JPS6320772A - Multi-channel type digital signal reproducing device - Google Patents

Abstract

PURPOSE:To avoid centralization of error data and to secure the satisfactory correction of error data by having different combinations of plural tracks between at the times of recording and reproduction. CONSTITUTION:The tracking control is carried out so that rotary heads 6A and 6B scan correctly on a magnetic tape by a servo circuit related to a capstan motor 20. The phase of a reproduction control signal is shifted by a delay circuit 23 and this shift value corresponds to the value that causes a track shift between the times of recording and reproduction. Therefore a set of two tracks which are reproduced at a time like (B1, A2)(B2, A3)... are shifted by a track against the recording mode. Both tracks B1 and A2 are scanned at a time and the error data are produced at an approximately same position as shown by X. If these error data are uncorrectable, the video data on different areas are recorded on the tracks B1 and A2. Thus the error data are satisfactorily corrected by correction circuits 13A and 13B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-channel digital signal reproducing device commonly used in digital VTRs that records/reproduces digital video signals using a rotary head.

[Summary of the invention]

The present invention provides a multi-channel digital signal reproducing device that reproduces a recording medium in which a time series of a digital information signal is distributed into data of a plurality of channels, and data of the plurality of channels are simultaneously recorded in sets of a plurality of tracks. , the set of tracks that are simultaneously reproduced is made different from the set of tracks that are recorded, preventing error data from occurring in close positions on the screen, and correcting the error data in a good manner.

[Conventional technology]

Since the data rate of recorded data is high in a digital VTR that records/reproduces digital video signals using a rotating head, multi-channel recording is performed in which recorded data is distributed and recorded on a plurality of parallel tracks. For example, the screen of one field of a digital video signal is vertically divided into three parts, and the data of each area is recorded as two parallel tracks.

FIG. 5 shows a recording pattern in a conventional digital VTR, where T is the running direction of the magnetic chip 17.

S is the scanning direction of the rotating head. The digital signal for one field is divided into two channels of recording data, and the recording data of each channel is supplied to two channels of rotary heads. The wooden tracks are formed simultaneously.A wrap of about 300° is wrapped around the corner of a rotating drum fitted with a two-channel rotating head, and the rotating drum is rotated three times during one field. Therefore, (AL, B1) (A2.B
2) One field of digital video signal is recorded as (2 channels x 3 = 6) continuous tracks of (A3.B3).

Between the 1-field screen and the recording pattern described above,
There is a correspondence relationship shown in FIG. In other words, the screen of one field is vertically divided into three parts, the video data of the upper area is recorded on tracks Al and B1, the video data of the middle area is recorded on tracks A2 and B2, and the video data of the lower area is recorded on tracks A2 and B2. Data is recorded on tracks A3 and B3.

During reproduction, the gutter simultaneously scans [(Ai, Bi) of the two tree tracks in the same relationship as during recording.

(Problems to be Solved by the Invention) In conventional multi-channel digital VTRs, tracking errors caused by poor running of the magnetic tape 70 during playback, poor contact between the tape and the rotating head, etc.
In FIG. 5, as indicated by x, tracks A2 and B
2, the positions of these error data will be close to each other in the screen of one field. Digital VTRs usually use error correction codes, and error data that cannot be corrected by the error correction code is corrected with correct data surrounding the error data. However, as mentioned above, since the error data is located close to each other, there is a risk that the error data may not be repaired satisfactorily in a conventional digital VTR.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a multi-channel digital signal reproducing apparatus that prevents error data from being concentrated in close proximity and is advantageous in terms of correction.

[Means for solving problems]

The present invention relates to a multi-channel digital signal reproducing device that reproduces a recording medium in which a time series of a digital information signal is distributed into data of a plurality of channels, and data of the plurality of channels are simultaneously recorded in sets of a plurality of tracks. This is a multi-channel digital signal reproducing apparatus in which a set of a plurality of tracks to be simultaneously reproduced is different from a set of a plurality of tracks to be recorded.

[Effect]

As an example, 2 records/plays back two tracks in parallel.
In the case of a channel-type digital VTR, a set of two tracks (
A1. Bl) (A2.B2) ..., one track is shifted, and (B1.A2) (B2.A3
) ... are simultaneously scanned by the rotating head during playback. Therefore, when error data occurs due to traversing errors, poor contact between the tape and the rotary head, etc., error data can be prevented from occurring in close positions on the screen, and the error data can be properly corrected. Ru.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the first M, a digital video signal is supplied to an input terminal designated 1. This digital video signal is supplied to the distribution circuit 2.

In the distribution circuit 2, one word (1 sample data, 8 bits, 8 bits) in a time series of a temporally continuous digital video signal is alternately distributed to a first channel and a second channel.

The series data of the first channel is supplied to the recording encoder 3A, and the series data of the second channel is supplied to the recording encoder 3B. The recording encoders 3A and 3B encode error correction codes such as product codes, rearrange data, synchronize signals, and encode the series data of each channel.
Addition of address signals and identification signals such as fields, digital modulation, and other processing are performed. The output data of the recording encoders 3A and 3B are converted into serial data by parallel-to-serial conversion circuits 4A and 4B.

This serial data is transferred to the rotary heads 6A and 6B via recording amplifiers 5A and 5B and rotary transformers (not shown).
supplied to

Two channels of recording data are recorded on the magnetic tape 7 as two parallel tracks by the rotary heads 6A and 6B. The magnetic tape 7 is rotated through the rotation nodes 6A and 6.
B is wound over an angular range of approximately 300° around the circumferential surface of the rotating drum to which B is attached, and is run at a predetermined speed by a capstan 8 and a pinch roller 9. The rotating heads 6A and 6B are rotated three times in one field period.

FIG. 2 shows a recording pattern formed on the magnetic tape 7. As shown in FIG. T indicates the running direction of the magnetic chip 17, and S indicates the scanning direction of the rotary heads 6A, 6B. Data for one field period is transferred to two tracks by the two-channel rotary head.
Tracks with each set of Tsuku (A1.Bi) (A2.B
2) Recorded in (A3.B3). The correspondence between these tracks and one field screen is as shown in FIG. In other words, the screen is vertically divided into three parts, the digital video signal in the upper area is recorded on tracks A1 and B1, the digital video signal in the middle area is recorded on tracks A2 and B2, and the digital video signal in the lower area is recorded on tracks A2 and B2. Signals are recorded on tracks A3 and B3.

At the time of reproduction, the rotary heads 6A and 6B7)<% solemn tape 7 are scanned, and two-channel reproduction signals are obtained. By the operation of a capstan servo circuit, which will be described later, the set of two tracks simultaneously scanned during reproduction is shifted by one track from that during recording. In the recording pattern shown in the second group, during recording, the rotary head 6A forms a track A1, and the rotary head 6B forms a track B1. During reproduction, the scanned track is shifted by one track, so that the rotary head 6A scans the track B1, and the rotary head 6B scans the track A2. Similarly, (B2.A3) (B3.A4)
... are sequentially scanned.

The reciprocating signal from the rotary head 6A is supplied to the serial-parallel conversion circuit 11A via the reproduction amplifier IOA, and the parallel data from the serial-parallel conversion circuit 11A is supplied to the reproduction decoder 12A.
supplied to Similarly, the reproduction signal from the rotary head 6B is supplied to the serial-parallel conversion circuit 11B via the reproduction amplifier IOB, and the parallel data from the serial-parallel conversion circuit 11B is supplied to the reproduction decoder 12B. Playback decoder 12
In A and 12B, processing is performed such as removing one time axis variation of demodulation of digital modulation, decoding an error correction code such as a product code, and rearranging the data arrangement to return it to the original order.

Output data from reproduction decoders 12A and 12B are supplied to modification circuits 13A and 13B, respectively. Modification circuit 1
In 3A and 13B, error data that could not be corrected using the error correction code is interpolated with neighboring correct data. For example, this error data is interpolated by the average value of two correct data located on the left and right sides of the error data. The first signal obtained from each of the modification circuits 13A and 13B
The series data of the second channel and the series data of the second channel are supplied to the combining circuit 14. In the synthesis circuit 14, one word is alternately selected from the series data of each channel, and a reproduced digital video signal of one channel is obtained at the output terminal 15.

A phase servo circuit and a speed servo circuit are provided for a capstan motor (eg, a DC motor), shown at 20. Servo control signals are recorded in the magnetic tee 17 in its longitudinal direction, although not shown. - As an example 2
Wooden truck (Ai.

A control signal is recorded near the lower edge of the magnetic chip 17 for each group Bi). This control signal is reproduced by a fixed magnetic node 21 and supplied to a phase comparison circuit 24 via a reproduction amplifier 22 and a delay circuit 23.

A servo reference signal from a terminal 25 is supplied to the phase comparison circuit 24 . This servo reference signal is a digital VT
This signal is synchronized with the R reference synchronization signal and has a frequency three times the field frequency. The phase comparison circuit 24 generates a DC voltage (phase error signal) proportional to the phase difference between the reproduced control signal and the servo reference signal. This phase error signal is supplied to adder circuit 26.

Further, a detection signal having a frequency proportional to the rotational speed of the capstan motor 20 is generated from the rotation detector 27. The detection signal from this rotation detector 27 is transmitted to the speed servo circuit 28.
supplied to The speed servo circuit 28 measures the period of the detection signal, and detects the difference (speed error) between the measured period and a reference value. The speed error signal and phase error signal from the speed servo circuit 28 are added by an adder circuit 26, and the output signal of the adder circuit 26 is supplied to the capstan motor 20 via a motor drive circuit (not shown).

A servo circuit provided in connection with the above-mentioned capstan motor 20 performs tracking control in which the rotary heads 6A, 6B correctly scan the tracks on the magnetic tape 7. The delay circuit 23 shifts the phase of the reproduction control signal. This shift ffi corresponds to the amount of track deviation of one track between the recording operation and the reproducing operation. Therefore, as mentioned above, the set of two tracks played at the same time is (B1.A2) (B2°A
3) (B3.AI) . . . is shifted by one track with respect to the recording time.

As an example, when two tracks (B1 and A2) are simultaneously scanned by the rotary heads 6A and 6B, due to the instability of the contact between the rotary heads 6A and 6B and the magnetic tape 7,
As shown by the cross in FIG. 2, track B1. Error data occurs at substantially the same position in A2. If these error data cannot be corrected, the correction circuit 13A
, 13B. As can be seen from FIG. 3, video data recorded on track B1 and track A
Since the video data recorded in 2 is data in a different area, the error data can be successfully corrected in the correction circuits 13A and 13B. In particular, since the series data of a digital video signal is distributed and recorded into series data consisting of even-numbered words and series data consisting of odd-numbered words, the even-numbered words or odd-numbered words of the series data in each area are Only one of the words becomes error data. Therefore, it is easy to interpolate the error word by the average value of the correct words located before and after the error word, respectively.

In this embodiment, data from two tracks that are played simultaneously are thick (separated) on the time axis, and
A large capacity memory is required to remove time axis fluctuations. However, the reproduction decoders 12A, 1
2B is provided with a field memory or a frame memory for rearranging the data arrangement, etc., and the time axis can be corrected without any trouble in this field memory or frame memory.

Unlike the embodiment described above, the present invention can be applied to a digital VTR that scans three or more tracks simultaneously. For example, when four tracks are simultaneously scanned, the set of tracks during reproduction is shifted by two tracks from the set of tracks during recording.

In addition to the capstan servo circuit, a rotating head is attached to a bimorph plate made of two piezoelectric elements and a control signal is supplied to the bimorph plate in order to shift the set of tracks between recording and playback. can be used.

When a bimorph board is used, the response speed of tracking control can be increased, and it is effective when applied to, for example, playback of insert-edited magnetic tape.

In FIG. 4, tracks A1. Bl, A2, B2
．． A3 indicates a recording pattern in which inserts i are collected on the magnetic tape 7 in which tracks 83', A1', and B1' indicated by broken lines are recorded. In conventional digital VTRs, (A
1. Since the set of tracks Bl)(A2°B2)(A3.83') are played back sequentially, due to the rapid change in track pinch, the data on track B3' is not played back correctly, and the data on track B3' is not played back correctly until the tracking servo is activated. Data at the beginning of the tracks (AI', Bl') reproduced during this period is also not reproduced correctly. As a result, there is a problem in that error data is generated intensively on the screen, making correction difficult.

In this invention, the recording pattern shown in FIG.
2) (B2.A3) (B3', AI') (Bl',
When the set of tracks A2') is reproduced, a large error occurs in the data of track B3' and the beginning of track Al'. In this case, the envelope of the playback output of track A1' is detected, and a control signal for the bimorph board is formed from the change in the envelope, thereby correcting the tracking deviation between the latter half of track Al' and track B1'. Can be done.

Therefore, at least the same percentage of data of the digital video signals recorded on the track AI' and the track B1' can be obtained, and the correction can be performed satisfactorily.

The present invention is a digital audio system that separates the time series of digital audio signals into series data consisting of odd-numbered words and series data consisting of even-numbered words, and records these series data on two parallel tracks. It can be applied to audio signal playback devices.

〔Effect of the invention〕

In this invention, since the series data of multiple channels played simultaneously from multiple tracks are data at distant positions on the time axis of the data time series, concentration of error data is prevented and error data can be corrected effectively. done to.

[Brief explanation of drawings]

The first view is a block diagram of an embodiment of the present invention, Figure 2 is a route diagram of a recording pattern used to explain an embodiment of this invention, and Figure 3 is a track diagram used to explain an embodiment of this invention. FIG. 4 is a route map showing the correspondence relationship between screens. FIG. 4 is a route map of an edited recording pattern used to explain an embodiment of the present invention. FIGS. 5 and 6 are recording patterns used to explain a conventional digital VTR. It is a route map showing the correspondence relationship between trucks and screens. Explanation of main symbols in the drawings 6A, 6B: Rotary head, 7: Magnetic tape, 13A
, 13B: Modification circuit, 15: Output terminal for reproduction digital video signal, 20: Capstan motor, 24
: Phase comparison circuit.

Claims (1)

[Claims] A multi-channel digital signal in which the time series of a digital information signal is distributed into data of a plurality of channels, and the data of the plurality of channels is reproduced from a recording medium on which the data of the plurality of channels are simultaneously recorded as a set of tracks. A multi-channel digital signal reproducing device, characterized in that a set of a plurality of tracks to be played back simultaneously is different from a set of a plurality of tracks to be recorded.