JPH0767179B2 - Magnetic recording / reproducing device - Google Patents

Description

The present invention relates to the amplitude and clamp potential of a luminance signal and a color difference signal in a VTR for converting a luminance signal and two color difference signals into a time division multiplexed signal and recording the same. The present invention relates to a magnetic recording / reproducing apparatus capable of easily and properly adjusting the above.

[Conventional technology]

FIG. 6 is a diagram showing the structure of a VTR which converts three video signals consisting of a luminance signal and two color difference signals into a time division multiplexed signal (hereinafter referred to as a TTM signal) and records it. In the figure,
1 is a matrix circuit for converting input signals (R, G, B signals) into Y, P _R , P _B signals, 2 is an amplifier for amplifying Y, P _R , P _B signals, 3
Is a clamp circuit for fixing the Y, P _R , P _B signals to a predetermined DC level, 4 is an A / D converter for A / D converting the Y, P _R , P _B signals, and 5 is P _R ,
The P _B signal is thinned out for each line and converted into one C signal, and then the time axis of the Y and C signals is converted to a TTM signal, which is a color difference line sequential time division multiplexing circuit. A D / A converter for A conversion, and 7 is an adjustment terminal for outputting Y, P _R and P _B signals at the time of adjustment.

In the VTR having the configuration shown in FIG. 6, the input signals (R, G, B signals) are converted into Y, P _R , P _B signals in the matrix circuit 1 (see FIG. 7A), Y, P _R , P _B signals. The P _R and P _B signals are adjusted in amplitude and DC level by amplifier 2 and clamp circuit 3,
It is converted into digital data by the A / D converter 4. The color-difference line-sequential time-division multiplexing circuit 5 alternately outputs the two color-difference signals P _R and P _B for each horizontal scanning period and does not serve as the C signal (see FIG. 7B), and the Y signal and the C signal. Are time-compressed respectively, and the Y and C signals are time-divided in one horizontal scanning line period to obtain TTM.
Signal (see FIG. 7 (c)). The TTM signal is D / A converted by the D / A converter 6, FM-modulated and recorded on the magnetic tape. In the VTR configured as described above, it is necessary to adjust the gain of the amplifier 2 in order to set the amplitude of the recorded video signal to a specified value and the clamp potential in order to match the DC level of the recorded video signal. In the conventional adjustment method, the Y, P _R , and P _B signals obtained from the adjustment terminal 7 are input to an oscilloscope or the like. While observing the signal waveform on the oscilloscope, the adjuster changes the gain of the amplifier so that the value of the signal waveform becomes the specified value so that it has the specified amplitude, and the pedestal level of the recorded video signal becomes the specified DC level. Adjust the clamp potential.

[Problems to be Solved by the Invention]

The conventional method of adjusting the amplitude and the clamp potential of the recorded video signal of the magnetic recording / reproducing apparatus is as described above. Therefore, the clamp potential or the black level or the black level in the state where the signal is converted into the digital signal by the A / D converter 4 is used. There is no guarantee that the white level will be the specified value. In fact, since the characteristics of the A / D converter deviate from the ideal characteristics, it can be said that it is almost impossible to obtain a desired digital signal even if the amplitude of the input signal or the clamp potential is adjusted in the analog signal state. If the conventional adjustment method is applied to the A / D converter with the large deviation described above, V
There is a problem in that the reproduced image quality is deteriorated due to an error in the amplitude and signal level of the video signal in the TR output.

The present invention has been made to solve the above problems, and an object thereof is to obtain a magnetic recording / reproducing apparatus in which the amplitude of an input video signal and the clamp potential can be adjusted easily and accurately.

[Means for Solving the Problems]

A magnetic recording / reproducing apparatus according to the present invention includes a clamp means for clamping a video signal composed of a luminance signal and two color difference signals, and a video signal clamped by the clamp means for time division multiplexing to a magnetic recording medium. Time division multiplexing means for converting into a recorded video signal to be recorded, reference signal generating means for generating a reference signal having at least signal levels corresponding to black, white and gray levels of the recorded video signal for a predetermined period respectively, Reference signal inserting means for inserting the reference signal created by the reference signal creating means into at least a part of the vertical blanking period of the recording video signal;
An adjusting terminal for outputting the recording video signal in which the reference signal is inserted by the reference signal inserting means is provided.

[Action]

Since the magnetic recording / reproducing apparatus in the present invention is configured as described above, the video signal on which the conversion error of the A / D converter is superimposed and the reference signal can be obtained at the adjustment terminal. The output signal from the terminal is input to the oscilloscope and the amplitude and amplitude are adjusted so that each level of the recorded video signal is adjusted to the reference signal indicating the black level, gray level, white level and pedestal level inserted in the vertical blanking period of the recorded video signal. By adjusting the clamp potential, the amplitude of the input video signal and the clamp potential can be adjusted in consideration of the conversion error of the A / D converter.

〔Example〕

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

FIG. 1 shows a magnetic recording / reproducing apparatus according to an embodiment of the present invention. In the figure, 1 to 7 are the same as those in the conventional example. Reference numeral 8 is a gate signal generating means for separating a horizontal and vertical synchronizing signal from a recorded video signal to generate a gate pulse, and 9 is a black level, a white level and a gray level (a pedestal level is a pedestal level) of the recorded video signal based on the gate pulse. Reference signal creating means for creating a reference signal having a level corresponding to the black level), and 10 is a reference signal inserting means for inserting the reference signal in the vertical blanking period of the recording video signal.

Next, the operation will be described.

The gate signal generating means 8 separates the vertical and horizontal synchronizing signals from the TTM signal which has been subjected to the color difference line sequential time division multiplexing processing as shown in the conventional example, and creates a gate pulse signal which becomes high in the vertical blanking period. (See Figure 2). The reference signal creating means 9 creates a reference signal for one horizontal scanning line period in which the levels of the respective video signals corresponding to the black level, gray level and white level of the recorded video signal have a certain length, respectively (third). See figure). The reference signal is created by reading the ROM having the data of the reference signal for one horizontal scanning line period. The reference signal creating means 9 creates a reference signal while the gate pulse is high and sends it to the reference signal inserting means 10. The reference signal inserting means 10 inserts the reference signal into the vertical blanking period of the TTM signal.

The TTM signal with the reference signal inserted is shown in FIG. Hereinafter, the TTM signal is D / A converted and recorded. A method of adjusting the amplitude of the video signal and the clamp voltage in the VTR in which the reference signal is inserted and recorded in the vertical blanking period of the recording video signal as described above will be described below. The video signal from the adjustment terminal 7 is input to the oscilloscope, and the oscilloscope is adjusted so that the two signals, the video signal and the reference signal, can be seen overlapping the screen of the oscilloscope. Fig. 5 shows the screen of the oscilloscope at that time. Hereinafter, the gain of the amplifier 2 is changed to adjust the amplitude so that each level of the video signal matches each level (black, gray, and white level in this case) indicated by the reference signal, and the clamp circuit 3 clamps. Change the potential and match each level.

Although the above embodiment has shown the example in which the signal as shown in FIG. 4 is inserted in the vertical blanking period, the form of the reference signal is that there are constant levels corresponding to the black, gray and white levels of the recorded video signal. If it has a period, the same effect is obtained. Further, each level of the recorded video indicated by the reference signal may be a level referred to at the time of adjustment. Further, the reference signal may be inserted in a part of the vertical blanking period. Further, the reference signal may not be inserted after the adjustment is completed.

〔The invention's effect〕

As described above, according to the magnetic recording / reproducing apparatus of the present invention, the clamp means for clamping the video signal composed of the luminance signal and the two color difference signals, and the video signal clamped by the clamp means are time-divided. Time division multiplexing means for multiplexing and converting into a recording video signal to be recorded on a magnetic recording medium, and a reference signal having at least signal levels corresponding to black, white and gray levels of the recording video signal for a predetermined period are created. Reference signal creating means, reference signal inserting means for inserting the reference signal created by the reference signal creating means into at least a part of a vertical blanking period of the recorded video signal, and the reference signal inserting means by the reference signal inserting means. Since it is equipped with an adjustment terminal that outputs the recorded video signal in which the is inserted, the reference signal and the video signal are By displaying superimposed on the screen of the-loop, considering conversion error of the A / D converter, there is an effect that easy adjustment of the amplitude and the clamp potential, and can be accurate.

[Brief description of drawings]

FIG. 1 is a block diagram showing a magnetic recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram for explaining generation of a gate pulse, FIG. 3 is a diagram showing a reference signal, and FIG. 4 is an output. FIG. 5 is a diagram showing a waveform, FIG. 5 is a diagram showing a screen of an oscilloscope at the time of adjustment, FIG. 6 is a configuration diagram showing a conventional magnetic recording / reproducing apparatus,
FIG. 7 is a diagram showing signal waveforms of respective parts of the conventional magnetic recording / reproducing apparatus. In the figure, 7 is an adjustment terminal, 9 is a reference signal generating means,
Reference numeral 10 is a reference signal inserting means. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A clamp means for clamping a video signal composed of a luminance signal and two color difference signals, and a recorded video to be time-division multiplexed with the video signal clamped by the clamp means and recorded on a magnetic recording medium. Time-division multiplexing means for converting into a signal, reference signal generating means for generating a reference signal having a signal level corresponding to at least the black, white, and gray levels of the recorded video signal for a predetermined period respectively, and the reference signal generating means. Reference signal inserting means for inserting the created reference signal into at least a part of the vertical blanking period of the recording video signal, and for adjusting the recording video signal into which the reference signal is inserted by the reference signal inserting means. A magnetic recording / reproducing apparatus having a terminal.