JPS62256588A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain the original composite video signal of good S/N by compressing the amplitude of the synchronizing signal part of the composite video signal and extending the relative amplitude of a video signal part to perform FM recording and expanding the synchronizing signal part of a demodulated signal at the reproducing time. CONSTITUTION:The video signal part of a composite video signal A is directly supplied to a frequency modulator 13 from a preemphasis circuit 12 by switching of switches 15 and 16. The synchronizing signal part passes a compressor 17 from the preemphasis circuit 12 and is supplied to the frequency modulator 13, and the amplitude of the synchronizing signal part is compressed in the input signal C of the modulator 13. Since the amplitude of the video signal part is not changed, the overall amplitude of input signals of the modulator 13 is reduced by the compression of the synchronizing signal. Therefore, the modulation sensitivity of the modulator 13 is raised to keep a prescribed frequency shift, and a frequency shift corresponding to the video signal part is made large. Thus, the S/N of reproduced pictures is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording/reproducing device suitable for use in a video tape recorder or the like.

[Summary of the invention]

The present invention compresses the amplitude of the synchronization signal part of a composite video signal to increase the relative ti width of the video signal part, performs FM recording, and expands the synchronization signal part in the reconstructed signal during playback. This is to obtain a good original composite video signal of /N.

[Conventional technology]

In a conventional video tape recorder (VTR), during recording, the recording system input terminal (11
), the composite video signal from the pre-emphasis circuit (12
) is supplied to the frequency modulator (13), and a carrier wave of a predetermined frequency is frequency-modulated. The FM-RF multiplied signal of a predetermined frequency bandwidth outputted from the modulator (13) is supplied to the magnetic head H via a high-pass filter (14), a recording amplifier and a recording/reproduction changeover switch (not shown), and is supplied to the magnetic head H. Recorded on magnetic tape with no .

During playback, the playback FM-RF signal from the magnetic head 11 is passed through a preamplifier and a recording/playback switch (not shown) to a high-pass filter of the playback thread as shown in FIG.
(21), and the output of the high-pass filter (21) is fed to a demodulator (22). The composite video signal output from the 1M modulator (22) is pre-emphasized in the same way as the input to the modulator (13), and this is subjected to de-emphasis processing with characteristics opposite to pre-emphasis in the de-emphasis circuit (23). In response, the original composite video signal is reproduced and delivered to the output terminal (24).

[Problem that the invention seeks to solve]

As mentioned above, in conventional VTRs, pre-emphasis and de-emphasis are performed before and after frequency modulation and demodulation to improve the S/N of reproduced images.

By the way, in the conventional VTR, since the frequency bandwidth of the FM-RF signal is specified, the amplitude of the input signal to the modulator (13) cannot exceed a predetermined value.

However, the input to this variable L'5 (13) is a pre-emphasized composite video signal, and since the synchronization signal portion occupies a considerable proportion of the total amplitude, the video signal that directly contributes to the reproduced image is It is not possible to increase the amplitude of this part. Therefore, the FM-
There is a problem in that it is not possible to take a large frequency shift corresponding to the video signal portion of the RF signal, and the S/N of the reproduced image is not necessarily sufficient.

In view of this, an object of the present invention is to increase the S of the reproduced image by increasing the frequency shift corresponding to the video signal portion.
An object of the present invention is to provide a recording/reproducing device with improved /N.

[Means for solving problems]

The present invention supplies a composite video signal to a pre-emphasis circuit, compresses the amplitude of a sync signal portion output from the pre-emphasis circuit compared to a video signal portion, and combines the compressed sync signal portion and video signal portion. is supplied to the frequency modulator for recording, and at the time of playback, the amplitude of the synchronizing signal part output from the demodulator is expanded compared to the video signal part, and the expanded synchronizing signal part and the video signal part are de-emphasized. This is a recording and reproducing device that supplies the signal to a circuit to obtain an original composite video signal.

[Effect]

According to this configuration, the relative amplitude of the video signal portion input to the frequency modulator becomes large, and the corresponding FM-
The RF multiplied signal frequency deviation increases, and the S of the reproduced image
/N improves.

〔Example〕

Hereinafter, an embodiment in which a recording/reproducing apparatus according to the present invention is applied to a VTR will be described with reference to FIGS. 1 and 2.

FIG. 1 shows the configuration of an embodiment of the present invention.

In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals and redundant explanation will be omitted.

In FIG. 1, electronic changeover switches (15) and (16) and a compressor (17) are provided between the pre-emphasis circuit (12) and the frequency modulator (13), and
Electronic changeover switches (25) and (26) and an expander (27) are provided between the demodulator (22) and the de-emphasis circuit (23).

The output of the pre-emphasis circuit (12) is connected to the switch (15).
) is supplied to the movable contact (15c). Switch (15
) and (16), each video side fixed contact (15ν) and (1
6v) is directly connected, and each synchronous side fixed contact (
A compressor (17) is connected between 15g) and 16s, and the output of the movable contact (16c) of the switch (16) is supplied to the frequency modulator (13).

The output of the demodulator (22) is connected to the movable contact (
25c). Switches (25) and (26)
) are directly connected to each video side fixed contact (25V) and (26S), and each synchronization side fixed contact (25S)
An expander (27) is connected between and (26s), and the output of the movable contact (26c) of the switch (26) is supplied to the de-emphasis circuit (23).

Each switch (15), (16), (25)
and (26), the output of the control pulse generator (30) is supplied as a control signal.

The operation of the first (2I) embodiment is as follows. During recording, an emphasized composite video signal as shown in FIG. 2A is sent from the pre-emphasis circuit (12) to the switch (
15). In addition, as shown in FIG. B, the control pulse ■ falling during the front porch period and rising during the back porch period of the horizontal synchronizing signal of this composite video signal ■ is sent from the pulse generator (30) to both switches (15) and (16)
supplied to When the control pulse ■ is "I+1", contrary to the illustration, the movable contacts (15c) and (16c) of both switches (15) and (16) are connected to the video side fixed contacts (15v) and (16v), respectively. When connected and the control pulse ■ is “Lo”, each movable contact (15c)
and (16c) are each synchronous side fixed contact (15s)
and (16s).

By the switching operations of both switches (15) and (16) as described above, the video signal portion of the composite video signal (2) is directly frequency modulated from the pre-emphasis circuit (12)! 5 (13
). On the other hand, the synchronization signal portion is supplied from the pre-emphasis circuit (12) to the frequency modulator (13) via the compressor (17). Therefore, the amplitude of the synchronizing signal portion of the input signal ◎ to the modulator (13) is compressed, as shown in FIG. 2C. Furthermore, since the amplitude of the video signal portion does not change, the total amplitude of the input signal to the modulator (13) is reduced by the amount by which the synchronization signal is compressed. At this rate, FM-R
Since the F-fold signal frequency deviation also decreases, in this embodiment, the modulation sensitivity of the modulator (13) is increased to maintain a predetermined frequency deviation, and accordingly, the frequency deviation corresponding to the video signal portion is increased. A large frequency deviation is taken.

During reproduction, the demodulator (22) supplies the switch (25) with a demodulated I-frequency signal that is equal to the input signal ◎ of the modulator (13) as shown in FIG. 2C. In addition, in the same way as during recording, the control pulse () which falls during the front porch period of the horizontal synchronizing signal of this demodulated signal and rises during the back porch period is pulse generated from J5 (30) to both switches (25) and (26). In the case of the control pulse ("Ili"), contrary to the illustration, each movable contact (25c) and (26c) of both switches (25) and (26) is connected to each image side fixed contact ( 25v ) and (26v ), and when the control pulse ■ is "Lo", each movable contact (
25c) and (26c) are connected to the respective synchronous side fixed contacts (25s) and (26s), respectively.

By switching the switches (25) and (26) as described above, the video signal portion of the demodulated signal O is sent to the demodulator (22).
is directly supplied to the de-emphasis circuit (23). On the other hand, the synchronization signal part is transmitted from the demodulator (22) to the expander (22).
7) and is supplied to the de-emphasis circuit (23). Therefore, in the input signal (2) of the de-emphasis circuit (23), the amplitude of the compressed synchronization signal portion is restored, as shown in the second diagram.

- During reproduction, even though the reproduction RF signal of the magnetic head H is at the same level as the conventional one, in this embodiment, as described above,
Since the frequency shift corresponding to the video signal portion in the M-RF signal is large, the amplitude of the video signal portion output from the demodulator (22) becomes large. On the other hand, since the noise level is approximately constant depending mainly on the signal bandwidth,
N is improved.

Next, referring to FIG. 3 and FIG.
Another example applied to R will be described.

The structure of another embodiment of the present invention is shown in FIG.

In FIG. 3, parts corresponding to those in FIGS. 1 and 5 are designated by the same reference numerals, and redundant explanation will be omitted.

In Figure 3, (18) is a voltage controlled amplifier, (29)
are voltage controlled attenuators whose respective gain or attenuation is controlled by control pulses provided by a pulse generator (30). The output of the pre-emphasis circuit (12) is supplied to the frequency modulator (13) via the voltage controlled amplifier (18) and the attenuator (19), and '1! i
The output of the modulator (22) is supplied to a de-emphasis circuit (23) via an amplifier (28) and a voltage controlled attenuator (29).

The operation of the embodiment of FIG. 3 is as follows.

During recording, from the pre-emphasis circuit (12), Fig. 4A
An emphasized composite video signal as shown in FIG. 1 is supplied to a voltage controlled amplifier (I8). In addition, as shown in FIG.
8). When control pulse ■ is “Ili”,
The gain of the voltage control amplifier (18) is a predetermined value, for example, twice, and is 1 when the control pulse ■ is "Lo".
It will be doubled.

Therefore, in the voltage control amplifier (18), C
As shown in FIG. 2, the amplitude of the video signal portion is amplified by twice (for example, twice), and the amplitude of the synchronizing signal portion is transmitted without changing. The output signal ◎ of this voltage-controlled amplifier W (18) is supplied to an attenuator (19), and as shown in the figure, its amplitude is attenuated to 1/K (for example, l/2), and the input signal of a predetermined amplitude is The signal ■ becomes the frequency modulator (13
). Therefore, the FM-RF multiplied signal output from the modulator (13) is kept at a predetermined frequency deviation, and the frequency deviation corresponding to the video signal portion is set large.

During reproduction, a signal equal to the input signal ■ of the modulator (13) as shown in the fourth diagram is sent from the demodulator (22) with a gain equal to or times (
For example, the signal is supplied to an amplifier (28) whose amplitude is doubled (for example, 2 times), and the amplitude is amplified by twice (for example, 2 times) as shown in FIG. The output signal [F] of this amplifier (28) is supplied to a voltage controlled attenuator (29).

Also, as shown in Figure B, a control pulse ■ is generated that falls during the front porch period of the horizontal synchronizing signal of the demodulated signal and rises during the back porch period! (30) to the voltage controlled attenuator (29). When the control pulse ■ is “11 bits”, the attenuation degree of the voltage controlled attenuator (29) is, for example, 1/
It becomes a predetermined value 1/, such as twice, and the control pulse ■ becomes Lo
”, it becomes 1 times.

Therefore, in the voltage controlled attenuator (29), F
As shown in , the amplitude of the video signal portion is attenuated to 1/2 times (for example, 1/2 times), and the width of the synchronizing signal portion is transmitted without changing.
The input signal [F] of 23) is equal to the output (2) of the pre-emphasis circuit (12) as shown in A of the figure.

Also in this embodiment, since the frequency shift corresponding to the video signal portion in the FM-RF signal is large, the S/N of the reproduced video signal and, by extension, the p-raw image is improved.

The embodiments in which the present invention is applied to a VTR have been described above, but the present invention can also be applied to all electronic still cameras that record and reproduce still images on magnetic disk sheets.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications are possible.

〔Effect of the invention〕

As described in detail above, according to the present invention, by compressing the amplitude of the synchronizing signal portion, the relative amplitude of the video signal portion is increased while maintaining the amplitude of the composite video signal at a predetermined value.
Since M recording is performed and the sync signal portion is expanded during playback, a recording/playback device capable of improving the S/N of the playback image can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a recording/reproducing apparatus according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the embodiment of FIG. 1, and FIG. FIG. 4 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 3, and FIG. 5 is a block diagram showing an example of the structure of a conventional recording/reproducing apparatus. (12) is a pre-emphasis circuit, (13) is a frequency modulator, (17) is a compressor, (18) is a voltage controlled amplifier,
(22) is a demodulator, (23) is a de-emphasis circuit,
(27) is an expander, (29) is a voltage controlled attenuator, (30
) is a control pulse generator.

Claims (1)

[Claims] A composite video signal is supplied to a pre-emphasis circuit, the amplitude of a sync signal portion being output from the pre-emphasis circuit is compressed compared to the video signal portion, and the compressed sync signal portion and the video signal are The signal portion is supplied to a frequency modulator for recording, and at the time of playback, the amplitude of the synchronization signal portion being output from the demodulator is expanded compared to the video signal portion, and the expanded synchronization signal portion and the video signal are 1. A recording/reproducing device characterized in that a signal portion is supplied to a de-emphasis circuit to obtain an original composite video signal.