JPH0417485A - Video signal processing unit - Google Patents

Abstract

PURPOSE:To decease the deterioration in a luminance signal and to improve dot disturbance and flicker of a chroma signal by detecting a saturation level of the chroma signal and eliminating the residence chroma signal component included in the luminance signal in response to the level. CONSTITUTION:A saturation detection circuit 38 of this unit detects whether or not a saturation level of a chroma signal is higher than a prescribed level with respect to a chroma signal whose burst level is constant by an ACC circuit 6 so as to activate a notch circuit 37 only when the saturation is high in which the effect of dot disturbance is strongly caused. The notch circuit 37 consists of a resistor, a capacitor, a coil and a transistor(TR) in combination to eliminate selectively the chroma signal resident in a Y/C separation circuit 2 from the luminance signal. The chroma signal component is selectively eliminated from the luminance signal by the notch circuit in response to the saturation level of the chroma signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device for a video tape recorder (VTR), a television, etc., and particularly to a video signal processing device for improving dot interference and the like.

[Conventional technology]

FIG. 7 is a block diagram of a recording section in a conventional VTR, and FIG. 8 is a block diagram of a reproducing section in a conventional VTR.

In the recording section shown in FIG. 7, in the conventional video signal processing device, a video signal (1) is input to a Y/C separation circuit (2), where it is separated into a luminance signal and a chroma signal.

The separated luminance signal passes through a low-pass filter (3) and an emphasis (4), corrects its frequency characteristics, and then is modulated by an FM modulation section (5) to become an FM signal.

In addition, the separated chroma signal has a constant burst level in ACC (6), and burst emphasis (
In step 7), the burst level is raised by 6 dB, and the frequency of 3°58 MH±500 kHz is frequency-converted into a chroma signal of 629 kHz±500 kHz by the low frequency conversion circuit (8).

Then, this chroma signal and the FM signal of the luminance are combined in a mix circuit (9), and the signal is recorded on a magnetic tape (12) by a recording amplifier (10) and a head (11).

The above Y/C separation circuit (2) is illustrated in FIG. 9(A), for example.
It consists of a circuit as shown in . In the NTSC signal, so-called comb separation is performed in which the chroma signal is separated into a luminance signal and a chroma signal by utilizing the fact that the phase of the chroma signal is inverted every horizontal scan (hereinafter also referred to as IH).

For example, in FIGS. 9(B) and (C), the nth line chroma signal (13) and the n+1th line chroma signal (14)
It can be seen that the phase is reversed. Therefore, as shown in FIG. 9(A), the video signal (1) passed through the delay circuit (IHdelay) (15) for one horizontal scanning period and the video signal passed through the buffer (16) are added together. By adding the chroma signals in the unit (18), the chroma signals have opposite phases and are removed, so that a luminance signal is obtained.

On the other hand, since the luminance signal subjected to IH delay (15) has a correlation with the original video signal, by subtracting it in the subtracter (20), the luminance signal is removed and a chroma signal is obtained.

However, from the n+1st line (14) to n in the same figure (D)
As shown in the +2nd line (17), if the chroma signal suddenly disappears, an unnecessary chroma component (19) may be generated in the luminance signal output from the adder (18). This is the cause of dot interference.

Next, the playback section of the VTR will be explained with reference to FIG.

A video signal recorded on a magnetic tape (12) is picked up by a head (11), and the picked up video signal is branched through a head amplifier (21) and subjected to luminance signal processing and chroma signal processing.

Luminance signal processing is performed by setting the reproduction output to a constant level in the FMAGC (22), demodulating it to a luminance video signal in the FM demodulation section (23), and then applying a de-emphasis (24), a low-pass filter (25), and a noise canceller (26). A reproduced luminance signal is obtained through the

In addition, in the chroma signal processing, the low-frequency chroma signal (629kHz±500kHz) is processed by the low-pass filter (27).
Only the component is allowed to pass through, and the level is adjusted to a constant burst level at ACC (28). and,
The <-strike that was raised during recording was lowered by 6 dB using the Burst Day Enfussis (29) to return to the original level, and the frequency conversion circuit (30) was used to convert the frequency to 3.58 MHz ± 500 kHz.
The video output (32
) is obtained.

Furthermore, FIG. 10 is a block diagram of a Y/C separation circuit in a conventional television. The video signal (1) in Fig. 10 is
The Y/C separation circuit (2) separates the luminance signal, and the luminance signal passes through a notch circuit (33) and is processed as a luminance signal output (34).

On the other hand, the separated chroma signal passes through an ACC circuit (6) and is processed as a chroma signal output (35). However, in this case as well, there is the problem of dot interference as described above, so here the notch circuit (33) can be controlled by operating the user control switch (36).

[Problem to be solved by the invention]

As mentioned above, in conventional video signal processing devices, in the Y/C separation circuit that separates the video signal into a luminance signal and a chroma signal, if the chroma signal suddenly disappears due to a color change, the accurate video signal cannot be accurately detected. There is a problem in that separation cannot be performed and the chroma signal remains in the luminance signal, causing dot interference.

Further, when recording a video signal, if the residual chroma signal is present when recording a luminance signal, it is recorded as a luminance signal, so there is a problem that dot interference also occurs during playback.

Furthermore, when the chroma signal remaining in the luminance signal during the reproduction and the reproduced chroma signal are combined, there is a problem that the chroma signals interfere with each other and flicker occurs.

The present invention was made with the aim of solving the above-mentioned problems, and the purpose is that when separating video signals by Y/C separation, the chroma signal suddenly disappears and the luminance signal is mixed in. An object of the present invention is to provide a video signal processing device that can reduce dot interference and flicker by selectively removing chroma signals even if they remain.

[Means to solve the problem]

In order to solve the above problems, a video signal processing device according to the present invention includes a saturation detection circuit that detects a saturation level of a chroma signal, and a saturation detection circuit that detects a saturation level of a chroma signal. and a notch circuit for removing residual chroma signal components included in the luminance signal, and selectively removing unnecessary chroma signal components included in the luminance signal.

[Effect]

According to the video signal processing device having the above configuration, the saturation level of the chroma signal is detected, and, for example, the 3.58M signal for the luminance signal is limited to the highly saturated portion where dot interference is large.
By selectively removing the Hz chroma signal component,
This is to improve dot interference and chroma flicker while minimizing deterioration of the luminance signal.

〔Example〕

Hereinafter, preferred embodiments of a video signal processing apparatus to which the present invention is applied will be described with reference to the drawings.

First Embodiment FIG. 1 is a block diagram showing one embodiment of the present invention, and each figure in FIG. 2 is an explanatory diagram of a notch circuit, in which (A) is a characteristic waveform diagram of the notch circuit, and (B) is Circuit diagram of Notchi circuit, Part 3
The figure is a circuit diagram of the chroma saturation detection circuit, Figures 4 (A) to (
G) is a waveform diagram illustrating chroma signal and saturation detection.

Note that the symbols (1) to (12) in FIG. 1 are the same as those in FIG. 7 of the conventional example, so the explanation will be omitted.

As shown in FIG. 1, the characteristic configuration of this embodiment includes a saturation detection circuit (38) that detects the saturation level of the chroma signal, and a saturation detection circuit (38) that can selectively remove a predetermined signal component from the luminance signal. It has a notch circuit (37).

First, in the recording section of the VTR shown in Figure 1, when a video signal (1) is input from the video signal input section and separated into a luminance signal and a chroma signal by the Y/C separation circuit (2), the color As mentioned above, when the chroma signal is temporarily lost at the change of the brightness signal, the chroma signal remains in the luminance signal.

Therefore, as it is, the luminance signal including the chroma signal will become FM.
The residual chroma signal is modulated by a modulator (5) and processed as a luminance signal. Therefore, dot interference occurs during reproduction.

Therefore, in the video signal processing apparatus of this embodiment, as shown in FIG. 1, a notch circuit (37) is provided after the low-pass filter (3). The characteristics of the notch circuit (37), as shown in FIG. 2(A), are such that it reduces the output at 3.58 MHz and removes only the chroma signal component in the luminance signal. As shown in FIG. 2(B), this notch circuit has a resistance (
71), a capacitor (72), a coil (73), and a transistor (74).

By inserting a notch circuit (also called a trap circuit) (37) having the above characteristics, the chroma signal remaining in the Y/C separation circuit (2) can be selectively removed from the luminance signal.

On the other hand, the saturation level of the chroma signal can be detected by inserting a saturation detection circuit (38) into the chroma signal whose burst level has been made constant by the ACC circuit (6) in Figure 1. This is to detect when the value becomes higher than a predetermined level.

The two are connected so that the notch circuit (37) operates only when the degree of saturation is high and the influence of dot interference is strong.

If the notch circuit (37) is constantly operated regardless of the saturation level of the chroma signal, the 3,58
This is because the MHz component is completely eliminated, which affects the luminance signal.

Next, Fig. 3 shows a chroma signal saturation detection circuit (38).
- An example is illustrative. As shown in the figure, when a chroma signal is input from the left, first, a capacitor (39) performs DC cut. The transistor (42) is connected to the resistor (
Bias is applied from 40) and (41), and the amplified output from the collector of the transistor (42) is applied to the base of the transistor (50). Here, the bias of the transistor (50) is set to approximately 066V, so the upper half of the chroma signal of O■ or more is output to the emitter, as shown in the waveform (64) in FIG. 4(B).
Capacitor (52), Resistor (53), Capacitor (55
), is integrated by the resistor (54) and doubled by the amplifier (56), and the chroma signal is converted into a direct current in one vertical scanning period, as shown in the waveform (66) of FIG. 4(C).

This output is then input to the comparator (61) shown in FIG. Here, the level indicated by Vr (65) in FIG. 4(C) is created by the resistors (59) and (60) in FIG. Therefore, FIG. 4(C) l:show tv r (
The waveform shown in FIG. 6(D) above the level of 65) can be detected. This detected saturation level equal to or higher than the predetermined level is input to the base of the transistor (74) of the notch circuit shown in FIG. 2(B). Here, the capacitor (72) and the coil (73) are grounded to form a series resonant circuit, and the characteristics shown in FIG. 2(A) can be produced.

In addition, in the chroma signal saturation detection circuit 38 in this embodiment, the detection circuit for one vertical period is shown, but if the chroma signal is detected by balanced detection of the chroma signal waveform (67) shown in FIG. 4(E), , the waveform (68) in the same figure (F)
The saturation level of the chroma signal during one horizontal scanning period can be detected as shown in FIG. 4(G), and the notch circuit (37) can also be controlled during one horizontal scanning period.

Second example FIG. 5 is a block diagram showing another embodiment of the present invention.

This embodiment is a video signal processing device that uses the video signal of a television receiver after Y/C separation by comb separation.

As in the first embodiment, when the chroma signal changes, the comb separation malfunctions and the chroma signal remains in the luminance signal, causing dot interference. For this reason,
The saturation detection circuit (38) in the figure detects only the highly saturated portion of the chroma signal (portion with large dot interference) and operates the notch circuit to remove unnecessary components at 3.58 MHz from the luminance signal. Can be removed. This makes it possible to reduce the deterioration of image quality and improve dot interference.

Third embodiment FIG. 6 is a block diagram showing another embodiment of the present invention.

In the figure, symbols (21) to (32) are the same as those in the conventional example shown in FIG. 8, so repeated explanation will be omitted.

This embodiment is a video signal processing device for a case where a chroma signal remains in a luminance signal during recording of a video signal of a VTR.

If a luminance signal in which this chroma signal remains is recorded, when it is reproduced, dot interference will occur as in the case described above.

Therefore, the video signal is reproduced by the head (11), and the chroma signal remains in the luminance signal that has passed through the noise canceller (26). Therefore, it passes through the No-Sochi circuit (37). This notch circuit (37) is a frequency conversion circuit (30).
) is detected and controlled by a saturation detection circuit (38).

This selectively removes only the residual chroma signal which was included in the luminance signal during recording and which causes a large amount of dot interference, thereby making it possible to improve dot interference during reproduction.

Furthermore, the slight chroma component that remains in the luminance signal due to comb separation during recording (different from the residual chroma signal in the changing part of the chroma signal mentioned above) is particularly large in the highly saturated part of the chroma signal. . Another problem is that flicker occurs due to interference of the chroma signal when this chroma component is mixed with the chroma signal in the mixer circuit (31). However, flicker can be improved by removing the chroma signal remaining in the luminance signal using the notch circuit (37) and saturation detection circuit (38).

As described above, the video signal processing device of this embodiment is
By detecting the saturation level of the chroma signal and operating the notch circuit when the saturation level is above a predetermined level, it selectively removes the 3.58 MHz chroma signal remaining in the luminance signal, thereby eliminating dot interference and It is possible to improve flicker.

〔Effect of the invention〕

As described above, according to the present invention, in order to prevent dot interference and chroma flicker caused by the residual chroma signal included in the luminance signal, the saturation level of the chroma signal is detected and the signal is adjusted according to the saturation level. Since the chroma signal component is selectively removed from the luminance signal by the notch circuit, deterioration of the luminance signal can be reduced and dot interference and flicker can be appropriately improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of a notch circuit, in which (A) is a characteristic waveform diagram of the notch circuit, (B) is a circuit diagram of the notch circuit, Figure 3 is a circuit diagram of a chroma saturation detection circuit, Figures 4 (A) to (G) are waveform diagrams explaining chroma signals and saturation detection, and Figure 5 is a block diagram showing another embodiment of the present invention. 6 is a block diagram showing another embodiment of the present invention, FIG. 7 is a block diagram of a recording section in a conventional VTR, FIG. 8 is a block diagram of a reproducing section in a conventional VTR, and FIG. A) to (E) are Y/
FIG. 10, which is a diagram for explaining the C separation circuit, is a block diagram of the Y/C separation circuit in a conventional television. In the figure, (1) is a video signal, (2) is a Y/C separation circuit, (3) is a low-pass filter, (4) is an emphasis, (5) is an FM modulator, (6) is an ACC circuit, and (7) is a video signal. )
is burst emphasis, (8) is frequency low range conversion circuit, (9) is mix circuit, (10) is recording amplifier, (1
1) is a head, (12) is a magnetic tape, (37) is a notch circuit, and (38) is a saturation detection circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Patent attorney Yoshi 1) Kenji (2 others) (A) Characteristic waveform diagram of Notchi circuit Explanatory diagram of Nonchi circuit Figure 2 Y/C separation circuit Y/C separation circuit Diagram to explain: Block diagram of Y/C separation circuit in conventional television No. 1
Figure 0

Claims (1)

[Scope of Claims] A video signal processing device that separates a video signal into a chroma signal and a luminance signal and processes each signal, comprising: a saturation detection circuit that detects the saturation level of the chroma signal; and the saturation detection circuit. a notch circuit that removes residual chroma signal components included in the luminance signal according to the saturation level of the chroma signal detected by the circuit; and selectively removes unnecessary chroma signal components included in the luminance signal. A video signal processing device characterized by: