JP2664987B2 - Digital video signal recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video signal recording apparatus for performing normal recording and long-time recording of a digital video signal.

2. Description of the Related Art As a recording mode in a conventional analog VTR, for example, a VHS system VTR, there are a normal recording mode and a long-time recording mode as shown in FIG. In the normal recording mode shown in FIG. 5 (a), a diagonal 1 having a track pitch of 58 μm is used.
An analog video signal of one field is recorded on a track. In the longitudinal direction control track CT, a signal for controlling the tape feeding speed, and about 30 signals for the NTSC video signal are recorded. In the case of the long recording mode shown in FIG. 5B, the tape feed speed is reduced to 1/3 and the track pitch is set to 19
By setting it to μm, three times the recording time is obtained.

FIG. 6 shows a rotary head type signal recording apparatus for performing the above recording, wherein 25 is a rotary drum, 26 is a magnetic tape, and 27 and 28.
Is a magnetic head attached to the rotating drum 25. The rotating drum 25 is rotating at about 1800 RPM, and sequentially records one field (about 60 Hz) of analog video signals on one track on a magnetic tape 26 wound around 180 °. Here, 1, 2, 1, 2,... On the track pattern indicates one of the magnetic heads 27, 28. The magnetic heads 27 and 28 are shown in FIG.
This is a so-called combination head in which two heads having different track widths are mounted close to each other to realize the track pattern of (b).

In conventional VTRs, recording is performed for a long time by changing the track pitch.In the long-time mode, the quality of the video signal deteriorates.However, it is used when high quality is not required or when long-time recording is required. I have.

[Problems to be solved by the invention]

However, when recording a digital video signal, the recording is performed so that the areal recording density, that is, the track pitch and the linear recording density are optimized. Therefore, there was a problem that recording and reproduction of digital signals became impossible.

It is also conceivable to perform recording with the drum rotation speed reduced to 1/3. However, since the relative speed between the head and the tape changes, there has been a problem that it is difficult to perform optimal recording due to a change in electromagnetic conversion characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and performs recording in the normal recording mode and the long-time recording mode without changing the track width and the number of rotations of the drum, that is, without changing the electromagnetic conversion characteristics. It is an object of the present invention to obtain a digital video signal recording device capable of performing the above.

[Means for solving the problem]

The digital video signal recording device according to the present invention has N
In the long double recording mode, the tape feed speed is set to 1 / N of the normal mode, and the digital video signal of one field is set to 1 / N.
What was recorded on the M tracks in the normal recording mode at the rate of the normal recording mode was changed to the L / R track unit using the L-channel rotating head for the M / N tracks without changing the drum rotation speed. Is used to record intermittently.

[Action]

In the present invention, the digital video signal of one field compressed to 1 / N is intermittently recorded on M / N tracks, so that the surface recording density is kept constant and the track width and the number of rotations of the drum are not changed. In addition, recording can be performed while keeping the electromagnetic conversion characteristics constant. Since recording is performed in units of L tracks, each track is a straight track.

〔Example〕

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

FIG. 1 is a diagram showing a recording track pattern in a digital video signal recording device according to one embodiment of the present invention. FIG. 1A shows a track pattern in the normal recording mode, and...,... Represent field numbers. In the long-time recording mode shown in FIG. 1B, the feed rate is set to 1 / N (N = 3 in this case), the data rate is set to 1 / N, and intermittent recording is performed in units of N fields. In FIG. 1B, the track length of one field is as shown in FIG.
Although it is 1 / N, the track pitch is the same.

A digital video signal recording apparatus for generating such a track pattern will be described with reference to the block diagram of FIG. In FIG. 2, 1 is an input terminal for an analog video signal, 2 is a low-pass filter for band limitation, 3 is an analog / digital (A / D) conversion circuit, 4 is a data compression circuit I for a normal recording mode, and 30 is a long circuit. Data compression circuits II and 5 for the time recording mode are selectors for selecting the outputs of the data compression circuit I4 and the data compression circuit II30, and 6 is a data compression circuit for correcting and interpolating a code error caused by dropout or the like occurring on the magnetic tape. An encoder for performing shuffling and error correction encoding, 7 is a modulator for recording and reproducing digital data on a magnetic tape, 8 is a recording amplifier, 9 is a rotating drum, and 10 and 11 are mounted on a rotating drum. Rotating head, 12 is a magnetic tape, 13 is a fixed head for recording control signals for capstan servo, 14 is a capstan motor for running the tape, 15 is a capstancer A reproducing circuit, 16 a demodulator for converting a reproduced signal from a magnetic tape into digital data, 18 a decoder for error correction and data rearrangement, 19 and 31 compressed data I, I
Data decompression circuits I, II and 20 for returning I to the original video signal are selectors for selecting the outputs of data decompression circuits I19 and II31, 21 is a digital / analog (D / A) conversion circuit, and 22 is a low-pass filter 23, a video signal output terminal; and 24, a control circuit.

For example, an NTSC composite video signal is input from an input terminal 1, and a video signal controlled to a band of 4.2 MHz by a low-pass filter 2 is converted into a color subcarrier frequency F _SC (≒ 3.58 MHz) by an A / D conversion circuit 3. Sampled at twice the frequency,
It is quantized to 8 bits. The rate of the digital video signal is about 4 × F _SC × 8 ≒ 125 MBPS. Effective data rate excluding vertical and horizontal blanking data is about 90 MBPS
The data compression circuit 14 compresses the data to 1/3 30 MBPS, the data compression circuit II30 compresses it to 1/9 10 MBPS, and the selector 5 selects either the output of the compressed data I or the output of the compressed data II.
The encoder 6 shuffles the data and adds an error correction code. The compressed data I is about 40 MBPS, and the compressed data II is 13 MBPS.
It will be about PS rate. The signals arranged in the order to be recorded on the magnetic tape are subjected to digital modulation such as 8/10 modulation by the modulator 7 and sent to the rotating drum 9 through the recording amplifier 8. Digital video signals are recorded on the magnetic tape 12 from the rotary heads 10 and 11 via a rotary transformer (not shown) in the rotary drum 9.

In the normal recording mode, that is, when the compressed data I
To record a 40 MBPS digital video signal on a 1 / 2-inch wide magnetic tape, for example, rotate the rotating drum 30 times /
Recording can be performed by setting the magnetic heads 10 and 11 to 2-channel heads in seconds (RPS). Therefore, the track of the field 1 in FIG.
It is a book. At this time, the video signal of one field is M = 2
A signal of 30 Hz is recorded on the track of the book, and the fixed track 13 is recorded on the control track CT.

In the long recording mode, that is, when the compressed data II
To record a 13 MBPS signal, the capstan servo circuit 15 controls the capstan motor 14 to reduce the tape feed speed to 1/3 while keeping the rotation speed at 30 RPS. 1 and the intermittent recording is performed only at the "L" level, so that the track of the field shown in FIG. can do.

This recording timing will be described in more detail with reference to the timing chart of FIG. FIG. 3 (a) shows a normal recording mode in which the video fields (a),... Of (f) are A / D-converted corresponding to the 30 Hz signal of (a), and the data compression I and the encoding are performed during the period (g). Is performed, and recording is performed on the magnetic tape during the period of (h). In the long-time recording mode shown in FIG. 3B, the A / D conversion period (f), the data compression II and the encoding period (v) are the same, but the recording timing on the magnetic tape is ( Record all three fields together as in d). In other words, recording is performed for each track by performing recording for only half a rotation during one half rotation of the drum rotation.

FIG. 4 shows a signal format for performing such track formation. FIG.
One segment represents a preamble, a plurality of data blocks, and a postamble. 1
The data block is composed of a header, data and an error correction code as shown in FIG. 4 (b), and the digital video signal corresponds to this data portion. Further, the header includes a synchronization signal, an address, an identification code (ID), as shown in FIG.
It consists of parity, and the identification signal of the normal recording mode / long time recording mode is put in the ID part.

If the segment in FIG. 4A is set to one for the track pattern in FIG. 1B at the time of compression, one diagonal track can be constituted by three segments, and the track in the normal recording mode is also included. It can be easily configured.

By the way, at the time of reproduction, the rotating drum 9 is rotated at 30 RPS,
By controlling the capstan motor 14 with the capstan servo circuit 15 so that the signal reproduced by the fixed head 13 from the control track CT becomes 30 Hz, each of which is recorded in both the normal recording mode and the long recording mode It is possible to play the track.

The signals reproduced from the rotating magnetic heads 10 and 11 are amplified by a reproduction amplifier 16, then subjected to equalization, clock reproduction and signal detection by a demodulator 17, returned to digital signals, and then inverted by a modulator 7. Is converted into the original digital video signal according to the conversion rule. The decoder 18 performs time axis correction, error correction, inverse shuffling, and interpolation processing. The compressed video data I is expanded by the data expansion circuit I19 for compressed data I, and is expanded by the data expansion circuit II31 for compressed data II. Return to signal. In the selector 20, in the normal recording mode, the data decompression circuit I1
9 in the long time mode, the data expansion circuit II31
, Is converted to an analog video signal by a D / A conversion circuit 21, and is output from an output terminal 23 by a low-pass filter 22 excluding signals outside the band.

Since the drum rotation speed and the track width in the normal recording mode and the long-time recording mode are the same, the quality of the reproduced signal is the same, and it is not necessary to switch the circuits for demodulator 17 equalization, clock reproduction, signal detection, etc. Not at all.

In the above embodiment, the case where the drum rotation speed is 30 RPS and a two-channel head is used has been described. However, the present invention can be applied to any drum rotation speed and head number.

The normal recording mode may be uncompressed, and the long-time recording mode may be compressed.

〔The invention's effect〕

As described above, according to the present invention, in the N-times long-time recording mode using the L-channel head, the tape feed speed is set to 1 / N, and the drum rotation speed and the track width are not changed.
Since the digital video signal of the field is intermittently recorded on the M / N tracks in units of L tracks, each track becomes a straight line, and the quality of the reproduced signal from the tape does not change. There is an effect that a high digital video signal recording device can be obtained.

[Brief description of the drawings]

FIG. 1 is a track pattern diagram of a digital video signal recording apparatus according to one embodiment of the present invention in a normal recording mode and a long time recording mode, and FIG. 2 is a digital video signal recording and reproducing apparatus of one embodiment of the present invention. FIG. 3 is a recording timing diagram in one embodiment of the present invention, FIG. 4 is a signal format diagram used in the present invention, FIG. 5 is a track pattern diagram by a conventional video signal recording device, FIG.
FIG. 1 is a schematic diagram for explaining the arrangement of a conventional magnetic head. 1 is an input terminal, 4 is a digital compression circuit I, 30 is a data compression circuit II, 9 is a rotating drum, 10 and 11 are rotating magnetic heads, 12 is a magnetic tape, 13 is a fixed head, 14 is a capstan motor, and 15 is a capstan motor. A capstan servo circuit 24 is a control circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A video signal of one field is represented by M (M: integer).
L (L: L:
A digital video signal recording apparatus for recording by using a rotating head having (even number) channels, and in a case of performing N (N: real number) times long time recording, a tape feed speed is set to 1 / N and a signal of one field is used. Is recorded intermittently on substantially M / N tracks in units of L tracks.