JPH0636607B2 - Video signal transmission system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal transmission system suitable for use in a magnetic recording / reproducing apparatus for color video signals.

Background Art and its Problems The inventors of the present invention have been able to perform high density recording in a magnetic recording / reproducing apparatus for color video signals as shown in FIGS.
The luminance signal Y in the horizontal period (H) And 1H RY color difference signal (R is red signal) The 1H BY color difference signal (B is a blue signal) The time axis compression was performed, and the data were time-division multiplexed during 1H to perform analog recording on, for example, a disk-shaped magnetic recording medium. In the first drawing, I _DY denotes a luminance signal identification signal, the width of the luminance signal identification signal I _DY of half the width of the horizontal synchronization signal, or I _DC indicates a color difference signal identification signal, the width of the color difference signal discrimination signal I _DC to 1/4 of the width of the horizontal synchronizing signal. Incidentally, Japanese Patent Laid-Open No. 56-134891 simply shows that the color television signal is divided into luminance information and chrominance information and recorded in a time division manner.

As a result of various researches on such high-density recording, it was found that it has the following drawbacks.

That is, the identification signals I _DY and I _{D of} the time division multiplexed time base compression signal
_Since the detection of DC is performed using the DC level as a threshold, the second
As shown in the figure, the deviation D is divided into a video signal section V and an identification signal section S.
S / N by increasing the level of the video signal portion V in order to improve the level of the identification signal portion S becomes correspondingly small, this identification signal I _DY, decreases afford detection of I _DC. Further, in order to surely detect the identification signals I _DY and I _DC , if the level of the identification signal section S is increased, the level of the video signal section V becomes smaller, and the S / N of the video signal deteriorates accordingly. .

Further, the widths of the identification signals I _DY and I _DC are each 1 / th of that of the horizontal synchronization signal.
Since it is as narrow as 2 and 1/4, a low-pass filter is provided in the preceding stage of the separation circuit for the identification signals I _DY and I _DC in order to make S / N as usual, and when the cutoff frequency is lowered, the identification signal I _DY, there is a problem that can not be detected can not be distinguished from the other signal not obtained sufficient levels of I _DC. Further, in order to distinguish the luminance signal Y and the color difference signals (RY signal and BY signal), the widths of the identification signals I _DY and I _DC are changed, but since the widths are relatively narrow, The distinction is uncertain. Therefore, there is a disadvantage that the identification signals I _DY and I _DC cannot be detected well.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to improve the S / N ratio of a video signal and to reliably detect an identification signal.

SUMMARY OF THE INVENTION The present invention is a video signal transmission system in which a video signal is a time division multiplexed time axis compressed signal, and the time division multiplexed time axis compressed signal is frequency modulated and transmitted. The identification signal portion of the multiple time axis compressed signal is such that a single wave signal having a lower frequency than the carrier signal of this frequency modulation is superimposed, and according to the present invention, the S / N of the identification signal is improved. There is an advantage that the identification signal can be surely detected as well as being achieved.

Embodiment First, the basic concept of the video signal transmission system of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 shows a recording system of the magnetic recording / reproducing apparatus, and FIG. 4 shows a reproducing system.

In FIG. 3, (1 _Y ), (1 _RY ) and (1 _BY ) are luminance signals Y, RY color difference signals and color signals constituting color image signals as shown in FIGS. 1A, 1B and 1C, respectively. The Y signal, the RY signal, and the BY signal input terminals to which the BY color difference signals are respectively supplied are shown. The Y signal, the RY signal, and the BY signal input terminals (1 _Y ) and (1 _RY ) And (1 _BY ), the Y signal, the RY signal and the _BY signal are supplied to the time axis compression circuit (2), respectively. In this time base compression circuit (2), the brightness signal Y in one horizontal period H as shown in FIG. 1A is time base compressed to 4 / 6H as shown in FIG. A signal identification signal I _DY is provided, and color difference signals RY and BY for one horizontal period H as shown in FIGS. 1B and 1C.
The signals are time-axis-compressed to 1 / 6H as shown in FIG. 1D, and the color difference signal identification signal _IDC is provided to each of the front edges to identify the luminance signal as shown in FIG. 1D during one horizontal period H. Signal I _DY , time axis compression luminance signal Y, color difference signal identification signal _IDC , time axis compression RY color difference signal, color difference signal identification signal I
_{The DC} and time-axis compressed BY color difference signals are temporally consecutive in this order, and are sequentially repeated. This time base compression circuit
The time-division-multiplexed time-axis compressed signal as shown in FIG. 1D, which is the output signal of (2), is supplied to the frequency modulation circuit (3) for frequency-modulating in the frequency range of 9 MHz to 12 MHz and frequency-modulated, The frequency-modulated time-division multiplexed time base compressed signal of the output signal of the modulation circuit (3) is supplied to one input terminal of the addition circuit (4). Also, (5) shows a switching switch,
One fixed contact (5s) of the switching switch (5) is grounded, and the other fixed contact (5i) is connected to the other fixed contact (5i), for example, as shown in FIG. Single-wave signal f _{I of,} for example, 1000
The movable contact (5a) of this switching switch (5) is connected to the input terminal (6) of the single wave signal f _I to which the KHz sine wave signal is supplied.
Is connected to the other input terminal of the adder circuit (4). In this case, the movable contact (5a) of this switching switch (5) is connected to the time axis compression circuit.
The luminance signal identification signal I _DY and the color difference signal identification signal I _DC obtained in (2) are switched in synchronization with the period. That is, the movable setting (5a) of the switching switch (5) is normally connected to one fixed contact (5s), and the movable contact (5a) is switched to the other only when the identification signals I _DY and I _DC. Connect to the fixed contact (5i) of this, and only at this time adder circuit (4)
Is supplied with a single wave signal f _I of, for example, 1000 KHz. The output signal of the adder circuit (4) is recorded on the magnetic recording medium (8) via the magnetic head (7).

To reproduce the signal thus recorded, a reproducing device as shown in FIG. 4 is used. That is, the frequency-modulated time-division multiplexed time-axis compression signal recorded on the magnetic recording medium (8) is reproduced by the reproducing magnetic head (9), and the output signal of the reproducing magnetic head (9) is, for example, a single signal of 1000 KHz. The single wave signal f _I is supplied to the FM demodulation circuit (11) through the high pass filter (10),
The output signal of the FM demodulation circuit (11) is supplied to the time axis expansion circuit (12) and the identification signal separation circuit (13). The high pass filter (10) may be a trap circuit for removing the single wave signal f _I. Also, the output signal of the reproducing magnetic head (9) is, for example, a single wave signal f _{I of} 1000 KHz.
And supplied to the comparison circuit (15) via a low-pass filter (14) for taking out, in the comparison circuit (15), high level only when the output side there is the single wave signal f _I " An identification signal gate signal of 1 "is obtained, and the identification signal gate signal obtained at the output side of the comparison circuit (15) is supplied to the identification signal separation circuit (13) as a gate signal. The low pass filter (14) may be a band pass filter for taking out only the single wave signal f _I. In the identification signal separation circuit (13), only the luminance signal identification signal I _DY and the color difference signal identification signal I _DC are extracted by the identification signal gate signal, and time division multiplexing is performed at the output side of the identification signal separation circuit (13). The luminance signal identification signal I _DY and the color difference signal identification signal I _DC of the time axis compression signal are obtained, and the luminance signal identification signal I _DY and the color difference signal identification signal I _DC are supplied to the time axis expansion circuit (12), respectively.
In the time axis expansion circuit (12), the discrimination signals I _DY and I _DC are used to correct the time axis of the time division multiplexed time axis compressed signal, and the luminance signals Y, RY color difference signals and B-
This is separated into Y color difference signals. The luminance signal of 1 is expanded to the luminance signal of 1H, and R-Y color difference signal of 1H and R-Y color difference signal of 1H
Y color difference signal and BY color difference signal are expanded to a luminance signal output terminal (12Y), an _RY signal output terminal ( _12RY ) and a _BY signal output terminal ( _12BY ), respectively. And C, the luminance signal Y, the RY signal and the BY signal are obtained.

According to such a video signal transmission system, the time-division multiplexed time-axis compression signal is recorded on the magnetic recording medium (8), so that high density recording of a color video signal is possible.

Also In this video signal transmission system, time division multiplexing identification time warp signal signal I _DY and I _DC unit to a single low frequency e.g. 1000KHz than the carrier signal, for example 9MHz~12MHz of this frequency modulation after frequency modulation Since the wave signal f _I is superimposed, the identification signals I _DY and I _DC are used by using this single wave signal f _I.
Can be detected, and the detection of the identification signals I _DY and I _DC becomes reliable. Therefore, the video signal and the identification signal can use the deviation 100% respectively, and the S / N of the video signal and the identification signal can be improved accordingly, and as a result, the image quality can be comprehensively improved.

Next, an embodiment of the present invention will be described with reference to FIGS. 6, 7, and 8. In the present embodiment, different single wave signals f _Y and f _C are superimposed on the luminance signal identification signal I _DY and the color difference signal identification signal I _DC after the frequency modulation of the time division multiplexed time axis compressed signal. It has become.

This example will be described below. In FIGS. 6 and 7, parts corresponding to those in FIGS. 3 and 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 6 shows a recording system of this example. In FIG. 6, the changeover switch (5) in FIG. 3 is a three changeover switch, and the first fixed contact (5s) is grounded. Second fixed contact (5
Y) is a frequency-modulated carrier signal as shown in FIG.
The third fixed contact is connected to the first single wave signal input terminal (6Y) to which the first single wave signal f _Y having a sine wave of 2000 KHz, which is sufficiently lower than Hz to 12 MHz, is supplied. (5c) is a frequency-modulated carrier signal as shown in FIG.
A second single wave signal input terminal (6c) to which a second single wave signal f _C of a sine wave having a second frequency sufficiently lower than MHz, for example, 1000 KHz is connected, and this switching switch (5) is connected. The movable contact (5a) is connected to the second fixed contact (5Y) for the period of the luminance signal identification signal I _DY obtained in the time base compression circuit (2),
This movable contact (5a) is the third fixed contact during the period of the color difference signal identification signal I _DC obtained in the time base compression circuit (2).
The movable contact (5a) is connected to the first fixed contact (5s) for the other period. Others are the same as those in FIG.

Therefore, in the example of FIG. 6, on the output side of the addition circuit (4), for example, the luminance signal identification signal I _DY of the signal obtained by frequency-modulating the time division multiplex time axis compressed signal as shown in FIG. 2000
First signal single wave signal f _Y is the second single wave signal f _C of the color difference signal discrimination signal I _DC unit while being superimposed example 1000KHz is superimposed KHz is obtained, the signal magnetic It is recorded on the magnetic recording medium (8) via the head (7).

FIG. 7 shows a reproducing system of this example. In FIG. 7, the output signal of the reproducing magnetic head (9) is, for example, 2000 KHz and 10
The first and second single-wave signals of 00 KHz f _Y and f _C are supplied to the FM demodulation circuit (11) through a high-pass filter (10), and the output signal of the FM demodulation circuit (11) is supplied to the time signal. Axis extension circuit
(12) and the identification signal separation circuit (13). Further, the output signal of the reproducing magnetic head (9) is passed through a first low-pass filter (14Y) for extracting a first single wave signal f _Y of 2000 KHz, for example, and a first comparison circuit (15
The second low-pass filter (14C) a second comparator circuit via for extracting the second single wave signal f _C of the output signal, for example 1000KHz of the reproducing magnetic head (9) is supplied to the Y) (15C) to supply the first comparison circuit (15Y)
At this output side, the luminance identification signal gate signal which becomes the high level "1" is obtained only when the first single wave signal f _Y exists, and the output side of the first comparison circuit (15Y) Brightness identification signal Gate signal obtained in the identification signal separation circuit
It is supplied to (13) as a gate signal, and in the second comparison circuit (15C), a second single wave signal f is output to this output side.
This second comparison circuit (15) does not obtain a color difference identification signal gate signal which becomes a high level "1" only when _C is present.
The color difference identification signal gate signal obtained at the output side of C) is supplied to the identification signal separation circuit (13) as a gate signal. Others are the same as those in FIG.

It can be easily understood that the same effects as those of the examples of FIGS. 3 and 4 can be obtained also in this example.

In the above-mentioned embodiment, the color video signal is changed to the luminance signal Y.
And the color difference signals (RY signal and BY signal) are separately recorded. However, various signals such as a luminance signal Y and other color signals or a red signal R, a green signal G and a blue signal B are described. It is needless to say that the present invention can be applied to the case where the FM recording is performed in a time-division manner by dividing the signal into a plurality of signals. Further, although the above-mentioned example is an example in which the present invention is applied to the magnetic recording / reproducing apparatus, it goes without saying that the present invention can be applied to other transmission apparatuses. Further, the present invention is not limited to the above-described embodiment, without departing from the gist of the present invention,
Of course, various other configurations are possible.

According to the present invention, it is possible to use 100% of the deviation of both the video signal and the identification signal for transmitting the time-division multiplexed time base compression signal for high-density transmission of the video signal. N can be improved, and the identification signal can be surely detected. As a result, there is an advantage that the image quality can be comprehensively improved.

[Brief description of drawings]

FIGS. 1, 2, 5, and 8 are diagrams for explaining the present invention, and FIGS. 3 and 4 are for explaining the basic concept of the video signal transmission system of the present invention. FIG. 6 is an explanatory diagram showing a recording system and a reproducing system, and FIGS. 6 and 7 are configuration diagrams showing a recording system and a reproducing system of another embodiment of the present invention. (1 _Y ) is a luminance signal input terminal, (1 _RY ) is an _RY signal input terminal, (1 _BY ) is a _BY signal input terminal, (2) is a time axis compression circuit, and (3) is a frequency modulation circuit. , (4) is an adder circuit, (7)
(9) is a magnetic head, (8) is a magnetic recording medium, (10) is a high-pass filter, (11) is an FM demodulation circuit, (12) is a time axis expansion circuit, (13) is an identification signal separation circuit, (14) is a low-pass filter, and (15) is a comparison circuit.

Claims (1)

[Claims] 1. A time-division multiplexing time, wherein a luminance signal and a color signal are time-division multiplexed, and a first identification signal portion and a second identification signal portion are provided at front ends of the luminance signal and the color signal, respectively. In a video signal transmission system in which a time-division multiplexed time-axis compression signal is used as a frequency-compressed signal and is frequency-modulated and transmitted, in the first identification signal section, a first frequency lower than the frequency-modulated carrier signal is used. A single wave signal having a second frequency lower than the carrier signal of the frequency modulation and different from the first frequency is superimposed on the second identification signal section. Characteristic video signal transmission system.