JPS62171287A - Digital picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent mis-detection of a synchronizing code by recording a television signal subject to digital coding so as to arrange a synchronizing code block in adjacent tracks with an equal azimuth angle so as to forecast the detection time of the next synchronizing code. CONSTITUTION:An error correction (or detection) code P is added to a picture data D obtained from a television signal in a digital VTR. Further, the signals D, P are collected, an address A of a synchronizing code S is added and the result is used as one synchronizing block. The synchronizing code S has a pattern detected by a reproducing code and the location of the address A in the code, the data D and the section of the correction code P are confirmed by using the pattern. In this invention, the synchronizing blocks 2 are arranged between adjacent tracks on a tape 1. When the synchronizing code blocks are arranged between the adjacent tracks, the tape speed differs at the recording and reproduction and even when the head reproduces a signal while bridging over plural tracks at the reproduction, the reproduced synchronizing codes form a prescribed interval. AS a result, the detection of the synchronizing code is operated effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for converting an image signal into a digital code and recording it on a tape, and particularly relates to a recording format on a tape suitable for variable speed playback.

[Conventional technology]

When recording television signals in high-density analog fashion using the FM system, record without guard panning.

A method is also known in which the azimuth angle of the head is made different between adjacent tracks. A typical example of this is VHS
The method is called the β method.

For example, it is detailed in the October 1978 issue of the Journal of the Television Society.

Because the azimuth effect is effective for high frequency components.

As a result, crosstalk from adjacent tracks is almost suppressed, but since both the VH8 and β types record color signals in the low frequency component area, crosstalk of color signals becomes a problem. To solve this problem, recording signals are arranged in units of scanning lines between adjacent tracks, and in the β method, for example, recording is performed so that the phase of the color signal carrier wave is inverted for each scanning line. During reproduction, when the color signal is reproduced, the phase of the color signal carrier wave is inverted for each scanning line, and this is summed with a signal delayed by -scanning line, thereby suppressing the crosstalk component of the color signal from the adjacent track. What makes this possible is that the signals between adjacent tracks are lined up at the scanning line level, and the signals have a high correlation between the lined up scanning lines.

On the other hand, the television signal is converted into digital code and recorded. A so-called digital VTR is known. This provides the characteristic that the image quality does not deteriorate during the recording and reproducing process. In a digital VTR, in order to reduce the influence of code errors, the digital code obtained from the television signal is not required, and the order of pixels on a scanning line is not recorded. This is called shuffling. As a result, the concept of a scanning line does not exist in the recorded code series. Furthermore, in the case of digital recording, when a signal containing crosstalk from an adjacent track is decoded, it is not the sum of the original television signal and the crosstalk, but is converted into a completely different signal. As described above, since the situations are different between digital recording and analog recording, there has been no previous example of the relationship between recording codes between adjacent tracks in a digital VTR.

Note that crosstalk in digital VTRs occurs in the above situation, so either a guard band can be installed to prevent crosstalk from occurring, or in the case of guard panless recording, crosstalk can be suppressed using only the azimuth effect. Therefore, it is necessary to consider how to devise a code modulation method. Therefore, the relationship between adjacent tracks in a digital VTR needs to be considered not from the perspective of suppressing crosstalk, but from the perspective of smoothly performing playback at speeds other than the normal speed (still, slow, high-speed playback, etc.) described below.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a track pattern that allows accurate detection or prediction of synchronization codes when a digital VTR uses a tape speed different from that during recording and plays back while intersecting with a plurality of recorded tracks. be.

[Means for Solving the Problem] In a digital VTR, an error correction (or detection) code P is added to image data D obtained from a television program. Also, some D and P are collected, a synchronization code S address A is added to them, and this is made into one synchronization block.

In some cases, several synchronization blocks are collected and an error correction code is added to form a code block. Record these codes.

The address A indicates which track the image data D is recorded on, which code block it belongs to, which pixel on the screen it corresponds to, etc.

Furthermore, the synchronization code S has a pattern that can be detected from the reproduced code, and this is used to determine the position of the address A in the code, the data D, the delimiter of the correction code P, etc.

In the present invention, synchronization blocks 2 are arranged between adjacent tracks on a tape 1 as shown in FIG.

[Effect]

If m heads are arranged at equal intervals on a rotating drum (for example, at 90 degree intervals if m = 4) and the drum rotates n times per second, then the tape speed during recording is V per second.
When t cm is assumed, the inter-track distance Qam in the tape running direction is m.

On the other hand, if the code length of the synchronization block is B bits, the recording bit rate is Hit per second, and the relative speed of the head and tape is Vu-cm per second, then the length of the synchronization block on the tape, Lcm, is HBL = □ ・...(2).

Assuming that the angle between the recording track and the tape running direction is O, the condition for aligning synchronous blocks between adjacent tracks is Qcosθ=LX integer −・−・−(3′
). Although FIG. 1 shows an example in which the integer is 2, any integer value may be used.

Here, V H and θ are the rotational speed πdn of the head obtained from the diameter d of the drum for one rotation as shown in Fig. 2, and V
It is obtained from the vector sum of t. Here, φ is the angle between the rotating surface of the head and the tape scanning direction.

If the tape is played back at the same speed as the recording speed, the tape will follow the recorded track. If the tape speed during playback is greater than the tape speed during recording, high-speed playback occurs; if it is smaller, playback occurs at low speed; if the tape stops, playback is static; if the tape moves in the opposite direction to that during recording, playback occurs in reverse. The trajectories of the head during reproduction in these cases are shown in FIGS. 3 to 7. In either case, when the signals of a plurality of tracks are sequentially reproduced, the envelope of the reproduced code and the position of the synchronization code included therein are shown in FIGS. 4(a) and 4(b).

If formula (3) is satisfied, even if the synchronization code is played while crossing tracks, the intervals will be constant, and when the same track is played back (that is, when the tape speed is the same during recording and playback) The operation is the same as .

It should be noted that if the formula (3) is not satisfied, as shown in FIG. 4(C), the spacing will be equal within the same track, but the spacing will be discontinuous between tracks.

In addition, the synchronization code indicated by a dotted line in FIG. 4(b) is
Corresponds to areas where the envelope of the reproduced code is small and the signal-to-noise is poor, and as a result of code errors, the possibility that the synchronization code is not detected when it should be detected, or is detected in the image data when it should not be detected. Indicates that there is.

However, by utilizing the fact that the synchronization codes that should originally be detected are at equal intervals even if they cross tracks according to the configuration of the present invention, it is possible to prevent the synchronization codes from not being detected or from being detected too much.

In other words, the synchronization code can be detected by focusing only on the portion of the reproduced code where the synchronization code is likely to be present.

This prevents the image code from being mistakenly detected as a synchronization code. On the other hand, if no synchronization code is detected in the above part, the synchronization code can be detected by artificially inserting the synchronization code after a predetermined time from the previously detected synchronization code. This prevents erroneous detection.

[Embodiments of the invention]

FIG. 5 shows the basic configuration of a digital VTR.

The analog television signal applied to the terminal 8 is converted into a digital code by the A/D converter 9. Since this code is high-speed data of, for example, 100 Mb/s, it is difficult to record and reproduce it on a tape with a single magnetic head. Reference numeral 10 denotes a channel distribution circuit, which divides image data into four data streams each having a speed of 1/4 in the illustrated example. 1
1 is an encoder which adds an error correction code P, a synchronization code S, address data A, etc. to the image data D to form an error correction code block. 12 is a modulator which modulates the digital code into a signal that is easy to record on a magnetic tape. 613 is a VTR running system, which records and reproduces signals on a tape using a 4-channel magnetic head in the figure. A demodulator 14 inversely converts the reproduced signal into a digital code. 15 is a decoder which separates image data and an error correction code based on a synchronization code, separates a code error generated in a VTR from a correction code, and
Correct code errors that occur in TR. 16 is a channel synthesis circuit which combines the codes of 44 channels into one code, which is converted into an analog television signal by a D/A converter 17 and outputted to a terminal 18.

In the decoder 15, it is necessary to detect the synchronization code from the reproduced code. FIG. 6 shows an embodiment in which a synchronization code is detected without error. A reproduced code is given to the terminal 19 by the demodulator 14 . Reference numeral 2o denotes a slam detection circuit, which generates a pulse when a predetermined synchronization pattern is detected. As shown in FIG. 7(a), this pulse may occur at a position other than the original synchronization code, or may not occur at the position of an original synchronization code.

21 is an AND gate that blocks pulses generated at positions other than the original synchronization code position. That is, 22 is a gate signal generation circuit, and when a pulse is output to the AND gate 21,
Thereafter, the inhibit signal (b) is generated for a slightly shorter period than one original synchronization code interval. As a result, as shown in (Q), the synchronization code erroneously detected during the image data period is
It does not appear at the output of gate 21.

On the other hand, a counter 24 counts the clocks applied to the terminal 23 by a number corresponding to the original synchronization code interval. When the counter 24 is reset with the pulse that detects the synchronization code, a pulse is obtained at the output of the counter 24 at the time when the synchronization code should originally be detected. If the outputs of the AND gate 21 and the counter 24 are mixed by the OR gate 25, a detection pulse is always obtained at the terminal 26 at the time when the synchronization code should normally be detected, as shown in FIG. 7(d).

The embodiment of synchronization code detection shown in FIG. 6 also functions effectively when the tape speed is the same during recording and playback.

That is, as shown in FIG. 1, the track on the tape consists of synchronization code blocks, and when the head plays this track, synchronization codes are obtained at regular intervals.

On the other hand, if synchronization code blocks are lined up between adjacent tracks as in the present invention shown in FIG. Even when the head reproduces, the reproduced synchronization codes are at regular intervals. As a result, the synchronization code detection shown in FIG. 6 operates effectively.

In the example shown in FIG. 1, a case has been described in which each track is recorded with a single azimuth angle of the same azimuth angle. However, the present invention can also be applied when the azimuth angle of the head differs between tracks. Suppose that two types of heads with different azimuth angles are used, and the azimuth angle is the same for every other track (that is, the azimuth angle is different from that of the adjacent track). Naturally, two types of heads are used during reproduction, but in this case, only signals of tracks having the same azimuth angle can be obtained from one head. If there are two types of heads, 1
Since the signal is reproduced every track, that is, every two tracks, the condition that synchronization code blocks should be lined up every two tracks can be obtained by replacing Q in equation (3) with 2Q.

Generally, if recording is performed at the same azimuth angle every N tracks, Q may be set to NQ.

〔Effect of the invention〕

According to the present invention, by recording a digitally encoded television signal such that synchronization code blocks are arranged between adjacent tracks having the same azimuth angle, reproduced synchronization codes can be obtained at regular intervals regardless of the tape playback speed. Because it is possible to
It becomes possible to predict the detection time of the next synchronization code, which has the effect of preventing erroneous detection of synchronization codes.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams showing the principle of the present invention, and Figures 5 to 7.
The figures are a device configuration diagram and a signal diagram showing an embodiment of the present invention. 1...Tape, 2...Synchronization code block, 3-7.
...Playback head trajectory, 8, 18, 19, 23.26...
・Terminal, 9... A/D converter, 10... Distribution circuit, 11... Encoder, 12... Modulator, 13...
- VTR running system, 14... demodulator, 15... decoder, 16... synthesis circuit. 17... D/A converter, 20... Bang detection circuit,
21...A, ND gate, 22... Gate signal generation circuit, 24... Counter, 25... OR gate.

Claims (1)

[Claims] A digital image recording and reproducing apparatus characterized in that an image signal is converted into a digital code and recorded so that the boundaries of code blocks containing synchronization codes are lined up between adjacent tracks having the same azimuth angle.