JP2592924B2 - Video signal output device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video signal output device that outputs a video signal.

[Prior Art] Conventionally, a video tape recorder (hereinafter abbreviated as VTR) which records a video signal such as a television signal on a recording medium such as a magnetic tape or a magnetic disk and reproduces the video signal recorded from the recording medium. ), A still video system (hereinafter abbreviated as SV device), and the like.

In the above-described apparatus, when a color video signal is output during reproduction, a burst signal is added, and the monochrome video signal is output to an external monitor device without adding the burst signal.

[Problems to be Solved by the Invention] However, since each processing circuit inside the VTR or the SV device performs signal processing using the subcarrier signal fsc, a black and white video signal to be output is The leakage of the carrier signal fsc cannot be completely removed, and even if the black-and-white video signal is input to the monitor device, the automatic color saturation adjustment circuit (ACC circuit) in the monitor device leaks into the black-and-white video signal. The subcarrier signal fsc is detected, and the detected subcarrier signal fsc is amplified to a standard level.

As a result, the cross-color component of the black-and-white video signal is also amplified with the amplification of the fsc of the subcarrier signal. However, there is a problem that the cross color generated in the image becomes more conspicuous.

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

[Means for Solving the Problem] A video signal output device according to the present invention is a device capable of selectively outputting a color video signal and a black-and-white video signal, and outputs a color video signal or a black-and-white video signal. Output determining means for determining whether to output, and when the output determining means determines to output a color video signal, a first burst signal is added to the output color video signal and output; If it is decided to output a black and white video signal,
Video signal output means for adding a second burst signal having an amplitude level larger than that of the first burst signal added to the color video signal to the output black and white video signal and outputting the added signal.

[Operation] With the configuration described above, it is possible to add a second burst signal having an amplitude level larger than that of the first burst signal added to the color video signal to the black-and-white video signal and output the signal.

EXAMPLES 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 reproducing apparatus to which the present invention is applied as one embodiment of the present invention.

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

In the video signal recorded on the magnetic disk 1, a luminance signal is FM-modulated to a high frequency band, and a chrominance signal is composed of two types of color difference signals, that is, an RY signal and a BY signal are horizontally aligned. It appears alternately every scanning period, and the RY signal, B
After the -Y signal is converted to a known color difference line-sequential signal that is level offset from each other so that it can be identified during reproduction,
Further, the luminance signal is FM-modulated to a low frequency band and frequency-multiplexed with the FM-modulated luminance signal.

The magnetic disk 1 on which the video signal is recorded as described above is rotated at a predetermined rotation speed by the motor 2, and the magnetic head 3 is moved onto an arbitrary recording track of 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 amplified by a high-pass 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, and demodulates the luminance signal in the luminance FM demodulation circuit 7, and in the luminance de-emphasis circuit 8, reverses the emphasis processing performed during recording. After being subjected to the de-emphasis processing having the characteristics described above, the signals are supplied to the horizontal synchronizing signal separation circuit 9 and the skew compensation circuit 10.

The horizontal synchronizing signal separating circuit 9 separates the horizontal synchronizing signal from the signal output from the luminance de-emphasis circuit 8,
The separated horizontal synchronizing signal is supplied to the luminance skew compensating circuit 10, and the luminance skew compensating circuit 10 synchronizes the supplied horizontal synchronizing signal with the luminance de-emphasis circuit 8.
After the skew compensation is performed on the luminance signal output from the multiplexor, the luminance signal is supplied to the adder 11.

On the other hand, the BPF 6 separates a color difference line sequential signal FM-modulated from the reproduced video signal, demodulates it in a color difference line sequential FM demodulation circuit 12, and then a color difference line sequential de-emphasis circuit 13
In, after the de-emphasis processing having the opposite characteristics to the emphasis processing performed at the time of recording is performed,
The signals are supplied to a color difference determination circuit 14 and a color difference synchronization circuit 15.

The color difference discrimination circuit 14 is supplied with a horizontal synchronization signal separated by the horizontal synchronization signal separation circuit 9 in addition to the color difference line sequential signal supplied as described above. In synchronization with the signal, the offset level of the supplied color difference line-sequential signal is sampled, and the sampled level is compared with a reference level, so that the supplied color difference line-sequential signal is an RY signal or a B-line signal.
It is determined whether the signal is a Y signal, and a determination signal D indicating the determination result is output to the color difference synchronization circuit 15.

The color difference determination 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 black and white video signal. In the case of a signal, since a color difference line-sequential signal exists, a determination result indicating an RY signal and a determination result indicating a BY signal are obtained alternately in synchronization with a horizontal synchronization period. In the case where the video signal reproduced by 3 is a black-and-white video signal, since there is no color difference line-sequential signal, the determination result indicating the RY signal and the determination result indicating the BY signal alternate every horizontal synchronization period. The color difference discrimination signal is output as a high-level black and white / color discrimination signal BW / C when the video signal reproduced by the magnetic head 3 is a color video signal. Signal place Outputting a monochrome color determination signal BW / C at a low level to.

Next, the color difference synchronizing circuit 15 synchronizes the supplied color difference line-sequential signals according to the discrimination signal D output from the color difference discriminating circuit.

That is, the color difference synchronizing circuit 15 has a delay circuit for delaying the color difference line sequential signal output from the color difference line sequential de-emphasis circuit 13 by one horizontal synchronization period, and the RY signal and the BY signal are respectively delayed. The chrominance signal and the undelayed signal are switched and output in accordance with the discrimination signal D output from the color difference discrimination circuit 14 to be synchronized with the RY signal and the BY signal. Supplied to

The color difference skew compensation circuit 16 skews the RY signal and the BY signal supplied from the color difference synchronization circuit 15 in synchronization with the horizontal synchronization signal separated from the luminance signal in the horizontal synchronization signal separation circuit 9. After the compensation is performed, the compensation 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, and a carrier signal fsc generated by a carrier signal oscillator 19. The RY signal and the BY signal supplied from the color difference skew compensation circuit 16 are quadrature quadrature-modulated using the carrier signal fsc, and the carrier signal is supplied during a period defined by the burst flag pulse. A chroma signal C is formed by adding a burst signal synchronized with fsc and output.

After the DC component of the chroma signal C output from the encoder 17 is removed by the capacitor 20,
It is supplied to the terminal on the H side in FIG.

The carrier signal fsc is also supplied to the attenuator 24.
Is larger in amplitude than the burst signal added to the chroma signal C output from the encoder 17 (for example, about 1.5
The amplitude is adjusted so as to make the output double, and after the DC component is removed by the capacitor 25, it is supplied to the terminal on the H side in the figure of the switch 27.

A constant voltage source 22 is connected to a terminal on the L side of the switch 27 in the drawing.
And a switch 27 is controlled by a burst flag pulse output from the burst flag generation circuit 18.

That is, when the burst flag pulse is at the high level, the switch 27 is connected to the H side in the figure, and during the period corresponding to the period during which the burst signal is added to the chroma signal C output from the encoder 17, the attenuator 24 is connected.
, A burst signal whose amplitude has been adjusted so as to be larger than the normal chroma signal C is output, and when the burst flag pulse is at a low level, the switch 27 is set to L in FIG.
Side, and a signal of a constant voltage is output from the constant power supply 22.

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

By the way, the signal output from the constant voltage source 22 is a resistor
It is supplied as a bias to the capacitors 20 and 25 via 21, 26, respectively.

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

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

As described above, the luminance signal is supplied from the luminance skew compensation circuit 10 to the adder 11, and the adder 11 adds the luminance signal and the signal supplied from the switch 23 as described above. To form and output a color television signal or a black and white television signal.

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

In a monitor device, when a color television signal is input, a 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 of the separated chroma signal, it is decoded into RY and BY signals and supplied to a matrix circuit together with a luminance signal separated from the input color television signal. A color image is projected on the CRT based on the R, G, and B signals.

If a black and white television signal is input, AC
The presence or absence of a burst signal is detected by the C circuit, and when a carrier signal component is not detected in the burst portion, a black-and-white image is displayed on the CRT by not supplying a color difference signal to the matrix circuit.

By the way, when a carrier signal component leaks into a burst portion of a black and white television signal and the leaked carrier signal component is detected by the ACC circuit, the detected carrier signal component becomes a predetermined amplitude level. ACC
This increases the gain for the carrier signal component of the black-and-white television signal to the circuit, and further supplies the signal corresponding to the color difference signal component to the matrix circuit, so that the black-and-white image projected on the CRT is generated particularly at the edge of the image. Cross color is emphasized.

Therefore, by adding a burst signal having a larger amplitude level to the black and white television signal to the black and white television signal as in the above-described embodiment, the monitor device can convert the black and white television signal into a color television signal. Although it will be displayed incorrectly as a signal, since the amplitude level of the burst signal is larger than usual, the gain for the carrier signal component controlled by the ACC circuit can be kept smaller than usual, so the black and white image on the Braun tube can be displayed. The generated cross color is reduced.

As described above, in the present embodiment, when the video signal reproduced from the magnetic disk as the recording medium is a black-and-white video signal, the amplitude level is lower than that of the burst signal to which the color video signal is added. By adding and outputting a large burst signal, it is possible to reduce the cross color generated when displaying a black and white image on the monitor device.

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

[Effects of the Invention] As described 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 little image quality deterioration due to cross color. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a still video reproducing apparatus to which the present invention is applied, as one embodiment of the present invention. 14 ... Color difference discriminating circuit, 17 ... Encoder, 18 ... Burst flag generating circuit, 19 ... Carrier signal oscillator, 24 ... Attenuator, 23,27 ... Switch.

Claims (1)

(57) [Claims] 1. An apparatus which can selectively output a color video signal and a black-and-white video signal, comprising: output determination means for determining whether to output a color video signal or a black-and-white video signal; If the decision means decides to output a color video signal, the first burst signal is added to the output color video signal and output, and if it is decided to output a black and white video signal, And video signal output means for adding a second burst signal having an amplitude level larger than that of the first burst signal added to the color video signal to the output black and white video signal and outputting the added signal. Video signal output device.