JPH0614726B2 - Video signal recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to variable speed reproduction of a video signal recording / reproducing apparatus (hereinafter referred to as VTR) which employs a multi-channel, multi-segment recording system.

[Conventional technology]

Conventionally, the high quality image of variable speed reproduction of a VTR adopting a recording method (1 channel 1 segment recording method) for recording a 1-field video signal on a single track on a magnetic tape is required for high precision tape running control and special It has been realized by adopting a reproducing head. Further, with the recent trend toward lower prices of semiconductor products such as memories and higher speeds and higher densities, a field memory is provided in the VTR so that variable speed reproduction can be performed well.

The variable speed reproduction using the field memory will be described below. FIG. 3 shows a variable speed reproduction system of a VTR using a field memory. (1) is a recorded magnetic tape, (100)
a) and (100b) are rotary heads with different azimuths,
(101a), (101b) are rotary heads (100a),
A head amplifier for amplifying the output of (100b), (102) a switching circuit for selecting one of the outputs of the head amplifiers (101a), (101b), and (103) performing FM demodulation to obtain a video signal. A video signal processing circuit that also detects a synchronization signal, (104) is a field memory, and (105) is a reproduction F.
An envelope detection circuit for extracting the envelope of the M signal, (106) a comparator for comparing the output of the envelope detection circuit (105) with a predetermined level, and (107) a synchronization signal output from the video signal processing circuit (103). A memory control circuit that controls writing in the field memory (104) based on the output of the comparator (106) and performs reading control asynchronously with the synchronization signal.

Further, (10) is a control head, (11) is a CP motor, (12) is a motor driver for driving the CP motor (11),
Reference numeral (13) is a traveling control circuit for controlling the motor driver (12).

Next, the operation will be described. M speed (M = ± 2, ±
4, ± 6 ...: ± indicates the traveling direction. + Indicates the same direction as normal reproduction, and-indicates the opposite direction. The case of performing high-speed reproduction of) will be described. When M = 6, the relationship between the recording track and the head scanning locus is as shown in FIG. In the figure,
R and L on the track are heads (100a) and (10
0b) or recorded by a head having the same azimuth. What is reproduced by each head due to the azimuth effect is the signal of the portion where the track is shaded. Comparator circuit (106)
Then, the output of the envelope detection circuit (105) is compared with a predetermined level, and a signal indicating the magnitude relationship is output to the memory control circuit (107). The memory control circuit (107) operates so as to write the output of the video signal processing circuit (103) in the field memory (104) when the output of the envelope detection circuit (105) is equal to or higher than a predetermined level. Therefore, in the field memory (104), the video signal for one field is recorded in the pattern of FIG. 4 (b).

On the other hand, there is a high-definition TV system that has recently been developed and put into practical use as a next-generation TV system. The video signal band of the high-definition TV system is a wide band of about 20 MHz. As a means for recording such a wide band signal, there is a method of adopting a multi-channel multi-segment recording system. That is, by increasing the number of channels, the signal bandwidth per channel is reduced, and by increasing the number of segments, the relative speed between the rotary head and the magnetic tape is increased and the recording wavelength is lengthened, so that the conventional magnetic recording technology achieves a wide band. It is intended to record and reproduce signals.

The case of using the 2-channel 3-segment recording method will be described below. Input video signal (1 channel composite signal) is set in units of 1 horizontal scanning period (hereinafter abbreviated as 1H), and 2 channels (each are CH.A, CH.
B)) and the time axis is doubled. As a result, the signal bandwidth of each channel is halved.

FIG. 5 (a) shows the arrangement of the rotary heads. (2
2) is a rotary drum, (2a) and (2b) are rotary heads for recording and reproducing CH.A signals, and (3a) and (3b) are rotary heads for recording and reproducing CH.B signals. Rotating heads (2a) and (3a) and (2
b) and (3b) are arranged adjacent to each other. Also, record and
During reproduction, the magnetic tape is tightly wound around the rotating drum (22) by 180 °. The rotary drum (22) is 1.
Rotate 5 times. Therefore, 1 field video signal is CH.A, C
Both HBs are divided into 3 pieces (3 segments) for recording. FIG. 5 (b) is a conceptual diagram of the 2-channel 3-segment recording system, and FIG. 5 (c) shows a recording track pattern formed on the magnetic tape (1). A1, A2, and A3 shown on the tracks represent video information of the first, second, and third segments recorded by the heads (2a) and (2b) for channel A, respectively.

Here, consider high-speed reproduction in which the tape running speed is an integral multiple as in the past. When M = 2, the relationship between the recording track and the scanning locus of the head is as shown in FIG. 6 (a).

The case where the heads (2a), (2b) and (3a), (3b) have the same azimuth will be described. Since the azimuth effect does not appear, it is possible to reproduce the video signals of all the tracks on which the head lies.

On the other hand, the head (2a),
There is a section in which the data recorded in (2b) and the data recorded in heads (3a) and (3b) are read at the same time. In this portion, the video signals overlap with each other, and a good output cannot be obtained.

Considering the above, the output envelope of CH.A of the first segment is shown in FIG. The shaded areas overlap each other and a good screen cannot be obtained. FIG. 3D shows an actual screen. The shaded portion shows that the fixed nozzle band is generated without rewriting the image information in the field memory. If such a fixed noise band occurs, a problem that a visually good screen cannot be obtained occurs.

[Problems to be solved by the invention]

Therefore, although the field memory is used, the VT adopting the multi-channel multi-segment recording method
In the case of R, there was a problem that a video image could not be obtained because a video signal was missing during variable speed reproduction.

The present invention has been made to solve the above problems, and an object thereof is to realize good high-speed reproduction using a field memory.

[Means for solving problems]

The VTR according to the present invention is configured such that the tape running speed during variable speed reproduction is (N + m / M) times that during recording. Here, N, M, and m are integers, N = 1, ± 2, ± 3, ... M = 2,3,4, ... There is no integer r that satisfies (N + m / M) * M * k = r * S (where k = 1, ..., S-1), where M> m. Also, M and m are relatively prime.

[Action]

With the above configuration, in the variable speed reproduction of the VTR of the multi-channel multi-segment recording system, by appropriately selecting the running speed of the tape, it is possible to obtain a good variable speed reproduction screen in which the S / N is not lowered and the fixed noise band does not occur.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (1) and (10) to (13) are the same as those in FIG. (2a), (2b) and (3a), (3b) are rotary heads with different channels, respectively (4a), (4b)
Is a head amplifier, and the video signal processing circuits of (5a) and (5b) are F
M demodulation is performed to obtain a video signal, a sync signal is detected, and A / D conversion is performed. (6) is a field memory,
(7a) and (7b) are envelope detection circuits, (8a) and (8b) are comparators, (9a) and (9b) are video signal processing circuits (5a) and (5b).
This is a memory control circuit that controls the writing of the field memory (6) based on the synchronizing signal output from the comparator and the outputs of the comparators (8a) and (8b), and performs the reading control asynchronously with the synchronizing signal. (30a) and (30b) are memories for storing the data recorded in CH.A and CH.B, respectively. These two memories (30a) and (30b) are field memories.
(6) is composed.

Next, the operation will be described. As an example, consider a case where the tape running speed is (3 + 1/4) times that at the time of recording and a 2-channel 3-segment recording system is adopted. Head (2a),
(2b) and (3a), (3b) shall have the same azimuth.

Similar to the conventional example, the relationship between the recording track and the head scanning locus is as shown in FIG. Since the same azimuth is used, similar to the conventional example, the reproduced video signals overlap with the reproduced signals from the adjacent tracks shown by the hatched portion in FIG. 2 (b). Comparator to prevent overlapping
Adjust the width of (8a), (8b) and the guard band appropriately.
Considering that the relationship between the track pattern and the head locus is repeated with a period of 4 field periods, the output envelope of the first segment of CH.A is the same as the above, as shown in FIG.
Shown in.

Reading from the field memory (6) is performed asynchronously with the writing operation. As shown in FIG. 2 (c), the output level of the reproduced video signal stored in the field memory (6) is relatively high, and the S / N of the read video signal is high.
Is not so bad as to make the screen unsightly. Further, since all the data is rewritten twice every four fields, a fixed noise band does not occur, and extremely good high speed reproduction can be realized.

In this case, either head (CH.A or C
Pay attention to the video signal output from HB). For example CH.A
Consider only the output of. From the relationship between the track pattern and the head scanning locus in FIG. 2 (a), the CH.A emperobe diagram in the 4-field period is shown in FIG. 2 (d). The shaded area is CH.
It is the output envelope of the first segment of A. The figure (e) is obtained from this. From this, it can be seen that the same performance as above can be obtained by using only one channel.
This has the effect that the signal processing to be written in the field memory (6) can be made relatively simple.

In the above embodiment, (3 + 1/4) times the speed is shown as an example of the case where the 2-channel 3-segment recording system is adopted, but even when the multi-channel multi-segment recording system is adopted, the tape running speed at the time of recording is Of speed (N + m /
The same effect can be obtained by appropriately selecting the M) times speed.

Further, in the above-described embodiment, the case where azimuth recording is performed is performed, but the same effect can be obtained when different channels have different azimuth heads.

However, N, M, and m are integers, and N = 0, ± 1, ± 2, ± 3 ... …… M = 2,3,4 ………… m = 1,2,3 ………… M> m M and m are relatively prime. Further, when the tape running speed is determined, if the number of segments is S, in the range of S ≧ 2 N: integer M: 2,3,4 ......... m: 1,2,3 ......... M> m k: 1,2,3 ........... It seems that there is no integer r satisfying the relation of S-1. To decide.

If each channel has the same azimuth, the following conditions must be satisfied in addition to the above conditions. Letting the number of channels be L, an integer M that satisfies the relationship of L ≠ M is determined.

The restrictions on the determination of the tape running speed are as follows. VTR that generally adopts S segment recording method
In (N + m / M) times speed variable speed reproduction, the contents in the field memory are rewritten at M field cycles. However, the above conditions are met (ie If there is a natural number r such that Next to Before all the contents of the video signal are rewritten, it returns to the beginning and a fixed noise band occurs, so that a good variable speed reproduction screen cannot be obtained. Further, if all the heads have the same azimuth, the video signals overlap each other as described above, and the output envelope as shown in FIG. 6 (b) is obtained in one scanning period. Here, when M is determined so that L = M, a position where a good envelope is output stands at the same position as the next one scanning period, and the next one scanning period .... As in the above case, the signal is lost and a fixed noise band is generated, so that a good transmission raw screen cannot be obtained.

Further, although the proof is omitted, in the above embodiment, as an example in the case of adopting the 2-channel 3-segment recording system (3
+1/4) double speed, but in high-speed playback when the multi-channel multi-segment recording method in which each channel has the same azimuth, the tape running speed satisfies the above conditions, M = 2 × j × If L (L is the number of channels, j = 1, 2) is set, high-speed reproduction can be performed by using only one channel.

〔The invention's effect〕

As described above, according to the present invention, the tape running speed at the time of high-speed reproduction is (N + m / M) times (N is an integer other than O and 1, m and M are positive integers, and M> m) times the recording speed. Since I tried to get high-speed playback images using the field memory,
There is an effect that it is possible to perform excellent variable speed reproduction without an extreme decrease in S / N or fixed noise band.

[Brief description of drawings]

FIG. 1 is a block diagram of a video recording / reproducing apparatus according to an embodiment of the present invention, FIGS. 2 (a) to 2 (e) are operation explanatory diagrams of the invention apparatus, and FIG. 3 is a conventional one-channel one-segment system. Block diagram of the video recording / playback device that adopted the TD, Fig. 4
(a) and (b) are operation explanation diagrams of the conventional video recording / reproducing apparatus.
The figure is a conceptual diagram of 2 channel 3 segment recording system, 6th
The figure is an explanatory diagram of the operation when the 2-channel 3-segment recording system is used. In the figure, 1 ... magnetic tape, 2a, 2b ... rotary head (CH.A), 3a, 3b ... rotary head (CH.B), 5a, 5b ...
Video signal processing circuit, 6 ... Field memory, 7a, 7b
...... Envelope detection circuit, 8a, 8b …… Comparator,
9a, 9b …… Memory control circuit, 13 …… Running control circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A video signal is divided into a plurality of (S) segments for azimuth recording, and at the time of high speed reproduction, at least a reproduction signal from a recorded tape is synchronized with a synchronization signal detected from the reproduction signal. In a video signal recording / reproducing apparatus that writes a 1-field video signal in a memory capable of storing the video signal and reads the written content asynchronously with the synchronization signal, the tape running speed at the time of high-speed reproduction is defined as Condition 1
A video signal recording / reproducing apparatus comprising a traveling control circuit for controlling (N + m / M) times to satisfy 3 to 3. Condition 1 N is an integer other than O and −1 Condition 2 m and M are mutually positive positive integers, and m <M Condition 3 (N + m / M) × M × k = r × S There is an integer r that satisfies S No (k = 1, ..., S-1) 2. An L channel S segment (S ≧ 2, L ≧
2) The video signal recording / reproducing apparatus according to claim 1, wherein M ≠ L when the recording system is adopted and the rotary heads of the respective channels have the same azimuth angle.