JPS61247181A - Digital vtr - Google Patents

Abstract

PURPOSE:To improve the picture quality by moving a prereading rotary head in the direction of height and bringing the rotary head close to a reproduction rotary head at the variable speed reproduction to increase the reproduced data quantity at the variable speed reproduction. CONSTITUTION:In the digital VTR where other rotary heads 3A, 3B used as prereading heads at edition are provided in addition to normal reproduction rotary heads 2A, 2B, the heads 3A, 3B are provided to piezoelectric elements 7A, 7B so as to be moved in the direction of height. The said prereading heads 3A, 3B are moved near the reproduction rotary heads 2A, 2B at the variable speed reproduction. Since the reproduced data of the same field is obtained from both the reproduction rotary heads 2A, 2B and the advance read heads 3A, 3B at the variable speed reproduction, the data quantity at the variable speed reproduction is increased to improve the picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a helical scan type digital VTR, and particularly to a technique for improving variable speed playback thereof.

[Summary of the invention]

In addition to the normal playback rotary head, this invention provides a digital digital camera having a so-called look-ahead rotary head that reproduces a tape position that is at least 1 field (1 frame) ahead of the recording rotary head during editing. In a VTR, this rotary head for read-ahead is provided on a piezoelectric element so that it can move in the height direction perpendicular to the rotation direction, and during variable-speed playback, the rotary head for read-ahead on the voltage element is mounted on a drum for normal playback. By arranging the position close to the rotating circumferential surface of the rotary head to be the rotating circumferential surface, more data in the same field (frame) can be obtained from two sets of rotary heads for reproduction. The aim is to improve the playback quality.

[Conventional technology]

Some digital VTRs have a rotary head device as shown in FIG.

In the figure, (IA) and (IB) are rotary heads for recording, which are fixedly attached to the rotary drum (5). (2A) (2B) is a first reproducing rotating head, which is also fixedly attached to the rotating drum (5).

(3A) (3B) is the second reproducing rotary head for pre-reading, which is the head (IA) (I
B) and (2A) are installed at positions shifted in the height direction from (2B). In this case, the amount of deviation d
indicates the tape position that is more than 1 field ahead of the recording rotary head (IA) (IB).
(3B) is assumed to be scanning.

(4) is a rotary head for erasing.

The heads (LA) (2A) (3^) are made to have the same navel mass angle, and the heads (IB)
(2B) and (3B) are also made to have the same azimuth angle, but the azimuth angles are different between the head (18) (2A) (3A) and the head (IB) (2B) and (3B). This aims to eliminate crosstalk from adjacent tracks at the same time. If there is a wide guard band between the trunks and crosstalk between adjacent tracks is not a problem, there is no need for different azimuth angles.

In addition, in this example, the head (IA) (1B) and the head (3A) (3B) are arranged at a circumferential interval of 180° from each other, and the head (2^) (2B) and the head (4) are also arranged at a circumferential interval of 180° from each other. They are arranged at circumferential intervals of about 180°. Further, the heads (IA) (IB) and the head (4) and the heads (2A) (2B) and the heads (3A) (3B) are arranged at circumferential intervals of, for example, about 60° from each other.

For such a rotating head device, the magnetic tape (6) is wound diagonally around the drum in an Ω-shape over an angular range of approximately 300°, and the rotating drum (5) rotates twice in one field in the direction of the arrow. It can be rotated by a percentage.

During recording, after two tracks are erased in advance by the erasing rotary head (4), two tracks are erased per rotation by the solid rotary heads (IA) (IB).
Digital video signals are recorded by forming successive tracks. Therefore, video data for one field is divided into four tracks Tx, T2 + as shown in FIG.
They are recorded sequentially as T3 and T4. In this case, the digital video signal to be recorded is as follows.

That is, first, an analog video signal is sampled and converted to digital data, the data in the first half of one field of this digital data is scrambled, and the scrambled data is divided into blocks consisting of multiple samples. After address data and redundant bits for error correction are added in block units, the head (IA) is
(IB) is recorded as two tracks T1 and T2.

Next, the data in the second half of one field is scrambled in the same way and made into blocks, and address data and error correction codes are added to each block.
During the next one rotation period, the heads (IA) (IB) record the data as two tracks T31T4.

Address information includes data indicating which block of data for one field the block is, as well as
Frame and field information are written. As field information, numbers 0 to 7 are cyclically written for each field.

Reproduction is normally performed using the first reproduction rotary head (2A) (2B
), and this reproducing rotary head (2A)
The playback data from (2B) is de-scrambled,
Error correction processing is performed, the signal is converted back to an analog video signal, and the reproduced image is displayed on the screen of a monitor receiver.

Heads (38) and (3B) are used as so-called pre-read heads, especially during editing.

That is, as mentioned above, the head (3A) (3B
) is shifted in the height direction so as to lead the head (IA) (IB) by one field period or more.
Therefore, the track to be recorded can be reproduced one field or more ahead of the recording by the heads (IA) (IB).

This was done because of the following requirements.

For example, in insert a collection or assembly editing, the frame and field information in the data of the recording trunk must be continuous even after editing, so the frame and field information in the original recording track before editing must be the same. The frame of the recording track after editing needs to be the field information.

Therefore, the preread head (3A) (3B) reproduces frame and field information from the track to be recorded from now on, and the head (IA) (IB) records this frame and field information in that one rack. Add it as address data of block data.

Also, as mentioned above, one field is recorded as four tracks, so if you want to rewrite only the necessary part in one field unit, use this preread head (3A).
(3B), it is necessary to perform rewriting after completely reproducing one field. Therefore, this head (3B) is required.
A) (3B) is mounted so as to be shifted in the height direction so as to precede the heads (IA) and (IB) by one field or more.

[Problem that the invention seeks to solve]

By the way, when performing variable speed playback such as 3x speed, 5x speed, and 1/2x speed in the digital VTR as described above,
The rotary head scans across a plurality of trunks, and if a block address can be reproduced, a reproduced image can be obtained by writing the block data into the field memory accordingly. In this case, in order to obtain a reproduced image of high quality, it is desirable that as many blocks of data in the same field as possible be written into the field memory. Therefore, head (2A) (2B)
It is preferable if not only the reproduction output of the heads (3A) and (3B) can be used. However, as mentioned above, since heads (3A) and (3B) are used as look-ahead heads, they are shifted in the height direction so that they are at least l fields ahead of heads (IA) and (IB). Therefore, the head (2A)
(2B) is further advanced, and the center position of the scanning locus during one rotation period is a scanning position that is more than 1 field away, as shown by the arrow in FIG.

For this reason, four rotating heads (2A) (2B)
Even if the reproduction output from (3^) (3B) is obtained during variable speed reproduction, information in the same field cannot be obtained at the same time, so two sets of reproduction heads (2^) (2B
) and (3A) The output information of (3B) could not be used effectively.

[Means for solving problems]

This invention provides a digital VTR having a rotary head for pre-reading in addition to the rotary head for playback as described above, in which the rotary head for pre-reading is mounted on a piezoelectric element so as to be movable in the height direction, and during variable speed playback. The rotating circumferential surface of the rotary head on this piezoelectric element is arranged in the vicinity of the rotating circumferential surface of the reproducing rotary head.

C effect] During variable speed reproduction, the reproducing rotary head and the pre-reading rotary head are at close scanning positions, so that the reproduced data from these two sets of rotary heads can be effectively obtained as the reproduced data in the l field, and this The number of data processors written to field memory.

increases, and an improvement in the image quality of the reproduced image can be expected.

〔Example〕

FIG. 1 is a diagram showing the arrangement in the height direction of the rotary head used in the digital VTR according to the present invention.
(7B) Mounted on the top and made movable in the height direction.

In addition, in this example, in order to minimize the swing width of the bimorph plates (7A) (7B), the voltage supplied to the bimorph plates (7A) (7B) is zero, and the amount of displacement is zero (there is no residual displacement). (assumed, the same applies hereinafter), the position in the height direction is as follows: head (IA) (IB) and (
2A) The amount of deviation in the height direction with respect to (2B) is set to d/2, which is 1/2 of the conventional case.

That is, when the heads (2A) (2B) scan the track T as shown in FIG.
7A) If the displacement of (7B) is zero, the head (3A)
(3B) is in a state of scanning on the track T3 which is ahead by 1/2 field as shown in the figure.

When editing using the head (3A) (3B) as a read-ahead head, the bimorph board (7A) (7
For B), head (IA) (1B) (2A)
A voltage is applied in a direction that increases the amount of deviation in the height direction with respect to (2B), and the height positions of the heads (3A) and (3B) are shifted in the direction shown by the arrow (11) in FIG. ) Scan the tape position that precedes (IB) by one field or more, that is, by four tracks or more.

During variable speed playback, the bimorph plate (7A)
For (7B), head (1^) (IB)
(2A) Applying a voltage in the direction in which the amount of deviation in the height direction from (2B) becomes smaller, the height position of the heads (3A) (3B) is shifted in the direction shown by the arrow (12) in FIG. 2, The vicinity of the rotating circumferential surface of the reproducing head (2A) (2B) is the rotating circumferential surface. For example, in the case of 3x speed, the head (2A) (2B) is a solid line (13)
When scanning as shown in , the head (3A) (3B
) is scanned in the vicinity thereof as shown by the two-dot chain line (14).

Even during this variable speed playback, drum phase servo is applied to the rotary head up to a distance of 3 to 5 times by the playback signal CTL of the control signal recorded at the end of the width direction of the tape, so that Head (2A) (2B) and (
3^) (3B) is set to start scanning.

FIG. 3 shows an example of a reproduction system of a digital VTR according to the present invention.

Let's explain this playback system by taking as an example the case of triple speed playback in which the heads (2A), (2B), and (3^) (3B) scan as shown by arrows (13) and (14) in Fig. 2. .

Head (2A) (2B) and (3A) (3B)
The playback data picked up by the terminal (21) is sent to the address detection circuit (23) via the amplifier (22)
address data for each block is extracted, block address, field, and frame information are detected from this, and this is supplied to the memory controller (24). This memory controller (24) is also supplied with playback speed information formed from a playback control signal through a terminal (25), and is supplied from the memory controller (24) to a field memory (29).
(30) In addition to the address signal supplied to the switch circuit (
26), (27), and (28) switching signals are obtained.

Switches (27) and (28) are two memories (2
9) For (30), this is used to switch between the memory to write to and the memory to read from.The memory is switched alternately as shown in the figure so that writing and reading are not done at the same time. This is when a change in information is detected.

The video data passed through the address detection circuit (23) is then supplied to and written into the field memory (29) or (30) via the switches (26) and (27). In this case, 1 field memory (29) or (3
0), so that only one field of data is written to each block, and when data other than the field currently being written is reproduced, the switch (26) is turned off for the period of that block data. , and that data is excluded.

In this way, data in the same I field is written alternately into the memories (29) and (30), and reading is performed from the memory that is not in the writing state.

In this case, the data written in the memory (29) (30) is read out after the error is corrected in the error correction circuit (31), and when read out, it is descrambled and restored to the original state. Returned to digital data in order.

The data read out from the memory (29) (30) in this way is supplied to the D/A converter (32) via the switch (28) and returned to an analog video signal, which is led out to the output end (33). This is supplied to a monitor receiver, and the reproduced image is displayed on its screen.

In this case, the reproduction data supplied from the input terminal (21) is transmitted not only to the heads (2A) (2B) but also to the heads (3).
A) This is the data picked up by (3B). Moreover, since the heads (3A) (3B) scan the scan positions close to the heads (2^) (2B), the outputs of these two sets of heads concentrate on the same field.

Therefore, field memory (29) or (30)
The number of block data written to the recording head increases compared to when one set of playback heads is used, which greatly contributes to improving image quality.

In addition, in the above example, the pre-reading head (3A) (3
The position in the height direction when the displacement of the bimorph plate in B) is zero is set between the pre-read position and the position near the rotational surface of the heads (2A) (2B), so the swing width of the bimorph plate is , when the displacement of the bimorph plate is zero, it is approximately 1/2 compared to the case where the heads (3A) (3B) are arranged at the pre-reading position, and there is an advantage that the bimorph plate can be small.

〔Effect of the invention〕

According to this invention, in a device having a separate rotating head used as a pre-reading head during editing in addition to the normal rotating head for playback, this separate rotating head is provided on the piezoelectric element, and during variable speed playback, normal playback is performed. The rotary head rotates on a rotating surface near the rotating surface of the rotating head for playback, so that as much as possible of the same field of playback output as the playback output from the normal playback rotary head can be obtained from this other rotating head. Therefore, during variable speed reproduction, the amount of block data written to the field memory is greater than when only the output of the rotary head for reproduction is used, and an improvement in image quality can be expected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the positional relationship in the height direction of the rotary head used in the digital VTR according to the present invention, FIG. 2 is a diagram for explaining the scanning position of the rotary head, and FIG. 3 is a diagram showing the reproduction system of the present invention. FIGS. 4 and 5 are block diagrams for explaining an example of a rotary head device used in a digital VTR, and FIG. 6 is a diagram for explaining its recording track pattern and head scanning position. (l^”) (1B) is a recording rotating head, (2A)
(2B) is a rotating head for reproduction, (3A) (3B
) is a rotary head for pre-reading, and (7A) and (7B) are bimorph plates. 17 nord t! East Tora 1. Pattern diagram Figure 8

Claims (1)

[Claims] A video signal is digitized, and one field (one field) of the video signal is digitized.
Each frame of data is scrambled and divided into a plurality of blocks, and each block is recorded as a diagonal track with address data added, and this is played back. A first reproducing rotary head whose position in the height direction perpendicular to the rotation direction is fixed, and a rotary head mounted on the piezoelectric element, and when editing,
and a second reproducing rotary head positioned at a position shifted in the height direction so as to scan a tape position preceding the recording rotary head by one field (one frame) or more, and during variable speed reproduction, The digital VTR is configured such that the second rotary head is moved in the height direction by the piezoelectric element so as to scan a rotating circumferential surface near the rotating circumferential surface of the first rotating head.