JPH033308B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a rotary head type reproducing device.

A VTR (video tape recorder) is well known as a rotary head type playback device. conventional VTR
Now, for high-density recording, the track width is set to several tens of μm.
m or less, reproducing a control signal recorded in the longitudinal direction of the side edge of the magnetic tape together with the recording signal, and controlling the rotation of the rotary head and the capstan by this control signal,
A tracking servo is applied so that the scanning locus of the head during reproduction matches the recording track.
In addition, in high-end VTRs, the rotary head is configured to be movable not only by control signals but also by a piezoelectric element, and changes in the envelope of the reproduced signal obtained by wobbling the rotary head, or changes between several recording tracks. The rotary head is moved by the crosstalk components of the pilot signals, which have different frequencies, to ensure correct tracking.

Further, as a prerequisite for performing regular tracking, it is necessary that the tape running path including the tape guide drum has high mechanical precision and that the tape guide drum has high hardness.

These high-precision tracking servos, high machining precision, etc. are obstacles to lowering the cost of rotary head type playback devices.

The object of the present invention is to realize a rotary head type reproducing device that eliminates the need for high-precision machining, high-hardness cylinders, high-precision servos, etc. required for tracking. Furthermore, the present invention focuses on the fact that, unlike analog information signals, even when digital information signals are made continuous, the joints do not become discontinuous.
It is an object of the present invention to provide a rotary head type device for reproducing digital information signals.

An embodiment in which the present invention is applied to a device having one rotating head will be described below. In FIG. 1, 1a and 1b indicate an upper drum and a lower drum, respectively, for guiding the magnetic tape, and a rotary head 2 slightly protrudes from the gap between the two drums, and extends 360° around the circumferential surfaces of the drums 1a and 1b. The magnetic tape 3 traveling in a diagonally wound state is brought into sliding contact with the rotary head 2. The magnetic tape 3 has an inclined recording track as shown in FIG.
Tn _-1 , Tn, Tn ₊₁ , ... are formed sequentially. In this example, the track width Wt of recording tracks Tn _-1 , Tn, Tn _{+1 .} . . and the guard band width Wg between adjacent tracks are selected to be equal.

In FIG. 3, an analog signal to be recorded, such as an audio signal, is supplied to an input terminal indicated by 4,
The A/D converter 5 converts the signal into an audio PCM signal. This audio PCM signal is supplied to the encoder 6, where a synchronization signal, error correction code, and error detection code are added. FIG. 4 shows the code structure of recording data obtained from the output of the encoder 6. A synchronization signal, a block address signal, and a CRC code for error detection are added to data consisting of a plurality of samples of audio PCM signals or error correction codes. The error correction code is
Parity codes, adjacent codes, etc. may be used, and interleaving may also be used. The block address signal is as described below.
This is used to individually distinguish blocks in a series of playback data input to the TBC memory, and can use simple incremental code signals, combinations of multiple types of addresses, etc.
The CRC code is designed to detect the presence or absence of errors in both the block address signal and data.

The output of the encoder 6 is supplied to a modulator 7 and converted into a code state suitable for recording and reproduction.
Various modulation methods such as NRZI, 3PM, MFM, etc. can be used. A recording signal obtained from the output of the modulator 7 is supplied to the rotary head 2 via a recording amplifier 8, a recording side terminal 10r of a recording/reproducing switch 9, and a rotary transformer (not shown).

During reproduction, the rotational speed of the rotary head 2 is set to be higher, for example twice, than during recording. In other words, the rotary head 2 scans the magnetic tape 3 twice while the magnetic tape 3 is fed one track. In this way, since the number of scans during playback is larger than the number of scans during recording, the playback scan locus pitch is smaller than the track pitch, and even if no tracking is performed, each of all recorded tracks can be scanned one line at a time. The above-described reproduction scanning locus will necessarily pass.

The playback output of the rotary head 2 is taken out to the playback side terminal 10p of the recording/playback switch 9, and is sent to the playback amplifier 11.
is supplied to the detector 12 via. The detector 12 shapes the waveform of the reproduced signal into a pulse signal. The output of this detector 12 is supplied to a clock extraction circuit 13, and a clock pulse synchronized with the reproduced data is extracted. The output of this clock extraction circuit 13 is supplied to a demodulation circuit 14, and reproduced data having the same code structure as the recorded data is obtained.

This reproduced data is supplied to a delay circuit 15, a synchronous separation circuit 16, and a CRC checker 17. CRC
The checker 17 uses a synchronization signal to detect the presence or absence of errors in each block of reproduced data and block address signals using a CRC code.
An error flag indicating the presence or absence of an error is generated for each block in the output. The error flag becomes "1" when an error is detected, and becomes "0" when no error is detected. The delay circuit 15 delays the reproduced data and block address signal by the time required for error detection by the CRC checker 17.

The above-mentioned playback data, block address signal, and error flag are processed by the time base collector (hereinafter referred to as
(abbreviated as TBC) 18. TBC18
consists of a memory (RAM) and its peripheral circuits.Basically, the reproduced data is written to the memory by a clock synchronized with the reproduced data, and the memory is written by a reference clock from the timing generation circuit 19. The system is configured to continuously output data from the beginning and remove time axis fluctuations. Writing to the memory of the TBC 18 is performed using an address based on a block address signal, and writing of data determined to have an error by the error flag is prohibited. As mentioned above, the error flag indicates not only the data but also the presence or absence of an error in the block address signal, so when there is an error, writing is prohibited to prevent writing to the wrong address. be done. Also, if writing is prohibited, previously written data remains at the corresponding address, so in order to prevent this from being read as correct data, it is necessary to ensure that the data at that address is error data. Writes an error flag indicating. This error flag is written immediately after reading correct data. Reading of the memory of the TBC 18 is performed sequentially in a predetermined order, and a data series and an error flag indicating the presence or absence of an error for each block are obtained as output and supplied to the decoder 20.

The decoder 20 corrects data determined to have an error using an error correction code, and performs correction by replacing uncorrectable data with interpolated data. The interpolated data is, for example, the average value of correct data located before and after. Output data from this decoder 20 is supplied to a D/A converter 21, and a reproduced audio signal is taken out at an output terminal 22.

In one embodiment of the invention described above, the track width
Since Wt and the guard band width Wg are equal and the number of scans during reproduction is twice the number of scans during recording, the recording tracks Tn _-1 , Tn, Tn ₊₁ and the reproduction scan trajectories N ₁ , N ² , N ₃ , N ₄ and N ₅ are shown in Figure 5A.
It will be as shown below. When the rotary head 2 first scans in the direction of the arrow, a scanning locus _N1 passing through the recording tracks Tn ^- ₁ and Tn is drawn, and the reproduced signal shown in FIG. 5B is generated.
S ₁ is obtained. The reproduced signal has an envelope that is approximately proportional to the area of the region where the recording track and the scanning locus overlap. Below, the second scanning trajectory N ₂ ,
Every time the third scanning trajectory N ₃ and the fourth scanning trajectory N ₄ are drawn, reproduction signals S ₂ , S ₃ , and S ₄ are generated in sequence. Focusing on the recording track Tn, the reproduction output from this recording track Tn is as shown by the solid line in FIG. 5B. The envelopes of the reproduced signals S ₁ and S ₃ reach their maximum values at the timings of t ₂ and t ₄ , and the envelopes of the reproduced signals S ₂ and S ₄ reach their maximum values at the timings of t ₁ and t ₃ . Such a playback signal
S ₁ to _{S 4} are supplied to the above-mentioned reproduction system and processed, but when the level of the reproduction signals S ₁ to _{S 4} falls below a predetermined value, for example, 1/3 of the maximum value, the S/N deteriorates. , the waveform may not be shaped correctly by the detector 12. Therefore, the reproduced signals S ₁ to S ₄ and the corresponding reproduced data DT ₁ to _{DT 4} have invalid data sections (indicated by cross marks) intermittently, as shown in FIG. 5C. . However, regarding the recording track Tn of interest, the data obtained in the interval t ₃ to _{t 4} in the reproduced signal S ₁ and the interval t ₃ to t ₄ in the reproduced signal S ₂ are the same. Similarly, the data obtained in the interval t ₂ to _{t 3} in the reproduced signal S ₂ and the interval t 2 to t 3 in the reproduced signal S ₃ , the interval t ₁ to _{t 2} in the reproduced signal S 3, and the data obtained in the interval t ₂ to _{t 3} in the reproduced signal S ₃ t ₁ to _{t 2} in signal S ₄
Each of the data obtained in the interval is the same. Due to this duplication of playback data, even if the playback data includes an invalid data section, the data in that part will be played back in the next scan, so there will be no problem. . In addition, in FIG. 5C, the shaded area indicates the recording track.
It shows the interval where the same data is obtained overlappingly among Tn data. Of course, the recording track Tn
The reproduction data of other recording tracks is also the same as described above.

In this way, while a single recording track records the original audio PCM signal or the audio PCM signal whose arrangement is regularly changed by interleaving, the time series of the reproduced data is It will be different from when it was recorded. However, when writing playback data to the memory of the TBC 18 as described above, writing is performed at an address determined by the block address signal added to each block of playback data, and reading is performed using the addresses in the same order as when recording. Since this is done by specifying
The time series of the output data of the TBC 18 is the same as that at the time of recording.

In the embodiment described above, the number of revolutions of the rotary head 2 during reproduction is larger than that during recording, for example twice, but the number of traces during reproduction can be made larger than that during recording by other means. You can do it like this. One of them is to make the rotating speed of the rotary head the same during recording and reproducing, and increase the number of heads used during reproducing compared to recording. For example, two rotating heads are arranged at a distance of 180° from each other, and recording is performed using only one of them.
It is possible to perform reproduction using both of them. Another method is to use one rotary head that rotates at the same number of revolutions during recording and playback, and use this head to record data on, for example, every other track during recording, so that the playback locus is There are ways to avoid leaving books behind.

In addition, in the above-mentioned embodiment, the head width during playback is
Although Wh is assumed to be equal to the track width Wt of the recording track, the relationship (Wh>Wt) may also be established. For example, when (Wh = 1.5Wt), Fig. 6 A
Reproduction signals S ₁ to _{S 4} as shown in FIG.
Corresponding playback data DT ₁ ~ as shown in Figure B
DT ₄ D are obtained sequentially. Moreover, when (Wh=2Wh), the reproduced signals S ₁ to _{S 4} as shown in FIG.
are obtained sequentially.

As is clear from these figures 6 and 7, by setting (Wh > Wt), the S/
N can be made better. On the other hand, since crosstalk occurs because two or more recording tracks are scanned at the same time, it is necessary to take countermeasures against crosstalk.

As can be understood from the above explanation, according to the present invention, there is no need for tracking in which the head scans one-to-one with the recording track, so there is no need to perform high-precision tracking servo, and there is no need for mechanical tracking. Freed from precision. In other words, firstly, it is not necessary to specify the positional relationship between the recording track and the reproduction scanning trajectory, so a highly accurate phase servo is not required. do not have to match, so
The accuracy of the tape path may be low, and thirdly, the recording track or reproduction scanning trajectory may meander.
The accuracy of the tape path does not need to be low.Fourthly, when winding the magnetic tape around the tape guide drum, there is no need to apply lateral pressure to the magnetic tape to regulate the position of the tape edge on one side. It is possible to make the sliding contact state with the material stable. For these reasons, it is also possible to form the tape guide drum from molded plastic.
A rotary head type regenerator can be easily and inexpensively manufactured.

It goes without saying that the present invention can also be applied to the reproduction of digital information signals such as digital video signals and measurement data in addition to digital audio signals.

[Brief explanation of drawings]

1 and 2 are schematic diagrams showing the mechanical structure and recording pattern of an embodiment of the present invention, and FIG. 3 is a block diagram showing the structure of a recording system and a reproducing system of an embodiment of the invention. FIG. 4 is a schematic diagram showing the structure of recorded data, FIG. 5 is a schematic diagram and time chart used to explain the operation of one embodiment of the present invention, and FIGS. 6 and 7 are respectively diagrams of other embodiments of the present invention. This is a time chart used to explain examples. 1a and 1b are tape guide drums, 2 is a rotating head, 3 is a magnetic tape, 18 is TBC, Tn _-1 , Tn,
Tn ₊₁ is a recording track, and _N1 to _N5 are reproduction scanning trajectories.

Claims (1)

[Scope of Claims] 1. A block is constructed for each digital information signal of a predetermined length, a block address signal is added to each block, and n recording tracks on which a predetermined number of blocks are recorded are reproduced from the recording track pitch. A rotary head that scans at least n times to reduce the scanning pitch, and a memory in which the digital information signal reproduced by the rotary head is written in accordance with the reproduced block address signal, 1. A rotary head type reproducing device characterized in that digital information signals written in a memory are made continuous by reading them in a predetermined order. 2 A signal for detecting an error in the block address signal is added to the block, and when there is an error in the block signal reproduced during reproduction, writing of the reproduced digital information signal to the memory is prohibited. A rotary head type reproducing device according to claim 1, characterized in that: