multiplication circuit 7.
Then, this time difference is converted into a tracking error signal in the tape traveling direction by the multiplication circuit 7, and this is used to calculate the tracking error signal in FIG.
Similar to the above embodiment, tracking control is performed so that the reproducing head scans the center of the track for variable speed reproduction.

The embodiments of the present invention have been described above. In the embodiments of FIGS. 1 and 7, the variable speed reproduction in the forward direction is taken as an example, but this is not particularly limited, and it is also applicable to the variable speed reproduction in the reverse direction. Of course, it can be expanded in the same way. Although the variable speed reproduction speed is set to 8 times as an example, the variable speed reproduction speed is not particularly limited, and it is needless to say that variable speed reproduction at an arbitrary speed can be performed. further,
In the present embodiment, the track for comparing the block number and the head scanning time is fixed to one specific track, but this is not particularly limited, and a tracking control signal is generated in a plurality of tracks as necessary. It is also possible to make various modifications without departing from the spirit of the present invention.

Further, although the description of the present embodiment is 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 tape longitudinal direction. In this case, it is not necessary to define a specific track, and a tracking control signal may be similarly generated by detecting the reproduction block number at the track number switching point or the head scanning time and comparing it with a reference value. It is possible.

[0031]

As described above, according to the present invention, during variable speed reproduction, when the reproducing head scans the center of the track for variable speed reproduction, reproduction is performed when the reproducing head reaches a specific track. Based on the block number to
When the reproducing head actually generates the tracking control signal according to the number difference from the block number to be reproduced when reaching the specific track, or when the reproducing head scans the center of the track for variable speed reproduction. Since a tracking control signal is generated according to the time difference from the head scanning time when actually reaching the specific track, the tracking control signal is generated based on the head scanning time when reaching the specific track. A control signal can be generated, and tracking control in which the reproducing head accurately scans the center of the track for variable speed reproduction is possible.

[Brief description of drawings]

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

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

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

FIG. 4 is a diagram showing a relationship between track numbers and block numbers in FIG.

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

FIG. 6 is a diagram showing a relationship between track numbers and block numbers in FIG.

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

FIG. 8 is a diagram showing recording tracks on a magnetic tape reproduced in the embodiment of FIG. 7 and scanning loci of a reproducing head.

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

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

[Explanation of symbols]

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

Claims (5)

[Claims] 1. A helical scan system having a rotary head, wherein each track on a tape is divided into a plurality of data blocks, and a main information signal digitized into each block and identification information of a track number and a block number. In a magnetic recording / reproducing apparatus that records and reproduces a signal, a tracking deviation with respect to a desired reference scanning phase when the rotary head obliquely scans the tracks based on the reading result of the identification information signal. A tracking error detecting means for detecting, wherein the tracking control of the rotary head at the time of variable speed reproduction of an arbitrary speed higher than the normal reproduction speed is performed by using a control signal of the tracking error detecting means. Control device. 2. The tracking error detecting means has a relationship between a track number and a block number corresponding to a desired reference scanning phase of the rotary head in a data table, and the rotary head identifies a track of a specific number based on the data table. An arithmetic circuit for arithmetically outputting the block number to be reproduced as a reference when scanning, and a track number and a block number reproduced by the actual scanning of the rotary head are detected, and when a track of a specific number is scanned. A block number detecting means for outputting the reproduced block number as a comparison block number, a reference block number output by the arithmetic circuit and a comparison block number output by 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 in at least one and the same specific track. Tracking control device. 3. The tracking error detecting means has a data table having 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 to reproduce the track number. An arithmetic circuit for arithmetically outputting the time required for the rotary head to scan a track of a specific number on the basis of the data table as a reference time, and a track number reproduced by actual scanning of the rotary head and the start of scanning of the rotary head. A time measuring unit that detects the required time and outputs the required time when scanning a track of a specific number as a comparison time, and a reference time that is the output of the arithmetic circuit and a comparison time that is the output of the time measuring unit. And a comparator for generating a tracking error signal according to the time difference, and at least one of the tracking error signals is detected. The tracking control device according to claim 1, wherein the tracking control device is performed at the same specific track at more than one place. 4. The tracking error detecting means has information of a block number at a switching point of track numbers 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. An arithmetic circuit for arithmetically outputting a block number to be reproduced as a reference block number, and a block number reproduced when the track number is switched by detecting the track number and the block number reproduced by the actual scanning of the rotary head. Block number detecting means for outputting as a comparison block number, comparing a reference block number output by the arithmetic circuit with a comparison block number output by the block number detecting means,
A comparison means for generating a tracking error signal according to a block number difference, and the tracking error signal is detected at at least one switching point of the track numbers. The tracking control device described. 5. The tracking error detection means has information on time from the start of scanning of the rotary head at a switching point of track numbers corresponding to a desired reference scan phase of the rotary head in a data table, and based on the data table. An arithmetic circuit for arithmetically outputting the time from the scanning start of the rotary head when the track number is switched to the reference time, and the track number reproduced by the actual scanning of the rotary head and the time required from the scanning start of the rotary head are detected. Then, the time measuring means for outputting the required time when the track number is switched as the comparison time is compared with the reference time which is the output of the arithmetic circuit and the comparison time which is the output of the time measuring means. 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 device is performed at the switching points of the track numbers above and below.