JPS6113892A - System for transmitting video signal - Google Patents

Abstract

PURPOSE:To improve S/N of a video signal and to detect securely an identifying signal by overlapping a single wave signal having frequency lower than that of a carrier signal subjected to frequency modulation with an identifying signal part of a time division multiplex time base compression signal subjected to frequency modulation. CONSTITUTION:A time division multiplex time base compression signal D, that is, output signal of a time base compression circuit 2, is frequency-modulated by a frequency modulation circuit 3 and supplied to one input terminal of an adder circuit 4. A fixed contact point 5s of a changeover switch 5 is grounded, and simultaneously a single wave signal fI having a frequency sufficiently lower than that of a carrier signal subjected to frequency modulation is supplied to other fixed contact point 5i. Moreover, a movable contact point 5a connected to the other input terminal of the adder circuit 4 is synchronized with a luminance signal identifying signal IDY and a color difference signal discrimination signal IDC, both of which are obtained in the time base compression circuit 2, and connected to the fixed contact point 5i only when there are the IDY and IDC. At the time of reproduction, an identifying signal gate signal for going to a high level ''1'' only when the single wave signal fI exists is supplied as a gate signal to an identifying signal separator circuit 13 through a comparator circuit 15 and low pass filter 14 used for fetching the signal fI.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal transmission system suitable for use in a magnetic recording and reproducing device for color video signals.

BACKGROUND TECHNOLOGY AND PROBLEMS The inventors of the present invention have proposed a method for high-density recording in a magnetic recording/reproducing device for color video signals, as shown in FIGS. 1A, B, and CD.
The luminance signal Y of the horizontal period (H) is set to -1-H, and the R- of IH is set to -1-H.
Y color difference signal (R is red signal) -1-HK, IH B-Y
The time axis of the color difference signal (B is a blue signal) was compressed to -1-H, and these signals were time-division multiplexed between IHs and recorded in analog form on, for example, a disc-shaped magnetic recording medium. In this FIG.
C indicates a color difference signal identification signal, and this color difference signal identification signal I
The width of DC is set to 7, which is the width of the horizontal synchronization signal. Furthermore, Japanese Patent Publication No. 5
Publication No. 6-134891 simply discloses a method in which a color television signal is divided into luminance information and chrominance information and recorded in a time-division manner.

After conducting various studies on such high-density recording, it was found that it has the following drawbacks.

That is, the identification signal IDY# of this time division multiplexed time axis compressed signal
Since IDC detection is performed using the DC level as a threshold,
As shown in No. 2-, the deviation D is the same between the video signal section V and the identification signal section S, and in this case, in order to improve the S/N of the video signal, the level of the video signal section ■ is increased. The level of the identification signal section S becomes correspondingly smaller, and the margin for detecting this identification signal IDYJDC decreases.

Furthermore, if the level of the identification signal section S is set high in order to detect the identification signal IDYIIDC reliably, the level of the video signal section V becomes correspondingly low, and there is a problem that the S/N of the video signal deteriorates accordingly.

Furthermore, since the widths of the identification signals IDY and Ipc are narrower than the horizontal synchronizing signals - and -, respectively, a low-pass filter is provided in the front stage of the separation circuit for the identification signals IDYsIDC in order to obtain a S/N ratio as usual. When the frequency is lowered, the level of the identification signal IDYyIDC cannot be obtained sufficiently, making it impossible to distinguish it from other signals and making it impossible to detect it. Furthermore, a luminance signal Y and a color difference signal (RY signal, B
-Y signal), the widths of the identification signals IDY and IDC are changed, but since these widths are relatively narrow, the distinction is uncertain. Therefore, this identification signal I
D.Y.

There was an inconvenience that IDC could not detect well.

OBJECTS OF THE INVENTION In view of the above, an object of the present invention is to improve the S/N ratio of a video signal and to ensure the detection of an identification signal.

Summary of the Invention The present invention provides a video signal transmission method in which a video signal is a time-division multiplexed time-base compressed signal, and the time-division multiplexed time-base compressed signal is frequency-modulated and transmitted. According to the present invention, a single wave signal having a lower frequency than this frequency modulated carrier wave signal is superimposed on the identification signal part of the time division multiplexed time axis compressed signal.
There is an advantage in that it is possible to improve N and also to be able to reliably detect the identification signal.

Embodiment Hereinafter, an embodiment in which the video signal transmission system of the present invention is applied to a magnetic recording and reproducing apparatus for color video signals will be described with reference to FIGS. 3 and 4. FIG. 3 shows the recording system of this example, and FIG. 4 shows the reproducing system of this example.

In Figure 3, (1y), (IR-y) and (I
B-y) are the luminance signal Y, the R-Y color difference signal, and the B-
Y signal, RY signal and B to which Y color difference signal is supplied respectively
- indicates the Y signal input terminal, and indicates the Y signal, RY signal, and B-Y signal input terminal (ly)t (IR-y) and (IB-y). B-
Y signals are respectively supplied to time axis compression circuit (2)K. In this time axis compression circuit (2), the luminance signal Y of one horizontal period H as shown in FIG. Identification signal IDY
In addition, the color difference signals R-Y signal and B-Y signal of one horizontal period H as shown in FIG. A color difference signal identification signal IDC is provided for each, and the luminance signal identification signal IDY% time axis time axis compressed luminance signal difference 1 color difference signal axis compressed B-Y color difference signal is temporally provided in the order of 1 horizontal period H as shown in the first diagram. Repeat this one after another. The time-division multiplexed time-base compressed signal as shown in the first diagram, which is the output signal of the time-base compression circuit (2), is supplied to a frequency modulation circuit (3) that frequency-modulates it in a frequency range of, for example, 9.7 to 12 MHz. frequency modulated,
A frequency-modulated time-division multiplexed time-base compressed signal of the output signal of the frequency modulation circuit (3) is supplied to one input terminal of the addition circuit (4). Further, (5) indicates a changeover switch, one fixed contact (5S) of this changeover switch (5) is grounded, and the other fixed contact (51) is connected to a frequency modulated carrier wave signal, for example, 9MHz, as shown in FIG. ~1
Frequency sufficiently lower than 2MHz, e.g. 500IG1z
~IMHz single wave signal f.

For example, connect to the input terminal (6) of the single wave signal fI to which a 1000 KHz sine wave signal is supplied, and connect the movable contact (5a) of this changeover switch (5) to the other input terminal of the adder circuit (4). do. In this case, this selector switch (5)
The movable contact (5a) is synchronized with the luminance signal identification signal IDY and the color difference signal identification signal Inc obtained in the time axis compression circuit (2), and is switched only during that period. That is, the movable contact (5a) of this changeover switch (5)
is normally connected to one fixed contact (5S), and only when the identification signals IDY and Ipc are present, this movable contact (5a) is connected to the other fixed contact (51), and only at this time is the adder circuit connected to one fixed contact (5S). (4) for example 1000KHz
A single wave signal fI is supplied. The output signal of this adder circuit (4) is sent to a magnetic recording medium (8) via a magnetic head (7).
Record it as follows.

To reproduce the signals recorded in this manner, a reproducing apparatus as shown in FIG. 4 is used. That is, the frequency-modulated time-division multiplexed time axis compressed signal recorded on the magnetic recording medium (8) is reproduced by the reproducing magnetic head (9), and the reproducing magnetic head (9)
9) to FM via a bypass filter (10) that removes the single wave signal fI of 1000IG (z).
The signal is supplied to the demodulation circuit nt+, and the output signal of the demodulation circuit (111) is supplied to the time axis expansion circuit (121) and also to the identification signal separation circuit α4.

Note that the bypass filter (101) may be a trap circuit that removes this single wave signal fI.Also, the output signal of the reproducing magnetic head (9) is converted into a single wave signal fl of 10'O0)G(z). is supplied to the comparator circuit Q51 through a low-pass filter α for extracting the signal, and in this comparator circuit a9, only when this single wave signal fl exists on the output side) The identification signal gate signal obtained at the output side of the comparator circuit α9 is supplied to the identification signal separation circuit +131 as a gate signal. It should be noted that a low pass filter (I41 extracts only the single wave signal f1) may be used. In this identification signal separation circuit f13, only the luminance signal identification signal IDY and color difference signal identification signal IDC are extracted by this identification signal gate signal, and the time-division multiplexed time axis compressed signal is sent to the output side of this identification signal separation circuit f13. Luminance signal identification signal IDY and color difference signal identification signal IDC
and supplies the luminance signal identification signal IDY and the color difference signal identification signal IDC to a time axis expansion circuit (121).In this time axis expansion circuit (121, this identification signal In
y and IDC to correct the time axis of this time-division multiplexed time axis compressed signal and separate it into a luminance signal Y, an RY color difference signal and a B-Y color difference signal, and this -1-H luminance signal is The 7H 2R-Y color difference signal and the B-Y color difference signal are expanded into the IH RY color difference signal and the B-Y color difference signal, respectively, and the brightness signal output terminal (12
The luminance signals Y, RY signal and B- as shown in FIG. It is designed to obtain a Y signal.

In this example, since the time-division multiplexed time axis compressed signal is recorded on the magnetic recording medium (8), high-density recording of color video signals is possible.

Also, according to this example, a single wave signal fI of a frequency lower than the frequency modulated carrier signal, e.g., 9 MHz to 12 MHz, e.g., 1000 KHz, is superimposed on the identification signal IDY and IDC portion of the time-division multiplexed time-base compressed signal after frequency modulation. Therefore, using this single wave signal f1, the identification signal IDY y
IDC can be detected, and this identification signal ID
Detection of Y y I DC becomes reliable. Therefore, the video signal and the identification signal can each utilize 100% of the deviation, and the S/N of the video signal and the identification signal increases accordingly.
As a result, the overall image quality can be improved.

Further, FIGS. 6, 7, and 8 show other embodiments of the present invention, and in this example, a luminance signal identification signal ID7 section and a color difference signal identification signal I after frequency modulation of a time division multiplexed time axis compressed signal are shown.
Single wave signals fY and fC on each side are superimposed on the DC section.

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

FIG. 6 shows the recording system of this example, and in this FIG. 6, the changeover switch (51 in FIG. As shown in FIG. 8, the fixed contact (5Y) of No. 2 is connected to a frequency modulated carrier wave signal, for example, a first single wave signal f of a sine wave with a first frequency sufficiently lower than 9 MHz to 12 MHz, for example, 2000 KHz.
Connect the third fixed contact (5C) to the first single-wave signal input terminal (6Y) to which Y is supplied, and connect the third fixed contact (5C) to a frequency-modulated carrier signal, for example, 9ME (z~12MHz, which is sufficiently lower than The movable contact (5a) of this selector switch (5) is connected to a second single wave signal input terminal (6C) to which a second single wave signal fc of a sine wave of a second frequency, for example, 1000 KHz is supplied. is connected to this second fixed contact (5Y) during the period of the luminance signal identification signal IDY obtained in the time axis compression circuit (2), and this movable contact (5a) is connected to this time axis compression circuit (2). Color difference signal identification signal ID obtained by
The third fixed contact (5c) is connected during the period C, and the movable contact (5a) is connected to the first fixed contact (5S) during the other period.
Connect to. The rest of the structure is the same as that shown in FIG.

Therefore, in the example shown in FIG. 6, on the output side of the adder circuit (4), the luminance signal identification signal IDY part of the frequency modulated time-division multiplexed time axis compressed signal as shown in FIG. 1 single wave signal fy is superimposed on this color difference signal identification signal IDC section, for example, 1000K.
A signal on which the second single wave signal fc of Hz is superimposed is obtained, and this signal is sent to the magnetic recording medium (via the magnetic head (71).
8).

FIG. 7 shows the reproduction system of this example, and in this FIG. 7, the output signal of the reproduction magnetic head (9) is, for example,
Hz and 1000 KHz first and second single wave signals f
A bypass filter for removing Y and fc is supplied to the FM demodulation circuit QIIK via Iα, and the output signal of this FM demodulation circuit αυ is supplied to the time axis expansion circuit α and also to the identification signal separation circuit (131). In addition, the output signal of the reproducing magnetic head (9) is passed through a first comparator circuit (15Y) through a first low-pass filter (14Y) for extracting the first single wave signal fY of 2000IG (z).
K and the output signal of the reproducing magnetic head (9) is passed through a second low-pass filter (14C) for extracting a second single wave signal fc of, for example, 1000 KHz to a second comparator circuit (15C). and in this first comparator circuit (15Y), a luminance identification signal gate signal which becomes high level "1" only when the first single wave signal fY is present on this output side is obtained. None, the luminance identification signal gate signal obtained at the output side of this first comparison circuit (15Y) is supplied as a gate signal to the identification signal separation circuit (13), and this second comparison circuit (15C) The color difference discrimination signal obtained at the output side of this second comparator circuit (15C) is such that a color difference discrimination signal gate signal which becomes high level "1" is obtained only when the second single wave signal fc is present on the output side. Signal gate signal identification signal separation circuit (131
as a gate signal. The rest of the structure is the same as that shown in FIG.

It is easy to understand that the same effects as in the examples shown in FIGS. 3 and 4 can be obtained in this example as well.

In the above embodiment, the case where the color video signal is recorded separately into the luminance signal Y and the color difference signals (RY signal and B-Y signal) has been described, but the luminance signal Y and the other color signals are recorded separately. Of course, the present invention can also be applied to the case where the signal is divided into a plurality of various signals, such as a red signal R, a green signal G, and a blue signal B, and is time-divisionally FM recorded. Further, although the above-mentioned example is an example in which the present invention is applied to a magnetic recording/reproducing device, it goes without saying that the present invention can be applied to other transmission devices. Furthermore, the present invention is not limited to the above-mentioned embodiments, and without departing from the gist of the present invention,
Of course, various other configurations are possible.

Effects of the Invention According to the present invention, it is possible to utilize 100% of the deviation of both the video signal and the identification signal in transmitting time-division multiplexed time-base compressed signals for high-density transmission of video signals. In addition to being able to improve N, the identification signal can be detected reliably, and as a result, there is an advantage that the overall image quality can be improved.

[Brief explanation of drawings]

FIGS. 1, 2, 5 and 8 show the functions of the present invention, respectively.
3 and 4 are block diagrams showing a recording system and a reproduction system of an embodiment of the video signal transmission system of the present invention, and FIGS. 6 and 7 are diagrams showing a further embodiment of the present invention. FIG. 2 is a configuration diagram showing a recording system and a reproducing system. (IY) is a luminance signal input terminal, (IR-Y) is an RY signal input terminal, (IB-y) is a B-Y signal input terminal, (2
) is a time axis compression circuit, (3) is a frequency modulation circuit, (4)
is an adder circuit, (7) and (9) are respectively magnetic heads, (8
) is a magnetic recording medium, flol is a bypass filter, (
Ill is an FM demodulation circuit, 121 is a time axis expansion circuit, (1
31 is an identification signal separation circuit, I is a low-pass filter, (
151 is a comparison circuit. Figure 2 Figure 5 Figure 8 cfY Figure 6 Figure 7

Claims (1)

[Claims] In a video signal transmission method in which a video signal is a time-division multiplexed time-base compressed signal, and the time-division multiplexed time-base compressed signal is frequency-modulated and transmitted, the frequency-modulated time-division multiplexed time-base compressed signal is A video signal transmission system characterized in that a single wave signal having a lower frequency than the frequency modulated carrier wave signal is superimposed on the identification signal section.