JPH04150289A - Video signal recorder - Google Patents

Abstract

PURPOSE:To prevent production of smear or the like by providing an emphasis circuit and a clip circuit clipping an output of the emphasis circuit at a level between a peak value of a chrominance signal outputted from the emphasis circuit and a peak value of a luminance signal to the recorder. CONSTITUTION:An output of a time axis signal processing circuit 4 is inputted to an emphasis circuit 5, after its high frequency component is emphasized, the result is inputted to a clip circuit 6. The clip circuit 6 has variable resistors 7, 8 to set and adjust a white clip level and a dark clip level and a video signal clipped at the white clip level and the dark clip level by the clip circuit 6 is inputted to an FM modulator 9, in which the signal is FM-modulated and the modulated signal is recorded on a magnetic tape 11. Then the clip level is set to a value between the peak value of a chrominance signal and the peak value of a luminance signal and then the clipping of the luminance signal is prevented. Then the production of smear is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal recording device suitable for use in a video tape recorder that records and reproduces high-definition television signals.

[Prior Art] When recording a video signal on a magnetic tape, the video signal is usually FM modulated. To improve SN, the video signal is FM
emphasized before.

When this emphasis is applied, areas generally called whiskers occur in areas where the level changes rapidly, and their peak values become extremely large. If the absolute value level of the peak value of this video signal is too large, a so-called inversion phenomenon occurs. To prevent this, signals above a predetermined level (white clip level) and signals below a predetermined level (dark clip level) are clipped.

[Problem to be Solved by the Invention 1] As described above, since the conventional device clips a part of the luminance signal, there is a problem that the clipped information is lost and waveform distortion such as smear occurs. This smear phenomenon occurs on the screen, for example, when there is an image of a horizontal black band, a black shadow appears on the outside of the edge.

The present invention was made in view of this situation, and is intended to prevent the occurrence of smears and the like.

[Means for Solving the Problems] The video signal recording device of the present invention is a video tape recorder that time-division multiplexes color signals and luminance signals and performs FM recording. The present invention is characterized by comprising a clip circuit that clips the output of the emphasis circuit at a level between the peak value of the output color signal and the peak value of the luminance signal.

[Function] In the video signal recording device having the above configuration, the clip level is set to a value intermediate between the peak value of the luminance signal and the peak value of the color signal. Therefore, clipping of the luminance signal can be prevented, and the occurrence of smear can be suppressed.

[Embodiment] FIG. 1 is a block diagram showing the configuration of an embodiment of a video tape recorder to which the video signal recording device of the present invention is applied.

Input terminals 1 to 3 have a luminance signal Y and a color difference signal Pa (
A color difference signal PR (RY) and a color difference signal PR (RY) are respectively input. For each horizontal scanning line, the time axis signal processing circuit 4
The color difference signal and luminance signal are time-division multiplexed. Further, in the color difference signal, PR and P8 are arranged alternately in line sequence.

The output of the time-domain signal processing circuit 4 is input to an emphasis circuit 5, and after its high frequency components are emphasized, the output is input to a clip circuit 6. The clip circuit 6 has a variable resistor 7.8 for setting and adjusting the white clip level and the dark clip level. The video signal clipped by the clip circuit 6 at the white clip level and the dark clip level is input to the FM modulator 9 and subjected to FM modulation. The output of the FM modulator 9 is amplified by an amplifier 10, then supplied to a magnetic head 11, and recorded on a magnetic tape (not shown).

Similar to the above A-azimuth system emphasis circuit 5 to magnetic herad 11, B-azimuth system emphasis circuit 15
A magnetic head 21 is provided. FM video signals can be recorded on two tracks (one segment) at the same time using the two-channel discs 11 and 21.

A rotating drum (not shown) has a pair of magnetic heads 11.
In addition to 21, another pair of heads are provided 180 degrees apart, and the rotating drum is rotated at twice the standard speed (1800 rpm) (3600 rpm). the result,
A video signal of one frame (two fields) is distributed and recorded into four segments (eight tracks).

Next, with reference to FIG. 2, the operation of the clip circuit 6.16 will be briefly described.

The time division multiplexed signal output from the time axis signal processing circuit 4 (
TDM signal) is shown by a solid line in FIG. That is, after the horizontal synchronization signal and the color burst signal, the color difference signal PB or PR, and then the luminance signal Y.
It is located. This TDM signal is the emphasis circuit 5
When the signal is emphasized by , as shown by the broken line in the figure, a portion that can be called a whisker occurs in a portion where the level changes rapidly. The height of this whisker approximately corresponds to the amplitude of the changing portion (TC+ in the case of the color difference signals PB and PR, TY in the case of the luminance signal Y). The white clip level in the clip circuit 6.16 is the positive peak value of the color difference signal (in the case of the embodiment, the white clip level is 27 in the positive direction from the pedestal level).
C) and the positive peak value of the luminance signal (in the case of the embodiment, the level 2TY in the positive direction from the pedestal level). The dark clip level is defined by the negative peak value of the color difference signal (in the case of the example, the level of TC in the negative direction from the pedestal level) and the negative peak value of the luminance signal (in the case of the example, the negative peak value of the luminance signal in the negative direction from the pedestal level). It can be set to a predetermined level in the interval B, which is between the TY level and the TY level.

Therefore, the whiskers of the color difference signal are clipped, but the whiskers of the luminance signal are not clipped.

Note that the amplitude TC of the color difference signal is set to a larger value than the amplitude TY of the luminance signal. This is because a color difference signal requires a higher S/N ratio than a luminance signal in terms of visibility, and the distortion of the luminance signal is more noticeable than that of the color difference signal.

As described above, since color difference No. 43 has a larger amplitude, the inversion phenomenon due to overmodulation is more likely to occur. Therefore, this is clipped at a predetermined level. On the other hand, the brightness signal has a correspondingly larger margin against overmodulation.

However, in the case of a normal image, the amplitude of the color difference signal rarely increases, so the probability that the color difference signal actually clips is low. Therefore, if the color difference signal is also clipped, smear will occur, but for the above reason, the possibility that smear will actually occur is reduced.

FIG. 3 shows more specific waveforms of the outputs of the emphasis circuits 5 and 15.

It can also be seen from the figure that only the whiskers of the color difference signal are clipped, and the whiskers of luminance No. 48 cannot be clipped.

In the above description, the luminance signal Y has color difference signals P, , P□
Although the color signals R, G, and B are time-division multiplexed,
The present invention can also be applied to the case where the luminance signal is time-division multiplexed.

[Effects of the Invention] As described above, according to the video signal recording device of the present invention, the clip level is set between the peak value of Color No. 48 and the peak value of the luminance signal, so that the clip level is set between the peak value of Color No. 48 and the peak value of the luminance signal. It is possible to suppress the occurrence of the inversion phenomenon, and in particular to prevent the clipping of the luminance signal (substantially also the clipping of the color signal), thereby suppressing the occurrence of smear.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a video tape recorder to which the video signal recording device of the present invention is applied, and FIG.
3 and 3 are waveform diagrams illustrating the operation of the clip circuit of FIG. 1. 4... Time axis signal processing circuit, 5, 15... Emphasis circuit, 6, 16... Clip circuit, 9, 19...
・FM modulator.

Claims (1)

[Scope of Claims] A video tape recorder that performs FM recording by time-division multiplexing a color signal and a luminance signal, comprising: an emphasis circuit that emphasizes the color signal and the luminance signal; and a peak of the color signal output from the emphasis circuit. A video signal recording device comprising: a clip circuit that clips the output of the emphasis circuit at a level between the peak value of the luminance signal and the peak value of the luminance signal.