JPH0279579A - Video signal output device - Google Patents

Abstract

PURPOSE:To output a black/white signal with less picture quality deterioration due to cross color by adding a burst signal having a larger amplitude level than a burst signal added to a color video signal to a black/white video signal and outputting the result. CONSTITUTION:The amplitude of the carrier signal fsc fed to an atteuator 24 is adjusted so as to increase more than that of a burst signal added to a chroma signal C outputted from an encoder 17 and outputted and after the DC component is eliminated by a capacitor 25 and fed to a terminal at H position of a switch 27. When a black/white color discrimination signal BW/C is at a low level, the signal outputted from the switch 27 is fed to an adder 11 to form a black/white television signal and outputted. Thus, since the gain to the carrier signal component controlled by an ACC circuit is suppressed smaller normally, the cross color generated on the white/black picture on a cathode ray tube is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal output device that outputs a video signal.

[Prior Art] Video tape recorders (hereinafter abbreviated as VTRs) have traditionally recorded video signals such as television signals on recording media such as magnetic tapes or magnetic disks, and reproduced the recorded video signals from the recording media. ) and still video systems (hereinafter abbreviated as Sv devices) are known.

In the above-mentioned apparatus, when outputting a color video signal during reproduction, a burst signal is added, and a monochrome video signal is outputted to an external monitor device or the like without adding the burst signal.

[Problems to be Solved by the Invention] However, since each processing circuit inside the VTR or Sv device performs signal processing using the subcarrier signal fsc, the subcarrier signal fsc is It is not possible to completely eliminate leakage of the carrier signal fsc, and even if the monitor device converts the black and white video signal manually, the automatic color saturation adjustment circuit (ACC circuit) in the monitor device converts the black and white video signal into the black and white video signal. subcarrier signal fc
s is detected, and the detected subcarrier signal f
SC will be amplified to standard level.

As a result, the cross color component of the black and white video signal is also amplified along with the amplification of the subcarrier signal fsc, so on the screen of the monitor device, the cross color component of the black and white video signal is compared to the cross color that occurs in the color video signal. A problem has arisen in that the cross color that occurs is more noticeable.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a video signal output device capable of outputting a black and white video signal with less deterioration in image quality due to cross color.

[Means for solving the problem] The video signal output device of the present invention is a device that can selectively output a color video signal No. 8 and a black and white video signal, and the burst signal added to the color video signal. a first burst signal forming means for forming a first burst signal having an amplitude level greater than , an output determining means for determining whether to output a color video signal or a monochrome video signal, and in the output determining means, a first burst signal adding means for adding a first burst signal formed by the first burst signal forming means to the output black and white video signal when it is determined to output the black and white video signal; It is equipped with the following.

[Operation] With the above-described configuration, the first burst signal having a larger amplitude level than the burst signal added to the color video signal can be added to the monochrome video signal and output.

[Example] Hereinafter, the present invention will be described in detail using an example of the present invention.

FIG. 1 is a diagram showing a schematic configuration of a still video playback neck device to which the present invention is applied as an embodiment of the present invention.

In FIG. 1, video signals for one field are recorded in a plurality of recording tracks provided on concentric circles on a magnetic disk 1 for one recording track.

In the video signal recorded on the magnetic disk 1, the luminance signal is FM-modulated in a high frequency band, and the color signal is composed of two types of color difference signals, namely, the R-Y signal and the B-Y signal, which are arranged horizontally. The R-Y signal, B
5 after the Y signal is converted into the well-known color difference line sequential signal whose level is offset from each other so that it can be distinguished during playback.
Furthermore, it is FM-modulated in a low frequency band and frequency-multiplexed with the FM-modulated luminance signal.

The magnetic disk 1 on which video signals are recorded as described above is rotated by a motor 2 at a predetermined number of rotations, and the magnetic head 3 is moved onto an arbitrary recording track on the magnetic disk 1 by a head moving mechanism (not shown). The recorded video signal is reproduced by the magnetic head 3.

The video signal reproduced by the magnetic head 3 is amplified by a reproduction amplifier 4 and then passed through a bypass filter (HPF) 5.
, is supplied to a band pass filter (BPF) 6.

Then, the HPF 5 separates the FM-modulated luminance signal from the reproduced video signal, demodulates it in the luminance FM demodulation circuit 7, and then sends it to the luminance de-emphasis circuit 8, which is the opposite of the emphasis processing performed during recording. After being subjected to de-emphasis processing having the characteristics shown in FIG.

The horizontal synchronization signal separation circuit 9 separates the horizontal synchronization signal from the signal output from the luminance de-emphasis circuit 8, and the separated horizontal synchronization signal is supplied to the luminance skew compensation circuit 10, which includes: In synchronization with the supplied horizontal synchronizing signal, the luminance signal output from the luminance de-emphasis circuit 8 is subjected to skew compensation and then supplied to the adder 11.

On the other hand, the BPF 6 separates the FM-modulated color difference line sequential signal from the reproduced video signal, and after demodulating it in the color difference line sequential FM demodulation circuit 12, the color difference line sequential de-emphasis circuit 13 performs de-emphasis during recording. After de-emphasis processing, which has characteristics opposite to those of emphasis processing, is performed, the signal is supplied to a color difference discrimination circuit 14 and a color difference synchronization circuit 15.

In addition to the color difference line sequential signal supplied as described above, the color difference discrimination circuit 14 is also supplied with a horizontal synchronization signal separated by the horizontal synchronization signal separation circuit 9. In synchronization with the horizontal synchronization signal, the offset level of the supplied color difference line sequential signal is sampled,
By comparing the sampled level with the reference level, it is possible to determine whether the supplied color difference line sequential signal is a R-Y signal or a B signal.
-Y signal, and outputs the result of the determination (number a1) to the color difference synchronization circuit 15.

The color difference discrimination circuit 14 also has a function of determining whether the video signal reproduced by the magnetic head 3 is a color video signal or a monochrome video signal. In the case of a video signal, since a color difference line sequential signal exists, a discrimination result indicating the R-Y signal and a discrimination result indicating the B-Y signal are obtained alternately in synchronization with the horizontal synchronization period. When the video signal reproduced by HERADO 3 is a black and white video signal, there is no color difference line sequential signal, so the determination result indicating the R-Y signal and the determination result indicating the B-Y signal are different for each horizontal synchronization period. Taking advantage of the fact that the color difference discrimination signal cannot be obtained alternately, when the video signal being reproduced by the magnetic head 3 is a color video signal, the color difference discrimination signal outputs a high level black and white/color discrimination signal BW/C, In the case of a black and white video signal, a low level black and white color discrimination signal BW/C is output.

Next, the color difference synchronization circuit 15 synchronizes the supplied color difference line number 18 in accordance with the discrimination signal outputted from the color difference discrimination circuit.

That is, the color difference synchronization circuit 15 has a delay circuit that delays the color difference line sequential signal outputted from the color difference line sequential de-emphasis circuit 13 by one horizontal synchronization period,
The signals are synchronized into the R-Y signal and the B-Y signal by switching and outputting the delayed signal and the non-delayed signal in accordance with the discrimination signal output from the color difference discrimination circuit 14, respectively. The signal is supplied to the color difference skew compensation circuit 16.

The color difference skew compensation circuit 16 receives the R-Y signal and the a-Y signal 1s- supplied from the color difference synchronization circuit 15.
After performing skew compensation in synchronization with the horizontal synchronizing signal separated from the moderation signal in the horizontal synchronizing signal separation circuit 9, it is supplied to the encoder 17.

The encoder 17 further includes a burst flag pulse output from a burst flag generation circuit 18 in synchronization with the horizontal synchronization signal separated by the horizontal synchronization signal separation circuit 9;
Carrier wave signal fsc generated by carrier wave signal oscillator 19
The R-Y signal and B-Y signal supplied from the color difference skew compensation circuit 16 are converted into a carrier wave signal fs.
A chroma signal C is formed and output by carrying out quadrature two-phase modulation using the carrier wave signal fsc and adding a burst signal synchronized with the carrier wave signal fsc during a period defined by the burst flag pulse.

The chroma signal C output from the encoder 17 has its DC component removed by a capacitor 20, and then is supplied to the H side terminal of the switch 23 in the figure.

Further, the carrier wave signal fsc is also supplied to the attenuator 24, and the attenuator 24 receives the input carrier wave signal fsc with an amplitude larger than that of the burst signal added to the chroma signal C output from the encoder 17 (for example, about 1 After the DC component is removed by a capacitor 25, the signal is supplied to the H side terminal of the switch 27 in the figure.

In addition, a constant voltage source 2 is connected to the L side terminal of the switch 27 in the figure.
A constant voltage signal is supplied from switch 2, and switch 2
7, the switching operation is controlled by a burst flag pulse outputted from the burst flag generating circuit 18.

That is, when the burst flag pulse is at a high level, the switch 27 is connected to the H side in the figure, and the encoder 17
During the period corresponding to the period in which the burst signal is added to the chroma signal C output from the attenuator 24, a burst signal whose amplitude is adjusted to be larger than that of the normal chroma signal C is output, and the burst signal is When the flag pulse is at a low level, the switch 27 is connected to the L side in the figure, and a constant voltage signal is output from the constant power source 22.

As described above, the signal output from the switch 27 is supplied to the L side terminal of the switch 23 in the figure.

Incidentally, the signal outputted from the constant voltage source 22 is supplied as a bias to the □ capacitor 20 and the capacitor 25 via resistors 21 and 26, respectively.

The switching operation of the switch 23 is controlled by the monochrome/color discrimination signal BW/C output from the color difference discrimination circuit 14.

That is, as described above, the color difference discrimination circuit 14 outputs a high level monochrome/color discrimination signal BW/C when the video signal reproduced by the magnetic head 3 is a color video signal; outputs a low-level black-and-white/color discrimination signal BW/C, so the switch 23 to which this black-and-white/color discrimination signal BW/C is supplied is a monochrome/color discrimination signal BW/C.
When the color discrimination signal gW/C is at a high level, H in the figure
The chroma signal C output from the encoder 17 is supplied to the adder 11, and the black/white/color discrimination signal B is output from the adder 11.
When W/C is at a low level, it is connected to the L side in the figure, and a signal output from switch 27 is supplied to adder 11.

Further, as described above, the brightness signal is supplied from the brightness skew compensation circuit 10 to the adder 11, and the adder 11 adds this brightness signal to the signal supplied from the switch 23 as described above. A color television signal or a black and white television signal is formed by □ and output.

The color or monochrome television signal output from the adder 11 is supplied to a monitor device (not shown).

When a color television signal is input to the monitor device, the burst signal is separated from the input color television signal, and an ACC circuit is used to separate the burst signal from the input color television signal so that the separated burst signal has a predetermined amplitude level. After controlling the gain for the separated chroma signal, it is decoded into R-Y and B-Y signals, which are supplied to a matrix circuit together with the luminance signal separated from the input color television signal, and are formed in the matrix circuit. A color image is projected on the cathode ray tube based on the R, G, and B signals.

Also, if a black and white television signal is input, the AC
The C circuit detects the presence or absence of a burst signal, and if no carrier signal component is detected in the burst portion, the matrix circuit is not supplied with a color difference signal, so that a black and white image is displayed on the cathode ray tube.

By the way, if a carrier wave signal component leaks into the burst part of a black and white television sweet signal and the leaked carrier wave signal component is detected by the ACC circuit, the detected carrier wave signal component is converted into a predetermined signal. In order to increase the amplitude level, the ACC circuit increases the gain for the carrier signal component of the black and white television signal, and since the matrix circuit is also supplied with a signal corresponding to the color difference signal component, the black and white displayed on the cathode ray tube increases. In the video, cross colors that occur particularly at the edges of the image are emphasized.

Therefore, by adding a burst signal with a larger amplitude level than the burst signal added to the color television signal to the black-and-white television signal as in the present embodiment described above, the monitor device can convert the black-and-white television signal to the color television signal. However, since the amplitude level of the burst signal is larger than normal, the gain for the carrier signal component controlled by the ACC circuit is suppressed smaller than normal, so the black and white image on the CRT is displayed incorrectly. The cross color that occurs will be reduced.

As explained above, in this embodiment, when the video signal reproduced from the magnetic disk that is the recording medium is a black and white video signal, the amplitude is lower than that of the burst signal added to the color video signal. By adding and outputting a burst signal with a high level, it becomes possible to reduce cross colors that occur when displaying black and white images on a monitor device.

In this embodiment, a still video reproducing apparatus to which the present invention is applied has been described as an example, but the present invention is not limited to this and can be applied to other apparatuses such as a VTR.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a video signal output device capable of outputting a black and white video signal with less deterioration in image quality due to cross color. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a still video playback device to which the present invention is applied, as an embodiment of the present invention. 14... Color difference discrimination circuit, 17... Encoder, 18
... Burst flag generation circuit, 19... Carrier wave signal oscillator, 24... Attenuator, 23.27... Switch.

Claims (1)

[Claims] A device capable of selectively outputting a color video signal and a monochrome video signal, the device forming a first burst signal having a larger amplitude level than the burst signal added to the color video signal. output determining means for determining whether to output a color video signal or a monochrome video signal; and a first burst signal forming means for determining whether to output a color video signal or a monochrome video signal; A video signal output device comprising: first burst signal adding means for adding a first burst signal formed by the first burst signal forming means to an output black-and-white video signal and outputting the resultant signal.