JPH04326272A - Reproducing device - Google Patents

Abstract

PURPOSE:To enable satisfactory variable speed reproduction at a private VTR. CONSTITUTION:Regenerative signals from heads SP1, SP2, EP1 and EP2 are changed over at a switch circuit 2 and supplied to a reproducing circuit 4, and formed video signals are supplied through an A/D conversion circuit 5 to a field memory 6. On the other hand, an address reset signal to be formed at the position of a rotating phase corresponding to the vertical synchronizing signal of the video signal recorded by the heads SP1 and SP2, for example, from a servo circuit 7 is supplied to the field memory 6. Thus, the video signals are respectively stored at prescribed addresses, and these stored video signals are successively read out and extracted through a D/A conversion circuit 9 to an output terminal 10. Further, a head switch signal and an address reset signal are supplied to a memory control circuit 11 and the write control signal of the field memory 6 is formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a playback device for performing variable speed playback in, for example, a consumer VTR.

0002

2. Description of the Related Art For example, a consumer VTR is equipped with two sets of playback heads, one for standard playback and one for long-time playback, as shown in FIG. That is, in this device, SP1 and SP2 are standard playback heads, and EP
1. EP2 is a head for long-time playback. These heads SP1, SP2 and EP1, EP2 are attached at an angle of 180 degrees to each other in each group, and the two heads SP1, SP2 and EP1, EP of each group
2 are mutually positive and negative azimuth angles. Further, the heads EP1 and EP2 are mounted behind the heads SP1 and SP2 by, for example, about 1.4 degrees (a distance corresponding to two horizontal periods of the video signal to be recorded and reproduced), and the head SP1 has a positive azimuth angle. A head EP2 with a negative azimuth angle is provided after the head SP2, and a head EP1 with a positive azimuth angle is provided after the head SP2 with a negative azimuth angle.

In such an apparatus, when a still image is to be reproduced, for example, the scanning locus of the head relative to the recording track is as shown by the broken line in FIG. 6, for example. Here, with this scanning locus, for example, one field worth of signals marked with vertical lines can be reproduced with a head having a negative azimuth angle. Therefore, in this case, it is conceivable to perform still image reproduction using head SP2 and head EP2. However, in this case, two video signals are sent between the heads SP and EP as described above.
There is a time difference equal to the horizontal period. Therefore, if the reproduction signal remains as it is, the screen will move up and down for each field, making it impossible to perform good reproduction. In contrast, in the conventional apparatus, a pseudo vertical synchronization signal is inserted into the reproduced signal, and the insertion position is moved for each head SP2 and EP2 to eliminate the time difference.

However, in this device, for example, 1
In double speed playback, the scanning locus of the head relative to the recording track is, for example, as shown by the broken line in FIG. Here, in this scanning trajectory, for example, in the first half, a signal with horizontal lines can be reproduced by a head with a positive azimuth angle, and in the second half, a signal with vertical lines can be reproduced with a head with a negative azimuth angle. That is, in this case, reproduction can be performed by switching heads such that, for example, when the first half is head SP1, the second half is head EP2, and when the first half is head EP1, the second half is head SP2. However, in this case, there is a time difference of two horizontal periods of the video signal between the heads SP and EP as described above. In this case, when switching from head SP1 to head EP2, the signal is 2.
On the other hand, when switching from head EP1 to head SP2, the signal precedes by two horizontal periods.

[0005] Therefore, for example, a pseudo vertical synchronization signal is inserted into such a reproduced signal so that the first half heads SP1,
Even if the time difference between the signals from EP1 is eliminated, there will be a time difference of four horizontal periods between the signals from heads SP2 and EP2 in the second half, and the screen will move up and down, making it difficult to perform good playback. Can not. Note that the relationship between the azimuth angles may be opposite to that described above. Further, even in variable speed playback other than 1/2 speed, a similar time difference will occur if the head is switched as described above.

[0006] Conventionally, it has been proposed to provide an extra pair of wide heads with the same azimuth angle, separated by an angle of 180 degrees, to perform variable speed reproduction without switching the heads. However, this method requires a special head drum device, increasing manufacturing costs. Another problem is that only signals with the same azimuth angle are reproduced, and signals with different azimuth angles cannot be reproduced.

[0007]

[Problem to be Solved by the Invention] The problem to be solved by the invention is that when the head is switched during variable speed playback in conventional devices, a time difference occurs in the playback signal, making it impossible to perform good playback. .

[0008]

[Means for Solving the Problems] The present invention provides a first set and a second set of playback heads SP1 and SP that are mounted at different positions.
2, EP1, and EP2 are provided, and during variable speed playback, the playback signals from the first set and the second set of playback heads are switched and taken out (switch circuit 2), and the taken out playback signals are written in the memory 6. At the time of switching, writing to the memory is temporarily stopped (memory control circuit 11) according to the time difference due to the mounting position, thereby absorbing the time difference and obtaining a normal signal (output terminal 10). It is a device.

[0009]

[Operation] According to this, by temporarily stopping writing to the memory, the time difference due to the mounting position of the head is absorbed, and a good reproduction signal can be obtained even during variable speed reproduction.

0010

[Embodiment] In FIG. 1, from tape T to head SP1,
The signals reproduced at SP2, EP1, and EP2 are supplied to the switch circuit 2 through reproduction amplifiers 1S and 1E for each set. In addition, the signals from the reproduction amplifiers 1S and 1E are supplied to a level discrimination circuit 3 to discriminate the level of the reproduction signal, and this discrimination signal (head switching signal) is supplied to the switch circuit 2, and the level of the reproduction signal is higher. A signal is taken out from the switch circuit 2. The signal from this switch circuit 2 is supplied to a reproduction circuit 4 to form a video signal, and this video signal is supplied to a field memory 6 through an A/D conversion circuit 5.

A signal from the servo circuit 7 is also supplied to the drum motor 8 to drive the heads SP1, SP2, EP1, and E.
P2 is rotated at a predetermined rotational phase. At the same time, an address reset signal is generated from the servo circuit 7 at a rotational phase position corresponding to the vertical synchronization signal of the video signal recorded by the heads SP1 and SP2, and this signal is supplied to the field memory 6. As a result, the video signals converted by the A/D conversion circuit 5 are stored in the field memory 6 at respective predetermined addresses. The video signals stored in the field memory 6 are sequentially read out and taken out to the output terminal 10 through the D/A conversion circuit 9.

Further, the above-mentioned head switching signal and address reset signal are supplied to the memory control circuit 11 to form a write control signal for the field memory 6. Here, when the field memory 6 is supplied with an address reset signal and a write control signal as shown in B and C in the same figure in response to an input signal shown in A in FIG. The stored signals are sequentially read out.

For example, when the above-mentioned still image is being reproduced, the input signal supplied to the field memory 6 is as shown in A of FIG. Note that the figure shows signals for two fields, and v in the figure is vertical synchronization. On the other hand, the address reset signal and head switching signal are as shown in B and C in the figure. Therefore, in this case, as shown in D in the figure, a write control signal for, for example, two horizontal periods is generated after the address reset signal during the period in which the head switching signal is at a low potential. As a result, a signal as shown in E in the figure is stored in the field memory 6, and when this signal is read out, the time difference between fields is eliminated.

When variable speed reproduction is being performed, the input signal supplied to the field memory 6 is as shown in A of FIG. Note that the figure shows signals for two fields, and v in the figure is vertical synchronization. On the other hand, the address reset signal and head switching signal are as shown in B and C in the figure. In this case, as shown in D in the same figure, for example, a write control signal for two horizontal periods is generated after the address reset signal during the period in which the head switching signal is at a low potential, and at the same time the head switching signal falls. Afterwards, write control signals for, for example, four horizontal periods are formed. As a result, a signal as shown in E in the figure is stored in the field memory 6, and when this signal is read out, the time difference between fields is eliminated.

In these figures, it can be seen that the time difference has been eliminated because the waveforms of the two fields shown in E are equal. Also, the write control signal for four horizontal periods that is formed after the head switching signal falls during variable speed playback is formed in the same way during still image playback, but the address reset signal is formed immediately after that and becomes invalid. It is something. However, the time axis in the diagram is not accurate.

Thus, according to the above-mentioned device, by temporarily stopping writing to the memory 6 (memory control circuit 11), the time difference due to the mounting positions of the heads SP1, SP2 and EP1, EP2 is absorbed, and even during variable speed playback. It is possible to obtain a good reproduction signal (output terminal 10). Therefore, according to this device, good variable speed reproduction can be performed without using a special head drum device or the like.

[0017] In the above-mentioned apparatus, when the head is switched, the reproduced signal is compressed to some extent. For this reason, it is unsuitable for situations where a large number of head changes occur during one field, and is employed, for example, in so-called jog mode playback at double speed or lower. In addition, in the above-mentioned device, the length of the write control signal is set to the heads SP1, SP2 and EP1, respectively.
, which corresponds to the time difference depending on the mounting position of EP2.

[0018]

According to the present invention, by temporarily stopping writing to the memory, the time difference due to the mounting position of the head is absorbed, and a good reproduction signal can be obtained even during variable speed reproduction.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an example of a playback device according to the present invention.

FIG. 2 is a diagram for explaining the same.

FIG. 3 is a time chart diagram of still image playback.

FIG. 4 is a time chart diagram of variable speed reproduction.

FIG. 5 is a diagram for explaining the mounting position of the head.

FIG. 6 is a diagram showing a scanning locus of still image reproduction.

FIG. 7 is a diagram showing a scanning locus of variable speed reproduction.

[Explanation of symbols]

T Tape SP1, SP2 Standard playback head EP1, EP2 Long time playback head 1S, 1E
Reproduction amplifier 2 Switch circuit 3 Level discrimination circuit 4 Reproduction circuit 5 A/D conversion circuit 6 Field memory 7 Servo circuit 8 Drum motor 9 D/A conversion circuit 10 Output terminal 11 Memory control circuit 11

Claims (1)

[Claims] 1. A first set and a second set of playback heads installed at different mounting positions are provided, and during variable speed playback, the playback signals from the first set and the second set of playback heads are switched and extracted, and A playback device that absorbs the time difference and obtains a normal signal by writing the retrieved playback signal into a memory and temporarily stopping writing to the memory according to the time difference due to the mounting position when switching. .