JPH07244934A - Device for recording/reproducing digital signal - Google Patents

Abstract

PURPOSE:To verify whether or not a digital signal is recorded correctly without a special head. CONSTITUTION:The recording data from a buffer memory 2 are supplied to the head Ha through an ID addition circuit 3, a parity generation circuit 4 and a recording/reproducing switch 7, etc., to be recorded on a tape by the head Ha. The rate of the recording data is made a speed lower than a standard one, and recording operation is performed intermittently. In the period when no recording operation is performed, a digital signal recorded immediately before is reproduced by the head Ha. In an error correction circuit 11, the regenerative data are error corrected, and whether or not the recording is performed correctly is judged from the result. When the recording is failed, the same data are recorded by a controller 13. Together with that, an ID indicating that these are the re-recorded data is added. At an original reproducing time, whether or not these are the re-recorded data is obtained by the ID.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal recording / reproducing apparatus for recording / reproducing digital signals having different data rates.

[0002]

2. Description of the Related Art In a digital signal transmission system such as a digital CATV, it is conceivable to use a rotary head type digital VCR (digital cassette recorder) as a digital signal storage device of a terminal.
An example of a conventional digital VCR will be described. Figure 5
5A shows the arrangement of the magnetic heads, and FIG. 5A shows the magnetic heads Ha and Hb attached to the rotating drum D at 180 °. FIG. 5B is an example in which the magnetic heads Ha and Hb are attached to the rotating drum D at extremely close positions. The magnetic head as shown in FIG. 5B has an integral structure and is called a double azimuth head.

On the peripheral surface of the drum D, although not shown, 18
The magnetic tape is wound with a winding angle slightly larger than 0 °, and the magnetic tape is fed at a constant speed. Digital video signals are sequentially recorded on the magnetic tape as diagonal tracks by the magnetic heads Ha and Hb. In order to suppress crosstalk between adjacent tracks, the gap extension direction of the magnetic head Ha and that of Hb are different from each other by a predetermined angle. As a result, azimuth loss generated during reproduction can reduce crosstalk between adjacent tracks.

Digital video signals, audio signals accompanying the video signals, and subcodes for control and the like are recorded on a magnetic tape in a format as shown in FIG. 6, for example. An ITI area, an audio area, a video area, and a subcode area are sequentially formed on one track according to the scanning order of the head, and a section where no data is recorded is provided between these areas. Briefly describing each area, the ITI area includes a preamble, a track information area, a postamble, and the like.

In the audio area, error-correction-coded PCM audio signals are recorded. The error correction coded digital video signal is recorded in the video area. Further, control codes such as information for high speed search are conducted in the sub code area. The subcode is also error correction coded.

The standard data rate of the recording data generated in the recording processing circuit is set to 25 Mbps, for example. The drum D is rotated at a predetermined rotation speed (for example, 9000 rpm) and the magnetic tape is rotated at a standard speed (for example, 1 rpm).
When sent at 8.8 mm / sec), one frame of video signal is recorded as, for example, 10 tracks.

When such a digital VCR is used as a data storage device in a terminal of a digital CATV system, it is possible to record received digital data in a track, for example, in a video area without decoding it into image or audio data. is there. One problem in that case is that the data rate of the received digital data is variable. That is, the rate of the recording data formed from the received digital data does not always match the standard data rate.

The applicant of the present application has proposed an intermittent recording method in order to solve such a problem. In this, the drum rotation speed is set to a standard value, the tape feeding speed is set to a low speed in accordance with the rate ratio R, and the recording operation is performed intermittently. The rate ratio R is the rate of the recording digital signal x (<25
Mbps) and the standard rate is 25 Mbps, it is represented by (R = x / 25). By this intermittent recording, the track format and data structure can be made the same as those for the standard rate recording data.

If, for example, (R = 15), the tape speed is 1/15, so the trace position of the head on the tape changes as shown in FIG. FIG. 7 shows a part of the adjacent tracks Ta and Tb. The track Ta has the head Ha and the azimuth coincide with each other, and the track Tb has the head H.
b and azimuth match. As an example, the track pitch Tp is 10 μm and the head width is 13 ± 1 μm. First, recording is performed on the track Ta by the head Ha. Next, the position where the head Hb has advanced with respect to the track Ta (Tp / 15 = 0.667 μm) is traced. Further, next, the head Ha becomes (2Tp / 1
5) Trace the advanced position. And the track Ta
Is recorded 15 times after the head is recorded, the head Hb
When the track traces the track Tb, the following recording is performed.

[0010]

SUMMARY OF THE INVENTION The present invention is intended to verify whether or not correct recording was performed immediately after the recording operation during the intermittent recording as described above. Especially, this verification is different from general data (non-continuous data such as computer programs) that cannot be corrected spatially or temporally, unlike the continuous data such as video data and audio data. is necessary.
Conventionally, for such verification, a dedicated head separate from the recording head is required, which causes a problem of complicated head configuration and increased cost.

Therefore, it is an object of the present invention to verify whether or not the immediately preceding recording was correctly performed at the time of intermittent recording for recording low-rate data, and to record a digital signal which does not require a special head. It is to provide a reproducing apparatus.

[0012]

SUMMARY OF THE INVENTION The present invention has a recording / reproducing mechanism including at least a pair of rotary heads and tape feeding mechanisms having different azimuths, and a standard data rate and a data rate of a digital signal to be recorded. In a digital signal recording / reproducing apparatus in which a tape is fed at a speed corresponding to the ratio, and an input digital signal is intermittently recorded corresponding to the ratio, a recording pause period existing during intermittent recording. In, the recording / reproducing of the digital signal is performed such that the rotating signal recorded immediately before is reproduced at least once by the rotating head whose azimuth is the same, and the recorded digital signal is reproduced at least once. It is a device.

[0013]

Since the recording operation is performed intermittently, there is a recording pause period between the recording operations. In this recording pause period, the data recorded immediately before can be reproduced by the rotary head of the same azimuth as the rotary head used for recording immediately before. The reproduction data can be used to verify the previous recording.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. In this example, for example, a pair of heads Ha and Hb are arranged at an opposing interval of 180 ° with respect to the drum D as described above.
Is used, and a tape head mechanism in which a magnetic tape is wound around the drum D with a winding angle of slightly larger than 180 ° is used. FIG. 1 shows a configuration related to one head, for example, Ha. Although not shown, the other heads Hb are also provided with the same configuration as in FIG.

In FIG. 1, reference numeral 1 is an input terminal to which data to be recorded (general digital data, video data, audio data, etc.) is supplied. The input digital signal is written in the buffer memory 2. An input digital signal is intermittently read from the buffer memory 2 according to the rate ratio R of the recording data to the standard data rate. For example, when the standard data rate is 25 Mbps and the recording data is 5 Mbps, the rate ratio becomes R = 1/5, and the buffer memory 2 outputs approximately 1/5.
A time-axis-compressed digital signal is output to. The rate ratio R is designated by the ID from the controller 13.

The output signal of the buffer memory 2 is supplied to the ID adding circuit 3. The ID adding circuit 3 is supplied with an ID for instructing the rate ratio R, an ID for instructing whether or not it is re-recorded data, and the like. The digital signal to which the re-recording ID is added by the ID addition circuit 3 is supplied to the parity generation circuit 4. The ID is recorded in an auxiliary data area, a subcode area, etc. provided in the video area or the audio area. The parity generation circuit 4 generates the parity of the error correction code. A product code or the like can be used as the error correction code. In addition, error correction coding having a stronger capability may be adopted for general digital data as compared with error correction coding for continuous data such as video data.

The recording data from the parity generation circuit 4 is supplied to the channel modulation encoder 5 and channel modulated. The output signal of the channel modulation circuit 5 is supplied to the head Ha via the recording amplifier 6 and the recording side terminal 8r of the recording / reproducing changeover switch 7. By the head Ha,
It is recorded as an oblique track on the magnetic tape. Regarding the data rate, attention is paid to the data rate of recording data between the parity generation circuit 4 and the channel modulation circuit 5. In the case of the standard data rate, the rate of this noted data is 25 Mbps, and in the case of the rate ratio R = 5, this is 5 Mbps.

A reproduction signal from the head Ha is supplied to the channel modulation decoder 10 via the reproduction side terminal 8p of the recording / reproduction changeover switch 7 and the reproduction amplifier 9. The demodulated output of the channel modulation decoder 10 is supplied to the error correction circuit 11. The error correction circuit 11 corrects an error generated in the recording / reproducing process. The output signal of the error correction circuit 11 is written in the buffer memory 12.
Also, the verification result PB of the reproduced signal from the error correction circuit 11
-OK is generated, and this PB-OK is supplied to the controller 13. As will be described later, the digital signal recorded immediately before is reproduced, it is verified whether the recording is correct, and the result is indicated by the PB-OK.

The buffer memory 12 is provided for rate conversion of the reproduced digital signal, and performs time-axis expansion opposite to that at the time of recording. The rate of extension depends on the rate ratio R. The reproduction signal of the original data rate is read from the buffer memory 12, and this is taken out to the output terminal 14. Further, a timing generation circuit 15 and a timing controller 16 are provided, and an RF switching pulse SWP is supplied to these circuits from an input terminal 17.

The RF switching SWP is a pulse signal synchronized with the rotation of the rotary head. When the rotation frequency of the drum to which the head is attached is F, a cycle t of 1 / F
Is included in the RF switching SWP. The head Ha traces the magnetic tape while the pulse SWP is at the high level, and the head Hb traces the magnetic tape when the pulse SWP is at the low level. The timing generation circuit 15 synchronizes with the traces of this head to obtain the buffer memories 2, 12
Control the write and read operations of. Further, the timing controller 16 controls the recording / reproducing changeover switch 7 and the recording / reproducing changeover switch (not shown) for the head Hb in synchronization with the trace of the head.

The intermittent recording operation will be described with reference to FIG. The RF switching pulse SWP has a cycle t of 1/150 (second) when the rotation speed of the drum D is 9000 rpm.
Have. The head Ha traces the magnetic tape during the high level period of the pulse SWP, and the head Hb traces the magnetic tape during the low level period. For example, in the case where the rate ratio is 1/15, during a period traced by the head Ha, a pulse RecEN (record enable) for performing a recording operation becomes active (high level), and then Rec after a period of 7.5 t.
EN becomes active. One track is recorded while RecEN is active. Rate ratio R
When the denominator of is an odd number, as can be seen from the above example, the head Ha and the head Hb can alternately perform the recording operation, and the azimuths of the adjacent tracks can be made different.

Then, during the period in which the PB (reproduction pulse) shown in FIG. 2 is at a high level, a reproduction signal is taken out from the head that has just recorded. Such a recording operation and a reproducing operation can be realized by controlling the recording amplifier 6 with the pulse signal RecEN and controlling the recording / reproducing changeover switch 7 and the reproducing amplifier 9 with PB. In FIG. 2, the recording current flowing through the head and the reproduction signal are partially enlarged.

When the track pitch Tp is 10 μm as in the example of FIG. 7 described above, for example, the head Ha records the record data, and then the head Ha records 0.667 μm.
Trace the track recorded just before the point where m has advanced. Therefore, compared with the case of just-on-track where there is no track deviation, 0.667 μm × 2 = 1.333 μ
A shift of m occurs. C for just-on-track
When / N is 0 dB, the C / N of the reproduction signal obtained by the next trace of the recording operation is -1.24 dB, which is not much deteriorated as compared with the case of just on track. This reproduction signal is used to verify whether or not the recording was done correctly.

Verification of the recording operation will be described with reference to FIG. The recording operation is, for example, 7.5 depending on the rate ratio.
RecEN goes high every t and data is recorded during this period. The data recorded by the head Ha is referred to as data 1, and the data subsequently recorded by the head Hb is referred to as data 2. The data 1 is then reproduced by the head Ha and supplied to the error correction circuit 11 via the reproduction amplifier 9 and the channel modulation decoder 10.

In the error correction circuit 11, the reproduced data 1 is error-corrected, and the verification result PB-OK is generated depending on whether or not an error that cannot be error-corrected remains. A high-level verification result PB-OK means that the recording was done correctly, and a low-level verification result means that the recording failed. In this case, the verification may be performed by comparing the recorded data and the reproduced data. Even if the error can be corrected, if the amount of error is equal to or larger than the predetermined amount, it may be treated as a recording failure. Then, the verification result PB-OK is supplied to the controller 13.

FIG. 3 shows the case where PB-OK is at a high level for data 1 and the case where it is not. When PB-OK is at a high level, new recording data is recorded as data 2 after data 1. On the other hand, when the PB-OK after recording the data 1 is at a low level, it means that the recording of the data 1 has failed, and therefore the same data as the data 1 is recorded again as the data 2. For this re-recording, controller 1
3 controls the buffer memory 2 to output the same data as the previously recorded data. At the same time, the controller 13 generates an ID indicating that the data is re-recorded data, and the ID adding circuit 3 adds the ID to the re-recorded data 2. I for rerecording data
By D, the data of the track before the re-recorded data is treated as invalid data in the original reproducing operation. In this case, correct data among the data of the previous tracks may be effectively used.

Note that continuous data such as video and audio data may be distinguished from non-continuous general data such as computer program data, and the above verification may be performed only on general data. . More specifically, an ID indicating the type of recording data is supplied to the timing controller 16, and only when the recording data is general digital data, the terminal 8p on the reproducing side only for a predetermined period.
The recording / reproducing changeover switch 7 is controlled so as to select. The ID indicating the type of data is generated by the user's own input, the judgment of the system controller, the transmission from the broadcasting station in the case of digital CATV, or the like.

Further, as shown in FIG. 4, when re-recording, the order of data may be different between adjacent tracks. That is, the first data 1 to be recorded is divided into two equal parts, one half portion 1a thereof is recorded in the first half of the track, and the other half portion 1b is recorded in the latter half of the track. Then, when re-recording the same data, one half portion 2b (which is the same data as 1b) of the re-recorded data is recorded in the first half of the track, and the other half portion 2a (this is the same data as 1a) is recorded in the second half of the track. To record.

By thus changing the order of the recording data in the longitudinal direction of the track, it is possible to reduce the possibility that both data 1 and data 2 become error data due to the scratches in the longitudinal direction of the tape. That is, due to the scratches on the lower side of the tape, the data 1a and 2b
Even if becomes error data, data 1b and data 2
Correct data can be obtained by combining a. Not only the division of FIG. 4, but a larger number of divisions is possible.

In the above embodiment, when recording fails,
The same data is recorded again. However, the present invention is not limited to this, and a warning indicating that recording has failed may be generated. Further, the reproduction operation for verifying the recording just before is not limited to the trace period of the head immediately after recording,
If the necessary C / N can be secured, it can be performed in the trace period after the next recording period.

[0031]

As described above, the present invention is the same as the recording head because the recording is verified by using the recording pause period when the intermittent recording is performed in order to record the recording data having the data rate lower than the standard one. Can use the head of
There is an advantage that the recording head and a separate head are not required and the configuration is simple.

[Brief description of drawings]

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

FIG. 2 is a timing chart for explaining the operation of the present invention.

FIG. 3 is a timing chart for explaining a recording verification operation.

FIG. 4 is a schematic diagram for explaining a data re-recording operation.

FIG. 5 is a schematic diagram showing one example and another example of a head arrangement of a digital VCR to which the present invention can be applied.

FIG. 6 is a schematic diagram showing a recording pattern of a digital VCR.

FIG. 7 is a schematic diagram for explaining an intermittent recording operation.

[Explanation of symbols]

 Ha, Hb Rotating head 4, 6 Memory storing prediction coefficient 2, 12 Buffer memory 3 ID addition circuit 11 Error correction circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 20/12 103 9295-5D 27/28 A 8224-5D

Claims (5)

[Claims] 1. A recording / reproducing mechanism having at least a pair of rotary heads and tape feeding mechanisms having different azimuths, and having a speed corresponding to a ratio of a standard data rate to a data rate of a digital signal to be recorded, In a digital signal recording / reproducing apparatus in which the tape is fed and the input digital signal is intermittently recorded in correspondence with the ratio, recording is performed immediately before in a recording pause period existing between the intermittent recording. A digital signal recording / reproducing apparatus adapted to reproduce the digital signal recorded immediately before at least once by the rotary head having the same azimuth as that of the rotary head for performing the recording, and verify the recording from the reproduced signal. 2. The digital signal recording / reproducing apparatus according to claim 1, wherein when the input digital signal is general digital data,
A digital signal recording / reproducing device for selectively verifying. 3. The digital signal recording / reproducing apparatus according to claim 1, wherein the same data is recorded again when a recording failure is detected as a result of the recording verification. An apparatus for recording / reproducing a digital signal, wherein an identification signal for indicating that the signal is recorded is recorded together with the re-recorded data. 4. The digital signal recording / reproducing apparatus according to claim 3, wherein the identification signal indicating the re-recorded data treats the data with the minimum error as valid reproduced data. . 5. The digital signal recording / reproducing apparatus according to claim 3, wherein the same data is re-recorded on the tape in a data order different from the data order at the time of previous recording. apparatus.