JPS60163593A - Recording and reproducing device of video signal - Google Patents

Abstract

PURPOSE:To suppress edge noise and to reduce the quantity lost by ripple and to realize a picture with excellent quality by diversing the energy of an edge and reducing an amount of overshoots at the time of recording. CONSTITUTION:An AGC circuit 2 at the recording side of a recording and reproducing device absorbs the variance of input level of an input video signal, and an LPF3 removes a chroma signal. A recorded video phase equalizer circuit 101 is provided between the LPF3 and a dynamic emphasis circuit 7 to emphasize a high band component of the posterior video signal, and an edge part is applied with preshoot. The video signal having reduced overshoot quantity of the edge is converted into an angle modulation signal by an angle modulation circuit 10, and recorded on a magnetic tape 21. A chroma signal is removed at the reproduction side of an HPF25 and a reproduction signal is demodulated by an FM demodulator 31. A reproduction video phase equalizer circuit 102 is provided between the demodulator 31 and a dynamic de-emphasis circuit 34 and conducts overshooting of an edge at the reproduction side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the reproduction image quality of a magnetic recording and reproducing apparatus, and particularly to a video signal recording/writing apparatus suitable for improving edge image quality.

[Background of the invention]

A basic block diagram of a conventional VTR recording/reproducing circuit is shown in FIG. In FIG. 1, 1 is an input terminal for an image signal;
2 is an AGC amplifier for adjusting the input video signal to a constant value, 3 is an LPF for controlling unnecessary bands, 4 is a luminance comb filter that extracts only the luminance signal from the high frequency signal, and 6 is the DC level of the video signal. Keyed clamp circuit that fixes at the peak potential of the synchronous part, 7 is a dynamic emphasis,
8 is a main emphasis system, 9 is a clip circuit that defines the video level to prevent overmodulation, 10 is an angle modulation circuit, 11 is a spurious removal HPF 112 is a recording amplifier, and 13 is a BPF that extracts only the chroma signal from the video signal.
, 14 is an AC for adjusting the level of the burst signal of the video signal.
O115 is a dynamic emphasis circuit for the chroma signal, 16 is a burst emphasis circuit that emphasizes only the burst signal, 17 is a converter that converts the +1.58MHz chroma signal to a low band, 18 is a conversion carrier generation circuit, 19 is an LPF for spurious removal, and 20 is a Video head, 21 is a magnetic tape, 22 is a preamplifier, 23 is a switching amplifier, 24 is a buffer amplifier, 25 is an HPF for extracting the FM brightness signal, 26 is a reproduction FM equalizer, 2
7 is an AGC amplifier for adjusting the two head output signals (YFM) to constant values, 28 is an inversion suppression circuit, 29
is a dropout compensation circuit that replaces dropout with a pre-IH signal; 30 is an IH delay line; 31 is an FM demodulator;
32 is a main de-emphasis circuit, 33 is a spurious removal LPF 134 is a dynamic de-emphasis circuit, 35 is a noise cancellation circuit that suppresses high frequency and small amplitude signals, 36 is a mixing circuit for the reproduced luminance signal and chroma signal, and 37 is from the tape. 38 is a BPF that extracts only the chroma signal from the reproduced signal.
, a converter for returning to 58 MHz, 39 a circuit for generating conversion carriers, 40 a BP for spurious removal
F, 41 is an ACC amplifier for adjusting the level of each color burst signal to a constant value, 42 is for crosstalk removal (rectangular filter, 44 is a dynamic de-emphasis circuit for chroma signal, 45 is for compressing only the burst signal by 6 dB) A burst de-emphasis circuit 46 is an output terminal for a video signal.

The signal circuit block diagram in Fig. 1 shows the general configuration of a VTi (, but the problem in Fig. 1 is that the clip 9 is used to prevent overvariation of the FM modulator. This will be explained with reference to Figure 2. When a video signal as shown in (a) in Figure 2 is input as an input signal, the dynamic emphasis 7 and main emphasis 8 in Figure 1 emphasize the high frequency range, and the edge rises. is as shown in FIG.
, limited by dark clips ('D clips). Therefore, the energy in the shaded area in the figure is lost, and the edges of the reproduced waveform become dull as shown in (C) in the figure.

Furthermore, the edge noise in the edge portion worsens as the level near the white carrier increases due to overshoot. This edge noise, unlike flat area noise, cannot be reduced by processing such as a noise canceling circuit.

Therefore, this deterioration in edge image quality cannot be addressed by conventional techniques.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a video signal recording and reproducing apparatus that reduces waveform deterioration and noise at edges, which have been problems in the past, and realizes high-quality images.

[Summary of the invention]

In order to solve this problem, the present invention suppresses edge noise by dispersing energy at edges and reducing the amount of overshoot during recording, and further reduces waveform deterioration by reducing the amount lost due to clipping. suppress.

Furthermore, on the playback side, oversheeting is performed to emphasize the rise of edges, thereby improving the rise without increasing edge noise.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Third
In the figure, 101 is a recording video phase equalization circuit for dispersing oversheeting of edge portions by oversheeting during recording, and 102 is a reproduction video phase equalization circuit for emphasizing the rise of edge portions during reproduction. The other parts are the same as in FIG. The feature of FIG. 3 is that a recording video phase equalization circuit 101 is provided before the clip on the recording side, and a reproduction video phase equalization circuit 102 is provided on the reproduction side.

The recording video phase equalization circuit will be explained with reference to FIGS. 4 and 5. FIGS. 4(a) and 4(b) show a specific example of a recording video phase equalization circuit, in which 110 is a video signal input terminal, 111, 119 are transistors, 112° 114.1
17 is a resistor, 113 and 118 are capacitors, and 116 is an output terminal. In the WJ4 diagram (b), a transistor 119 is connected to avoid the influence of stray capacitance of the collector of the transistor 111. The circuit shown in Figure 4 is
The waveform response is changed depending on the phase characteristics, and the characteristics are determined by the resistors 112, 114 . It can be changed not only by the capacitor 113 but also by the resistor 117 and the capacitor 118.

The effect of FIG. 4 will be explained with reference to FIG. When a signal waveform as shown in FIG. 5(a) is input from the terminal 110 in FIG. Ru. This signal passes through the dynamic emphasis 7, the main emphasis 8, and the clip 98 in FIG. 3, so that it becomes as shown in FIG. 5(C). By making the edge part oversheet, the amount of oversheeting is reduced compared to the conventional waveform response (FIG. 2(b)). Therefore, the portion lost due to clipping is small, the waveform distortion of the reproduced waveform is also small, and edge noise is also suppressed, as shown in FIG. 5(d). However, the problem here is that, as shown in the figure, a bridge beat remains in the external waveform. A certain amount of preshoot will improve the sharpness, but if the preshoot is too strong it will degrade the image quality.

Providing a recording video phase equalization circuit as shown in Figure 4 during recording produces the effect of reducing edge noise (2) (Improvement of edge waveform distortion), but the recording video phase equalization circuit alone does not improve the reproduction waveform. Leads to pre-shading.

In order to solve this problem, a reproduction video phase equalization circuit 102 is provided on the reproduction side to suppress the pre-sheet during reproduction. The exogenous video phase equalization circuit will be explained with reference to FIGS. 6, 7, and 8. FIG. 86 shows a specific example of a reproduced video phase equalization circuit. In FIG. 6, 120 is an input terminal, 121 is a transistor, 122, 125, 126 is a resistor, and 123
The inductor 124 is a capacitor, and 127 is an output terminal. Figure 7 shows an example of the characteristics of a playback video phase equalization circuit.The frequency characteristics of the gain are approximately 200 ns at 2 MHz compared to the low frequency band. The effect of FIG. 6 will be explained with reference to FIG. 8 in which the waveform response changes. When a reproduction signal like that shown in FIG. 8(a) (external waveform when a recording video phase equalization circuit is provided) is input from the terminal 120 in FIG.
7, a signal waveform in which the edge portion is overshaded and the preshoot is suppressed is output as shown in FIG. 7(b). Furthermore, the playback video phase equalization circuit has a flat gain within the band, so edge noise is not emphasized. Therefore, the edge noise can improve the waveform response of the edge portion at its tt.

To summarize the above, the present invention uses a recording video phase equalization circuit to pre-sheet the overshoot of the edge rising portion during recording, thereby reducing the level of white carrier interference caused by overshading and reducing the edge level. Check the S/N of the department.

(2) The amount of suppression by clipping is reduced by converting it to a pre-sheeted sheet, and waveform distortion is improved.

Furthermore, during playback, the playback video phase equalization circuit (1) overshoots the playback waveform that has been preshaded due to the influence of the recording video phase equalization circuit, and rewrites the rise of the edge portion;

This makes it possible to improve the waveform response and edge noise at the edge, which have been problems in the past. by the way,
The location of the recording video phase equalization circuit in FIG. 3 is not limited to the illustrated location. For example, it can be provided after the keyed clamp circuit 6.

Furthermore, the reproduction video phase equalization circuit 102 can be omitted by providing the LPF 1a with group delay characteristics as shown in FIG.

〔Effect of the invention〕

According to the present invention, edge noise can be suppressed and edge waveform distortion can be improved by preshooting edge portions during recording. Furthermore, by making the reproduction side open neat, edge rise can be improved without increasing edge noise.

The above has the effect of improving edge image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the signal system of a conventional VTR, FIG. 2 is a waveform diagram of each part of the conventional signal system, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. A specific circuit diagram of the recording video phase equalization circuit of the present invention, FIG. 5 is a waveform diagram of each part of the present invention, FIG. 6 is a specific circuit diagram of the reproduction video phase equalization circuit of the present invention, and FIG. 8 is a characteristic diagram of the reproduced video phase equalization circuit, and FIG. 8 is a waveform diagram of each part of the present invention. 1...Video signal input terminal. 7...Dynamic emphasis circuit. 8... Main emphasis circuit. 9... Clip circuit, 20... Magnetic head. 21... Magnetic tape, 33... L P P46...
・C/YMix circuit. 101... Recording video phase equalization circuit. 102... Reproduction video phase equalization circuit. 2nd Moku 1-W Cliff 0 4th Ward (a) Ding- Ngong 6th Brother 70th

Claims (1)

[Claims] AG that absorbs input level variations of video signals on the recording side
C circuit, an LPF that removes the chroma signal, a clamp circuit that fixes the peak potential of the synchronization signal, a pre-emphasis circuit that emphasizes the high-frequency components of the video signal, and a A clip circuit that limits the amplitude, an angle modulation circuit that converts the output signal of the clip circuit into an angle modulation signal, a recording amplifier circuit that amplifies the converted signal, and a magnetic head that records the amplified signal on a magnetic tape. Furthermore, on the playback side, a playback amplification circuit that amplifies the signal played back from the magnetic tape by the magnetic head;
An HPF that removes chroma signals, an AGC circuit that absorbs playback level variations, an inversion suppression circuit that prevents inversion phenomena, and a demodulation circuit that demodulates angle-modulated playback signals.
In a video signal recording and reproducing apparatus having a de-emphasis circuit having a characteristic opposite to the pre-emphasis characteristic during recording, the recording side is provided with at least a first circuit for pre-shooting edges, and the reproducing side is provided with a first circuit for pre-shooting edges. A video signal recording and reproducing device characterized by comprising a second circuit that performs overshooting.