JPS60103893A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce considerably color unevenness and cross-cut noise compared with a conventional circuit even when an output variation due to short drop-out on a color burst and defective contact of a tape are generated during regeneration by making a color burst period of a regenerating signal longer. CONSTITUTION:After a chroma signal (b) is separated from a picture signal (a) by a band-pass filter 30, the picture signal (a) passes through a switch 31 and a phase adjustment circuit 32, and only a burst is sampled to input to a PLL circuit 33. A horizontal synchronizing signal is fed to a timing generating circuit 34 from a terminal 37, and the signal as shown by (c) is generated. The PLL circuit 33 generates a burst and a phase-locked signal (e), and outputs them to a switch 35. The switch 35 switches the signal (b) and the signal (e) at high speed by a signal (f) from the timing generating circuit 34, and outputs a composite signal (q) to a terminal 38. This means that a burst part of the input signal (b) is switched to the output from the PLL circuit, and outputted. Thus a color burst period recorded on a magnetic tape becomes about three times longer than that of a conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording/reproducing apparatus such as a video tape recorder using a carrier color signal low frequency conversion recording method.

Conventional configurations and their problems In recent years, video cheap recorders (hereinafter abbreviated as VTRs) have become widespread, but most of them have 1.

Recording and reproduction are performed using a carrier color signal low-frequency conversion recording method (hereinafter abbreviated as M method).

This M method has many advantages, such as: (1) the color signal is not affected by fluctuations in the reproduction time axis of the VTR; (2) the FM signal has a high frequency and bias-like function, so the color signal can be recorded and reproduced with good linearity. There is.

Here, block diagrams of conventional V and TR signal recording systems and reproduction systems are shown in FIGS. 1 and 2, respectively. Briefly, in FIG. 1, during recording, a luminance signal passes through a low-pass filter 1, is modulated by an FM modulator 2, passes through a bypass filter 3, and then is sent to a mixer 4. On the other hand, the color signal passes through a bandpass filter 5, an auto color control circuit (hereinafter abbreviated as ACC circuit), and an auto phase control circuit 6 (hereinafter abbreviated as APC circuit).
k and is modulated by a balanced modulator 7 and a low-pass filter 8.
After passing through the mixer 4, it is mixed with the luminance signal, and then
The signal is amplified by a recording amplifier 9 and sent to a recording head 10.

At the time of F-angle conversion, as shown in FIG. 2, the signal goes through almost the reverse process and is outputted to the output terminal 21 as a reproduced video signal. here,
Reference numeral 22 indicates a recording luminance signal system block, 23 a recording color signal system block, 24 a reproduction luminance signal system block, and 25 a reproduction color signal system block. Although the actual circuit is more complex, the operation of the signal system is well known, so I will only briefly describe it here.

Now, in the above-described configuration, the color burst converted to a low frequency band is recorded and reproduced with only about one and a half wavelengths. In other words, mud.

If a change in the appearance due to poor contact between the tape and the tape occurs during the reproduction period of one and a half wavelengths of the color burst, the above-mentioned APC and ACC circuits will not function satisfactorily, resulting in color unevenness. This appeared as horizontal noise on the monitor screen and was the most noticeable color noise.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a magnetic recording and reproducing apparatus that is capable of improving the S/N ratio of color signals and, in particular, significantly reducing horizontal fluctuation noise of reproduced color signals.

Structure of the Invention The magnetic recording and reproducing apparatus of the present invention separates a combined image (i3) into a luminance signal and a color signal, performs low frequency conversion on the color signal, frequency modulates the luminance signal, and generates the low frequency converted color signal. A magnetic recording device using a carrier color signal low-pass conversion recording method that mixes a frequency-modulated luminance signal and performs recording and reproduction on a magnetic recording medium-1-. P
It is equipped with an LL circuit, a switch for selecting one of the color codes at the output of the PLL circuit, and a timing pulse generation circuit for generating switching timing, and the color signal near the color burst is generated by the timing pulse. The signal from the generation circuit is replaced with the output of the PLL circuit to form a composite color signal, which is then converted to a low frequency signal and mixed with an FM modulated luminance signal and recorded. The color burst period recorded on the magnetic tape is about three times longer than the conventional one, meaning that the color burst converted to the low frequency range has about four wavelengths, so even if dropouts occur during burst playback, it will be longer than the conventional one. The APCl path and ACC circuit operate much more stably. In other words, color unevenness and horizontal noise are significantly reduced, and color signal S/
N is facing.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 (The formula is a recording system according to an embodiment of the present invention.

Figure 3 (B) shows a block diagram of the playback system. It is a thing,
It can be seen that FIG. 3(B) is the same as FIG. 2 with the burst period mute block 2Y added.

The burst period is expanded by the burst rebus period expansion block 26, and the burst period is muted to a regular length by the burst period mute block 27. Here, the conventional circuit pro, 22, 23, 24.
25 is unchanged except for some constants.

Next, details of the burst period expansion block 26 are shown in FIG. 4, and signal waveforms of various parts at this time are shown in FIG.

i4 figure U, bandpass filter 30, f; 411
Adjustment circuit 32, PLL circuit 33. The timing generation circuit 34 and switches 31 and 36 constitute (1G).

The video signal a input from the terminal 36 is separated from the chroma signal by the bandpass filter 30, passes through the switch 311 and the phase rA adjustment circuit 32, only the burst is extracted, and is input to the PLL circuit 33.

Here, a horizontal synchronizing signal is applied from the terminal 37 to the timing generating circuit 34, which outputs a signal as shown in C. PLL
1 path 33, 3,5795 phase locked with burst
45 generates a signal e of Ml and outputs it to the sui-nochi 35. The switch 36 switches the signals f, J, and signal e from the timing generation circuit 34 at high speed, and outputs a composite signal q to a terminal 38. In other words, the burst part of the input signal.

It will be output instead of the output from the PLL circuit. As shown in the waveform of the signal f, this switching period rises later than the falling edge of the horizontal synchronizing signal, and the burst II
, lj, which falls at the end of lj.

Next, a detailed block diagram of the burst period mute block 27 is shown in FIG. 6, and signal waveforms of each part are shown in FIG. 7.

In those drawings, the reproduced color signal 1 that enters the terminal 4° is muted by the muting circuit 43 during periods other than the regular burst period, and becomes a signal 1 (
It is mixed with the return signal j and outputted to the terminal 41 as a reproduced video signal e. Here, the input to the timing pulse generation circuit 42 is a horizontal synchronization signal, and the output) is a signal as shown in FIG. It is.

Next, the effects of the present invention will be explained in comparison with a conventional example.

To Figure 8, (B) shows a conventional example when noise occurs during the reproduction burst toy, -u) and +lj raw f according to the present invention.
A comparison was made with B). Here, al.

bl is the input tsubo 1 variable signal, a 2 and b 2 are the composite color signals after replacing the conventional color signal and the present invention, a
3°b3 is a low frequency converted color signal, 64. b 4(t
11R raw low range color without dropout 1. I issue,
a s , b s rt Waveform showing the dropout period, a e , b 6 is the 11th raw low range color signal when the dropout occurs, a 7. b 7 is 3
．． 579645 M IIZ color signal after converting to a high frequency, a a and b s indicate a heibo video signal after being mixed with a reproduced luminance signal.

In this comparative example, when dropout occurs, the conventional circuit hardly reproduces the color burst as shown in a6. In other words, the reproduced color signal shown in A is
Since the CC circuit and the APC circuit are not operating normally, the phase and gain are not guaranteed. In other words, color unevenness and horizontal noise will occur. On the other hand, in the circuit according to the present invention, as shown in b6, the four wavelengths of the color burst converted to the low frequency range are completely reproduced, so that the raw color signal shown at the mouth is guaranteed in both phase and gain. Especially Naru. No sharp color noise occurs. It can be seen that this significantly reduces color noise.

Na:11. -1-'' in FIG. 4 in two consecutive implementation rows.

The bandpass filter 30 may be omitted, but the phase adjustment circuit 32id: positioned after the PLL circuit 33 may be omitted. Of course, there are various things regarding the timing from the timing pulse generation circuit, lt, that-
An example is shown in FIG. In Fig. 9, a is the input signal, b is the timing pulse of the recording system, C is the composite color signal after being changed, d is the timing pulse of the reproduction system, e is the muted ILT raw color signal, f is the Heibo output signal. 3 Here, it is clear that b in FIG. 9 corresponds to fIc in FIG. 5, and d in FIG. 9 corresponds to 1 in FIG. 7.・In the embodiment, the ACC circuit of the conventional circuit, A
The time constant of the PC circuit may be changed to correspond to the duration of the timing pulse.

As is clear from the explanation in ``Effects of the Invention'', the magnetic recording and reproducing apparatus of the present invention prevents IXi drooping, knob-out, etc. from color burst -I- during reproduction in order to obtain a long period between color burst +01 of the reproduction signal. Even if output changes occur due to poor tape contact, the ACC and PC circuits operate stably, and compared to conventional circuits, color unevenness + 4J'I'i noise is greatly reduced. but? ! l1-) Experiments have confirmed that the color S/N can be improved by 2 dB1.

[Brief explanation of drawings]

Figure 1 is a block diagram of the recording system of a conventional example, and Figure 2! Bow - A conventional example of a drawing thread professional, Figure 3 (8), (B) is a block diagram of the recording system and the Heigo thread of an embodiment of the present invention, Figure 4 (
171: Verse 1 publication 1) 1 expansion used in the present invention, )(
A circuit configuration diagram showing an example of a block, FIG. 5 is a signal waveform diagram of each part in FIG. 4, FIG. 6 is a block diagram of a main part of the endogenous system of the present invention, FIG. Figure 8 (A) and (B) are waveform diagrams showing the ratio of the signal waveforms of the conventional example and the present invention. Figure 9 is a waveform diagram showing an example of the timing pulse in the present invention. 22...Recording luminance signal system professional, 7ri, 23...Recording telegraph system block, 24 -r1 raw luminance signal system block, 25-...Chinese color signal system block, 26-...Burst 101 Interval expansion block, 27 - Burst ItJI mute pro, 30 ・Band pass filter mi 32
- Phase adjustment circuit, 33-・PLL circuit, 34, 42
・・Timing pulse generation circuit, 43 ・・Muting circuit. Name of substitute Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 Figure 4 ? 5 Fig. 3 (A) 7 4th Akanegai 5 Fig. 6 Fig. 17 Ryo 8 Fig. (8) (B) α5-已-m b5-m-''l-- Fig. 9

Claims (3)

[Claims] (1) Separate the composite video signal into a luminance signal and a color signal, perform low frequency conversion on the color signal, frequency modulate the luminance signal, and mix the low frequency modified color signal and the frequency modulated luminance signal. , a magnetic recording and reproducing device using a carrier color signal low-frequency conversion recording method for recording and reproducing information on a magnetic recording medium, which comprises a phase-locked loop circuit that synchronizes with a color burst of a color signal, an output of the phase-locked loop circuit, and a phase-locked loop circuit synchronized with a color burst of a color signal; It is equipped with a switch for selecting one of the above color signals and a timing pulse generation circuit that generates the switching timing, and outputs the color signal near the color burst to the phase lock loop circuit according to the signal from the timing pulse generation circuit. A magnetic recording/reproducing device characterized in that a composite color signal is converted into a composite color signal, converted to a low frequency signal, mixed with a frequency-modulated luminance signal, and recorded. (2) Claim (1) characterized in that the phase-locked loop circuit is provided with a phase adjustment circuit at the front or rear stage thereof, so that the phase of the input or output of the phase-locked loop circuit can be adjusted. The magnetic recording and reproducing device described in 2. (3) The switching timing is the rising edge of the horizontal synchronization signal.
q'l'i+'l The magnetic recording/reproducing apparatus according to claim 1, wherein the period is after the color burst and includes a color burst of the input color signal.