JPS6267994A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To reduce, what is called, the color bleeding of a reproducing color picture by controlling the quantity of a feedback in accordance with an operating mode in a device in which a comb-line filter is constituted as a feedback type. CONSTITUTION:The connection switch 14 of the comb-line filter 8 is turned on during an ordinary reproducing mode. Therefore, when an inputted signal has the level of small amplitude, as shown by a full line (a) in Fig. A, a comb- line characteristic having summits at frequencies integer times of a horizontal frequency fh is obtained, and as the inputted signal has the level of larger amplitude, as shown by broken lines (b) in the same figure, a flat characteristic is more obtained. Accordingly, in this comb-line filter 8, the noise component of a small amplitude level is removed. Namely, a luminance signal in which the output of a subtracter 8e, that is, the nose component is removed as the output of the comb-line filter 8 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal reproducing device in which a feedback comb filter is inserted in a color signal reproducing system.

[Summary of the invention]

The present invention provides a video signal reproducing device in which a comb filter for 87M improvement is disposed in a color signal reproducing system, and the comb filter is configured as a feedback type, and the amount of feedback is adjusted according to the operation mode. This control reduces so-called color fringing in reproduced color images.

[Conventional technology]

Conventionally, it has been known to provide a 571J improvement comb filter for removing crosstalk from adjacent tracks and other noises in the color signal reproduction system of a video tape recorder (VTR). In order to achieve even greater improvements, the use of a feedback type is being considered.

FIG. 5 shows an example.

In the figure, a carrier color signal C reproduced in a VTR is supplied to a terminal (2111).
includes crosstalk components from adjacent tracks in a frequency interleaved relationship.

This carrier color signal C is supplied to a subtracter (a) constituting a comb filter (1). The carrier color signal C9 from this subtractor (A) is directly supplied to the subtractor (A), and
The signal is supplied to a subtracter via a delay line (C) having a delay time of H (H is a horizontal period). Then, in this subtractor, the carrier color signal C1D delayed by IH in the delay line (C) is subtracted from the carrier color signal C4, and the terminal (C) derived from this subtractor (E) is outputted from the carrier color signal C4. A carrier color signal C2 from which noise has been removed is output.

Further, the carrier color signal C1 from the subtracter (c) is sent to the adder (c).
It is supplied directly to the adder (c) via the delay line (c). The addition signal from the adder (c) is supplied to fixed terminals on the A side and B side of the changeover switch via variable attenuators (a) and (c), respectively. Attenuation jk1 of this variable attenuator (goods) and (c). and t2 is, for example, 12>1. It is said that

The signal obtained from the changeover switch is supplied to a subtracter (A) as a feedback signal S, and in this subtracter (A), the feedback signal S is subtracted from the carrier color signal C, and the carrier color signal C1 is extracted. It will be done.

Further, (to) is a correlation detection circuit that detects the vertical correlation of the luminance signal related to the carrier color signal. Terminal 0]) has V
A luminance signal Y reproduced in TR is supplied. This luminance signal Y is directly supplied to the subtracter 09, and the IH
A subtractor through a delay line (t) with a delay time of ? 39
supplied to Then, in this subtracter 02, the luminance signal YD is delayed by IH from the luminance signal Y by the delay line (to).
is deducted. Output S taken out from this subtractor G
□ is supplied to the detector (to) via the low-pass filter 04. This detector (a) outputs a switching control signal S8W depending on whether the level of the absolute value of the output SY is greater than or equal to a predetermined value.
is supplied to the changeover switch (A).

When the level of the absolute value of the signal SY is less than a predetermined value, it is determined that there is a correlation with the carrier color signal, and the changeover switch () is switched to the A side to increase the amount of feedback. Therefore, the comb-shaped filter rod has a C-shaped comb-shaped filter characteristic as indicated by the broken line a in FIG.

When there is vertical correlation, the carrier color signal has a frequency (n+')f
h (where n is a natural number and /h is a horizontal frequency), the intensity is strongly concentrated near the area, so that the distortion is greatly improved.

On the other hand, when the level of the absolute value of the signal SY exceeds a predetermined value, it is determined that there is no correlation between the carrier color signals, and the selector switch is switched to the B side, so that the amount of feedback is reduced. Therefore, the comb-shaped filter rod has a C-shaped comb-shaped filter characteristic as shown by the dashed-dotted line in FIG. Incidentally, the solid line C in the figure shows the characteristic when the amount of feedback is zero.

The comb-shaped filter shown in the example shown in FIG. 5 is described in detail in, for example, Japanese Patent Laid-Open No. 160288/1983.

[Problem that the invention seeks to solve]

According to the example shown in FIG. 5, the correlation between carrier color signals is determined based on the correlation between luminance signals. this is,
This is because it is extremely difficult to make a judgment based on the carrier color signal due to adjacent crosstalk. Here, there is no problem if the correlation of the luminance signal and the correlation of the carrier color signal match, but they do not necessarily match. For example, if the carrier chrominance signal has no correlation, the main luminance signal may have a correlation. In this case, according to the example in Figure 5, it is determined that there is a correlation, so
Since the changeover switch 4 is switched to the A side and the amount of feedback in the feedback path is increased, large color blurring occurs in the vertical direction of the reproduced color image. According to a VTR having such a playback system, there is not much of a problem with one recording/playback, but if so-called dubbing is repeated twice, three times, etc.
Color bleeding gradually becomes noticeable and becomes a problem.

In view of this point, the present invention is designed to reduce color blur in reproduced color images as described above.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention is designed to control the amount of feedback of the comb-shaped filter according to the operation mode. For example, the amount of feedback is made smaller in dubbing mode than in normal playback mode.

[Effect]

For example, in the dubbing mode, the feedback amount is smaller than in the normal reproduction mode, so even if it is determined that there is no correlation in the carrier color signals, or even if it is determined that there is a correlation, the vertical color of the reproduced color image Bleeding is significantly reduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the figure, (1) is a reproducing magnetic head, and signals (FM modulated luminance signal Y7 and low-frequency carrier color signal C) reproduced from a magnetic tape (not shown) by this magnetic head (1).
The synthesized signal with L) is supplied to a high-noise filter (3) via a reproduction amplifier (2), and a modulated luminance signal YFM is obtained from this high-noise filter (3).

This modulated luminance signal YWM is passed through a limiter (4) to FM
The signal Y is supplied to a demodulator (5), and a luminance signal Y is obtained from the demodulator (5). This luminance signal Y is passed through a de-emphasis circuit (6) to an np that constitutes a peaking circuit (7).
Supplied to the base of an n-type transistor Q. in this case,
The frequency characteristic for the medium amplitude level at the output end of the de-emphasis circuit (6) is a characteristic with a low response in the medium range, as shown by the solid line a in FIG. For this reason, the peaking circuit (7) is for emphasizing the midrange and improving sharpness.

The emitter of the transistor Q of the peaking circuit (7) is
The changeover switch (1
Connected to the N-side fixed terminal of 1. Also.

The emitter of the transistor Q is connected to a fixed terminal on the D side of the changeover switch (to) through a series circuit of a coil LD, a capacitor CD, and a resistor RD, which constitute a series resonant circuit (7D). The movable terminal of this changeover switch αj is grounded.

The changeover switch (to) is connected to the fixed terminal on the N side in the normal reproduction mode, and to the D side in the dubbing mode.

The frequency characteristic for the medium amplitude level at the output end of the peaking circuit (7) is made to be a characteristic in which the mid-range is emphasized in the normal reproduction mode, as shown by the dashed line in FIG. At the same time, in the dubbing mode, the amount of emphasis is reduced, as shown by the broken line C in the figure.

The luminance signal Y obtained from the peaking circuit (7) is supplied to a comb filter (8) that removes noise in the vertical direction. This comb filter (8) utilizes the fact that there is a strong line correlation between the reproduced luminance signal and its IH (one horizontal period) delayed signal, and as the difference output between the two, a noise component due to the line correlation is obtained. It is. That is, the luminance signal Y is supplied as is to the subtracter (8a), and the luminance signal Y1 is supplied via the delay line (8b) having a delay time of IH (one horizontal period). And the subtractor (
The output of 8a) is supplied to a subtracter (8.) via a limiter (8c), a resistor (8d) and a connection switch 04.
A luminance signal Y is supplied to this subtracter (8e). The connection switch Q4 is turned on in the normal reproduction mode and turned off in the dubbing mode.

Also, the luminance signal Y2 obtained from the comb filter (8)
is a noise canceller that removes horizontal noise (
9). This noise canceler (9) is
High-frequency components with small amplitude levels are determined to be noise components, and the noise is removed. That is, the luminance signal Y2 is supplied to a high male filter (9a) and its high frequency components are extracted. This high frequency component is supplied to a limiter (9b), a small amplitude level component is extracted, and supplied to a subtracter (9d) via a resistor (9c) and a connection switch (to).

The subtracter (9d) is supplied with the luminance signal Y2. The connection switch (g) is turned on in normal reproduction mode and turned off in dubbing mode.

The luminance signal Y3 obtained from the noise canceller (9) is supplied to the synthesis circuit α1.

Further, the output of Anne7° (2) is supplied to a low-pass filter α°C, and a low-pass carrier color signal CL is obtained from this low-pass filter α°C. This carrier color signal CL is supplied to a frequency conversion circuit (A), and the carrier color signal C from this frequency conversion circuit 09 is supplied to a terminal (C) of a comb-shaped filter via a band i4 filter 0Q. The carrier color signal C2 obtained at the output terminal (c) of this comb-shaped filter is supplied to a synthesis circuit α1, and a color video signal S is output from this synthesis circuit α0. V is obtained.

Further, in the comb-shaped filter screen, a connection switch Oi is inserted between the feedback path, for example, the changeover switch (A) and the subtractor (A). This connection switch is turned on in the normal reproduction mode and turned off in the dubbing mode.

In addition, the peaking circuit (7) changeover switch 0], the comb filter (8) connection switch 04, the noise canceller (9) connection switch (c), the comb filter (7)
The connection switch positions are controlled in conjunction with each other.

This example is configured as described above.

In this example, the peaking circuit (7) changeover switch (
) is connected to the N side in normal playback mode and to the D side in dubbing mode, so the peaking circuit (7
), the frequency response for the medium amplitude level at the output end is, in the normal playback mode, an emphasized midrange characteristic as shown by the dashed line in Figure 2, and in the dubbing mode, as shown by the dashed line in the same figure. As shown in C, the amount of emphasis is reduced.

In addition, the connection switch (14) of the comb-shaped filter (8) is
It is turned on in normal playback mode. Therefore,
When the input signal has a small amplitude level, it has a comb-shaped characteristic that peaks at frequencies that are integral multiples of the horizontal frequency fh, as shown by the solid line 1 in Figure 4.On the other hand, when the input signal has a large amplitude level, it has a comb-shaped characteristic. Indeed, as shown by the broken line in the same figure, the characteristic approaches the 7-rat characteristic. Therefore, in this comb filter (8), noise components that are generally at a small amplitude level are removed.

That is, the output of the subtracter (8e), that is, the comb filter (
8), the noise component is removed and a psychic luminance signal is obtained. In addition, the connection switch α of the comb filter (8)
The rod is turned off when in dubbing mode. Therefore, the characteristics of the comb filter (8) are flat, as shown by the broken line in FIG. 3, regardless of the amplitude level of the input signal.

In addition, the connection switch (Is) of the noise canceller (9)
is turned on in normal playback mode.

Therefore, when the input signal has a small amplitude level, the characteristics of this noise canceller (9) are as shown in the solid line 1 in Figure 4.
As shown in the figure, the response in the high range is reduced,
On the other hand, the larger the amplitude level of the input signal is, the closer it becomes to flat characteristics as shown by the broken line in the figure. Therefore, in this noise canceller (9), high frequency noise components are removed. That is, the output of the subtractor (9d),
In other words, a luminance signal from which high-frequency noise components have been removed is obtained as the output of the noise canceller (9). Incidentally, although the noise canceller (9) can remove vertical striped noise that cannot be removed by the comb filter (8), it is unable to remove noise components in the middle and low ranges. In other words, the comb filter (8) and the noise canceller (9) work together to effectively remove noise.

In addition, the connection switch (T) of the noise canceller (9)
is turned off when in dubbing mode.

Therefore, the characteristics of the noise canceller (9) are flat, as shown by the broken line in FIG. 4, regardless of the amplitude level of the input signal.

Further, in this example, the connection switch (3) of the comb-shaped filter screen is turned on in the normal reproduction mode. Therefore, a return path is always formed, and SA is improved. On the other hand, the connection switch (2) of the comb filter (1) is turned off in the dubbing mode. Therefore, the return route is cut off.

Thus, according to this example, when the dubbing mode is used, the peaking circuit (
The frequency characteristic for the medium amplitude level at the output end of 7) is a characteristic with a reduced amount of emphasis. Therefore, even if dubbing is repeated twice, three times, etc., it is possible to avoid that only the middle range of the luminance signal is extremely emphasized.

Please note that when the dubbing mode is selected, the characteristics of the comb filter (8) and noise canceller (9) are flat regardless of the amplitude level of the input signal. Therefore, even if dubbing is repeated twice, three times, etc., it is possible to avoid the gradual loss of small amplitude level components of the luminance signal.

Further, according to this example, when the dubbing mode is set,
Since the return path of the comb-shaped filter in the color signal reproduction system is cut off, the color in the vertical direction of the reproduced color image is Bleeding can be significantly reduced.

In the above-mentioned embodiment, a connection switch is inserted in the return path of the comb-shaped filter to completely cut off the return path during dubbing mode.
A variable attenuator may be provided in place of the connection switch (g) to reduce the amount of feedback during dubbing mode.

Further, in the above embodiment, the comb filter (8) is provided with the connection switch 04, and when in the dubbing mode,
The connection switch α→ is turned off, and the limiter (8
Although the output of c) is not supplied to the subtracter (8e) at all, the amount supplied to the subtracter (8θ) may be reduced. This also applies to the noise canceller (9).

Further, in the above embodiment, the feedback amount of the comb filter (1) is controlled depending on the normal reproduction mode or the dubbing mode, but apart from this, multiple modes in which the magnetic tape runs at different speeds are controlled. It is also conceivable to configure the system so that the faster the running speed is, the smaller the amount of feedback is. That is, the faster the mode is, the better the SA becomes, so the meaning of configuring it as a feedback type diminishes. By reducing the amount of feedback in this way,
Color fringing is reduced as in the above embodiment.

Similarly, in a device having a plurality of modes in which different types of magnetic tapes are used, it may be possible to configure the system so that the amount of feedback decreases as the mode uses a magnetic tape with a better S/N ratio of the conveyed color signal.

〔Effect of the invention〕

According to the present invention described above, since the feedback amount of the feedback comb filter inserted in the color signal reproduction system is controlled according to the operation mode, color fringing in reproduced images can be significantly reduced. be able to.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing one embodiment of the present invention, Figures 2 to 4
The figure is a characteristic diagram for explaining the same, FIG. 5 is a configuration diagram of an example of a feedback comb filter, and FIG. 6 is a characteristic diagram for explaining the same.线 is a comb-shaped filter, (g) is a correlation detection circuit, and 01 is a connection switch. 1N Kaisho G2 7994 (6) Circumferential wrinkle number H leak 7°'no,'l aF314 th t=I
+nSpecial')q Figure 2 Shufu number Kuushi! Filter Sentence January 6 Talents for 'Sumizu Figure 3 Figure 5/Iss'Kiif ra ω for explanation r characteristic diagram Figure 4 Kum type sultan n special l to student group for the blind teacher Figure 6

Claims (1)

[Claims] 1. In a video signal reproducing device in which a comb filter for S/N improvement is disposed in a color signal reproducing system and the comb filter is configured as a feedback type, A video signal reproducing device characterized in that the amount of feedback of the comb filter is controlled. 2. The video signal reproduction according to claim 1, wherein the operation mode includes a normal playback mode and a dubbing mode, and the feedback amount is smaller in the dubbing mode than in the normal playback mode. Device. 3. The video image according to claim 1, wherein the operation mode includes a plurality of modes in which the magnetic tape runs at different speeds, and the faster the speed of the magnetic tape runs, the smaller the feedback amount becomes. Signal regenerator. 4. The operation mode has a plurality of modes in which different types of magnetic tapes are used, and the feedback amount is reduced as the mode uses a magnetic tape with a higher S/N ratio of the color signal. A video signal reproducing device according to claim 1.