JPS6351781A - Video tape recorder - Google Patents

Abstract

PURPOSE:To eliminate a fault such as deviation of hue by changing the oscilla tion frequency of an oscillator continuously timewise in response to the speed of variable speed reproduction and converting a reproducing video signal so that the horizontal synchronizing interval of the signals at input/output of a delay element is made constant. CONSTITUTION:Two systems each comprising an oscillator 1, a delay element 2, a frequency divider 3 and an oscillation frequency change means 4 are operat ed, before one delay element is faulty or the rate of change of a frequency is changed largely, the frequency conversion output by other delay element is utilized by a switch 47 and the oscillation frequency for the one delay element is restored to the operationable frequency during that time to apply continuous frequency conversion. The video signal delay element 2 is used in such a way, the clock is changed continuously timewise in response to the speed of variable speed reproduction to apply conversion so that the variable speed reproduction video signal inputted to the delay element 2 is made constant. Thus, the fre quency of the reproduced video signal is brought into a desired value even at the variable speed reproduction and a fault such as asynchronization of the horizontal signal for a monitor television or no coloring is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video cheap recorder, and more particularly to one that makes the synchronization frequency constant during variable speed playback such as high speed search and still playback.

[Conventional technology]

In conventional video cheap recording, when performing variable speed playback such as high speed search or still playback, the trajectory of the head no longer matches the recorded track, so the horizontal synchronization frequency changes in the playback signal.

For example, in the VH8 NTSC system, when performing n-times speed playback, the horizontal synchronization frequency is C(1,5/(525/2)
)X(n-1)XIQ□)% decrease. Also, in still playback, n = O in this equation, and the horizontal synchronization frequency is C(1,5/(525/2))X100:)%
That is, the increase is 0.57%.

[Problem that the invention seeks to solve]

As mentioned above, when variable speed playback is performed in conventional video cheap recording, the synchronization frequency changes, so if the playback speed is increased to 5 times or more, the horizontal synchronization of the monitor TV may be lost or colors may not appear. There was a drawback that there was. Further, even in still images (n=0), there were problems such as hue shift.

This invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a video cheap recorder that makes the synchronization signal interval of the reproduced video signal constant when the reproduction speed is changed. .

[Means for solving problems]

A video tape recorder according to the present invention includes a video signal delay element that transfers charge for a reproduced video signal km using the output of an oscillator as a clock, and an oscillation device that continuously changes the oscillation frequency of the oscillator over time in accordance with the speed of variable speed reproduction. It is equipped with a frequency changing means.

[For production]

In this invention, the frequency of the oscillator is F=FO(1
-kt ), the number of stages of the delay element becomes N
Then, the ratio of the clock (oscillation frequency) at the time of input to the delay element and the clock at the time of output of the variable speed playback video No. 6, that is, the ratio of the input and output frequencies of the delay element is ekN/'FO, and the variable speed playback video No. 6 Frequency conversion of the signal is performed at the above ratio, and the synchronous frequency change during the variable speed reproduction is corrected.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a configuration diagram of a video tape recorder according to an embodiment of the present invention. In the figure, 1 is an oscillator, 2 is a delay element that repeats charge transfer using the output of the oscillator 1 as a clock, and 3 is a VTR.
The playback speed signal 4 of the main body 1o is the oscillation frequency F based on the playback speed signal 3, F = Fo/(1-kt) (x)
This is an oscillation frequency changing means for changing the oscillation frequency. Here again,
F is the reference frequency, k is the frequency change rate, and t is the time. 10 is a VTR body corresponding to a conventional VTR, 11 is a VTR
Variable speed playback video signal from the TR main body 1o, 12 is the oscillator 1
A clock output of 5° indicates a VTR (video tape recorder) according to this embodiment.

The video tape recorder configured in this way has a time T
Assuming that the nth clock pulse is generated at n, n is obtained by integrating equation (1) and becomes the following equation.

According to O n= −−tn(1−kTn) +21, the time Tn at the nth time is Tn = −(1−e−”//co) (3
1, and the nth clock frequency Fn is calculated using formula (3)%
The formula %(4) is obtained. Therefore, the ratio of the input clock frequency to the output clock frequency to the delay element 2 is ekN/'Fo (s), where the number of stages of the delay element is N, and the ratio of the input and output frequencies of the delay element 2 is Also becomes equation (5). Therefore, the frequency conversion of the variable speed reproduction video signal is performed at the ratio of equation (5), and the synchronous frequency change during the variable speed reproduction is corrected.

Note that, in practice, there may be cases where equation (1) cannot be completely satisfied, but if kt (1, then F = Fo/
(1-kt)2F, (1+kt) (6) holds, and the frequency conversion of the present invention can be performed within this range.

FIG. 2 shows a specific configuration of the oscillator 1 and the oscillation frequency changing means 4 in FIG. 1, and will be explained using a still example as variable speed reproduction. Reference numeral 1 is a well-known Astaze multi-vibrator which oscillates at a frequency (Reference: Nobutoshi Kihara, Video Recording Technology, p. 110, Sanpo Publishing).

Here, Rh is a base bias resistance value, C is a feedback capacitor value, Ee is a power supply voltage value, and Eb is a pace bias voltage value. In addition, 13.14 is an oscillation transistor, and 15.16 is an oscillation transistor 13, 14, respectively.
is the collector load resistance of .

The oscillation frequency when Eb = Ee is the reference oscillation frequency f0
Then, F also decreases in proportion to the slight decrease in Eb. Further, from the viewpoint of the operation of the delay element 2, the reference oscillation frequency is, for example, four times the color signal subcarrier frequency, that is, 14.3
MHz is selected, and N is selected to be 910 stages.

3 is a playback speed signal which is at a high level during normal playback and at a low level during still playback, and the resistor 41 and transistor 42 perform an operation of shorting the resistor 43 during normal playback and opening it during still playback. At this time, the resistors 41 and 43 are made so small that they can be ignored compared to Rb, so that they serve as a bias power source for the pace bias Eb. In this state, when switching from normal playback to still mode, Eb is connected to capacitor 44 and resistor 41.
．． It decreases linearly with a time constant determined by 43. Therefore, the oscillation frequency of the oscillator 1, that is, the clock frequency, decreases linearly. Here, in order to obtain a frequency change rate of 0.9943, k may be set to -8967, and if the specifications are selected so that the oscillator 1 and the oscillation frequency changing means 4 jointly titrate equation (6), the desired frequency can be obtained. A conversion is made.

As described above, the same horizontal synchronization frequency as in normal playback can be obtained even in stills, and it is possible to eliminate disturbing noises such as shifts in two hues that are not colored on a monitor television. Furthermore, if kt is selected at speeds other than still speeds, appropriate frequency conversion can be performed.

In addition, in the above example, i! 1. The condition of kt < 1 is required, and if the frequency conversion is continued for more than 2 milliseconds, the frequency conversion rate will change sharply.

Further, the delay element 2 has a limit on the frequency of the oscillator 1, and the highest frequency is usually about 03 times the lowest frequency. Therefore, even if the oscillation frequency decreases, the delay element becomes inoperable, and the frequency conversion shown in FIG. 1 can only be continued for a certain period of time. In the case of continuous frequency conversion, as shown in FIG. 3, the oscillator 1 of FIG. Delay element 2° frequency divider 3. And the oscillation frequency changing means 4 are operated in two systems, and before one delay element becomes inoperable or before the frequency change rate changes significantly, the frequency conversion output from the other delay element is used by the switch 47, and during that time, the frequency conversion output from the other delay element is used. If the oscillation frequency for one delay element is then pulled back to the operable frequency, continuous frequency conversion becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, a video signal delay element is used, and the frequency of the variable speed reproduction video signal input to the delay element is changed by continuously changing the clock in time in accordance with the speed of variable speed reproduction. Since the conversion is made to be constant, the synchronization frequency of the reproduced video signal can be set to the desired value even during variable-speed playback, and this prevents problems such as horizontal synchronization of the monitor TV and lack of color. It has the effect of eliminating

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a video cheap recorder according to an embodiment of the present invention, FIG. 2 is a diagram showing a specific example of the configuration of its oscillator and oscillation frequency changing means, and FIG. 3 is another embodiment of the present invention. It is a figure which shows an example. DESCRIPTION OF SYMBOLS 1... Oscillator, 2... Delay element, 4... Oscillation frequency changing means, 11... Variable speed reproduction|regeneration video signal. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A delay element which receives a variable speed playback video signal and transfers charges using the output of an oscillator as a clock; A video tape recorder comprising: oscillation frequency changing means for continuously changing the oscillation frequency, and converting the horizontal synchronization interval of the reproduced video signal at the input and output of the delay element to be constant.