JPH0746875B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing a video signal such as a VTR.

2. Description of the Related Art A conventional magnetic recording / reproducing apparatus is disclosed in, for example, the Journal of Television Society (Vol.36, No.8 1982.8P721).

FIG. 3 is a block diagram of an encoder portion of the conventional magnetic recording / reproducing apparatus, in which 1 is a luminance signal input terminal and 2 and 3 are color signal RY, BY (or I, Q) inputs. Terminals 4, 5 are color signal sub-carrier input terminals for balanced modulation of color signals, 6, 7 are balanced modulators for balanced modulation of color signals, and 8 are balanced modulators 6, 7 An adder for adding the chrominance signals balanced-balanced by, an adder 9 for adding the luminance signal and the chrominance signals balanced-balanced, 10
NTSC (PAL etc.) signal output terminal.

In the conventional magnetic recording / reproducing apparatus configured as described above, the luminance signal Y is input to the luminance signal input terminal 1 and the color signals RY and BY (or I, Q) are input to the color signal input terminal 2. 3 and the color signal subcarrier is input to the color signal subcarrier input terminals 4 and 5. The color signals input to the input terminals 2 and 3 are balanced-modulated by the balanced modulators 6 and 7, respectively, and then added by the adder 8 to form one decoding signal. Adder 8
The combined color signal and the luminance signal input from the input terminal 1 are added by the adder 9 to form an NTSC (PAL, etc.) signal, which is output from the signal output terminal 10.

Problems to be Solved by the Invention However, in the above configuration, when the pedestal potential of the input color signals 2 and 3 changes due to temperature characteristics of the clamp potential, signal deterioration, and the like, there is a problem that carrier leakage increases. Had.

In view of this point, the present invention has an object to provide a magnetic recording / reproducing apparatus in which carrier leakage does not occur even if the pedestal potential changes.

Means for Solving the Problems According to the present invention, a color signal reproduced through a switch is input only for a certain period of a horizontal blanking period, and the input color signal is integrated to obtain an average value to obtain a pedestal potential. An subtractor for subtracting the pedestal potential detected by the integrator from the color signal to obtain a difference signal, and a balance modulator for modulating the difference signal obtained by the subtractor. The present invention provides a magnetic recording / reproducing apparatus characterized in that the color signal which is absolute value data is converted into the difference signal which is relative data, and digital signal processing is performed so that the pedestal potential is always 0.

Effect The present invention has the above-described configuration, which does not cause carrier leakage even when the pedestal potential of the color signal changes due to temperature characteristics or signal deterioration, and is a high-performance NTSC (PAL) without adjustment.
Signal) can be output.

Embodiment 1 FIG. 1 is a block diagram of an encoder portion of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 11 is a luminance signal Y input terminal, 12 and 15 are color signal RY and BY (or I, Q) input terminals, 13 and 16 are control terminals, and 14 and 17 are color signal subcarriers. Input terminal, 18/19 ON / OFF switch, 20/21 integrator, 22/23 subtractor, 24/25 balanced modulator, 26/27 adder, 28 NTSC (PAL etc.) signal output It is a terminal.

The operation of the magnetic recording / reproducing apparatus of the present embodiment configured as described above will be described below. However, the signal shall be digitally processed.

To the color signal input terminals 12 and 15, color signals RY, BY, (or
I, Q) is input. Also, by the control from the control terminals 13 and 16, the on / off switches 18 and 19 are turned on only for a certain period in the H blanking period. The integrators 20 and 21 integrate the input signal for a certain period, obtain an average value, and detect the result as a pedestal potential. Next, the subtracters 22 and 23 find the difference between the input color signals RY and BY and the pedestal potentials obtained from the integrators 20 and 21, respectively. If these input color signals are represented as absolute value data (values digitized by the A / D converter), integrators 20, 2
The output of 1 is the integrated and averaged absolute data. When the absolute data are subtracted by the subtracters 22 and 23, the output from them becomes relative data (that is, data having positive and negative signs). That is, due to such signal processing, the pedestal potential of the color signal is always represented as zero.

Next, the outputs from the subtracters 22 and 23 are balanced-modulated by the balance modulators 24 and 25, respectively. Next, the respective outputs are added by the adder 26 to form one balanced-modulated chrominance signal, which is added by the adder 27 and the brightness signal input from the brightness signal Y input terminal. ) Signal and is output from the signal output terminal 28.

As described above, according to this embodiment, the pedestal potential of the input color signal is detected, and the color signal is converted from the absolute data to the relative data by the potential, so that the pedestal potential is always 0, and the carrier leak does not occur. .

FIG. 2 is a block diagram of an encoder section of a magnetic recording / reproducing apparatus showing a second embodiment of the present invention. In the figure, 29
Is a control terminal, 30 is a subcarrier input terminal, 31 is a luminance signal Y input terminal, 32 and 33 are color signal RY, BY (or I, Q) input terminals, 34 is a control terminal, and 35 is input switching. A switch, 36 is an on / off switch, 37 is an integrator, 38 is a subtractor, 39 is a balanced modulator, 40 is an adder, and 41 is an NTSC (PAL etc.) signal output terminal.

The operation of the magnetic recording / reproducing apparatus of the second embodiment configured as described above will be described below.

However, the signal processing is digital processing. The data of the input signal is absolute data.

RY, BY (or I, input to the color signal input terminal)
Q) is an input selector switch 35 depending on the signal from the control terminal 29.
Are changed to one dot-sequential color signal.

Next, the control signal from the control terminal 34 causes the on / off switch 36 to conduct for a certain period of time during the H blanking period, and after being integrated by the integrator 37, averaged to output the pedestal potential. . The subtracter 38 obtains the difference between the output from the switch 35 and the pedestal potential output from the integrator 37. As a result, the output from the subtractor 38 is converted from absolute data to relative data, and the pedestal potential is always 0.
Next, the output of the subtracter 38 is balanced-modulated by the subcarrier 30 by the balanced modulator 39, and then added by the adder 40 with the brightness signal Y input from the brightness signal Y input terminal 31 to become an NTSC signal. It is output from the signal output terminal 41 (PAL, etc.).

As described above, according to the present embodiment, the pedestal potential is detected, and the absolute data is converted into the relative data by the pedestal potential, so that the pedestal potential can be always 0, and the carrier leak does not occur. Further, as compared with the first embodiment, by providing the signal changeover switch, the number of integrators and balanced modulators can be reduced to half.

In the second embodiment, the integrator is a changeover switch.
It is placed at 3 after 35, but it may be placed before the changeover switch.
When the pedestals of the two color signals are different, each pedestal must have a different integrator and switch the pedestal potential according to the signal.

EFFECTS OF THE INVENTION As described above, according to the present invention, even if the pedestal level of the color signal changes, carrier leakage does not occur and its practical effect is large.

[Brief description of drawings]

FIG. 1 is a block diagram of an encoder section of a magnetic recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of an encoder section of a magnetic recording / reproducing apparatus according to another embodiment of the present invention, and FIG. 3 is a block diagram of an encoder section of the magnetic recording / reproducing apparatus of FIG. 18,19,36 …… ON / OFF switch, 20,21,37 …… Integrator, 2
2,23,38 …… Subtractor, 35 …… Signal selector switch.

Claims (1)

[Claims] 1. An integrator for inputting a color signal reproduced through a switch only during a certain period of a horizontal blanking period, integrating the input color signal to obtain an average value, and detecting the average value as a pedestal potential. The absolute value data is provided with a subtraction unit that subtracts the pedestal potential detected by the integrator from the color signal to obtain a difference signal, and a balance modulation unit that modulates the difference signal obtained by the subtraction unit. A magnetic recording / reproducing apparatus, wherein a certain color signal is converted into the difference signal which becomes relative data, and digital signal processing is performed so that the pedestal potential is always zero.