JPS6128273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording/playback device for color video signals, and in particular to a plurality of fixed channels that convert signals of multiple channels subjected to band limitation obtained by Hadamard transform or time division of NTSC color video signals. The present invention relates to a recording and reproducing device that records and reproduces information using a magnetic head.

In this type of recording and reproducing apparatus using a fixed multi-head, it is difficult to directly record the color signal contained in the video signal due to band limitations in the electromagnetic converter.

Therefore, in the past, only the luminance signal component of the video signal (hereinafter referred to as the Y signal) was subjected to Hadamard transform or time division, and this was recorded and reproduced as a converted signal of multiple channels subject to band limitation, and the color signal was reduced. Common methods include performing range conversion or recording and reproducing low-band color difference signals (RY, BY signals). In this case, the device that records and reproduces the color difference signal records and reproduces an FM carrier wave that is frequency-modulated by both color difference signals, the RY signal and the BY signal, in order to record and reproduce the DC component included in the color signal.

By the way, in such a recording/playback device, the playback signal may be missing due to, for example, scratches on the magnetic surface of the magnetic tape or poor contact between the magnetic head and the magnetic tape, and due to this, the playback color difference signal may not be obtained. There is.

However, since the R-Y signal and the B-Y signal have a quadrature phase relationship and the color signal (hereinafter referred to as chroma signal) is reproduced by taking the vector sum of both signals, one of the color difference signals is missing. Even with dropout, level fluctuations, color phase changes, etc. occur in the finally obtained color signal, and these can have a significant adverse effect on reproduced images as color modulation noise.

The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a recording and reproducing device that can eliminate the influence of color modulation noise caused by dropout of color difference signals and that can obtain high-quality reproduced images. .

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

In the figure, reference numeral 1 denotes an NTSC color camera, and the Y signal of this camera 1 is supplied to a converter such as a Hadamard converter 2. This converter 2
is composed of a resistor matrix, etc., and generates multi-channel Hadamard transform signals. In this case, in the illustrated example, only one channel is shown for simplicity, and only the processing of this one channel's worth of Hadamard transform signals will be described below.

That is, a modulator 3 is connected to the output end of the converter 2, and the Hadamard transform signal is FM modulated to generate an FM carrier wave output. Then, the recording side contact R-S of the changeover switch 4 is connected to the output end of this modulator 3.
A recording/reproducing magnetic head 5 is connected via the recording/reproducing magnetic head 5.

In addition, the magnetic head 5 is connected to the changeover switch 4.
Connect the demodulator 6 through the reproduction side contact P-S of
An inverse transformer, for example a Hadamard inverse transformer 7, is connected to the output end of the demodulator 6. This inverse converter 7 is also composed of a resistor matrix, etc., and the demodulator 6
The original Y signal is restored using the output of the Y signal, and this is applied to the mixer 8.

On the other hand, the color difference signals of the NTSC color camera 1, that is, the RY signal and the BY signal are applied to modulators 9 and 10, respectively. These modulators 9,
10 performs FM modulation on the R-Y signal B-Y signal, respectively;
It is designed to generate FM carrier wave output. Furthermore, magnetic heads 13 and 14 for recording and reproduction are connected to the output ends of these modulators 9 and 10 via recording side contacts R-S of changeover switches 11 and 12, respectively.

Demodulators 15 and 16 are connected to these magnetic heads 13 and 14 via reproduction side contacts P-S of the changeover switches 11 and 12, and a color decoder 17 is connected to the output ends of these demodulators 15 and 16. This decoder 17 receives the R-Y signal and B-Y signal demodulated by the demodulators 15 and 16, and generates a chroma signal consisting of the vector sum of both signals.

The chroma signal from the decoder 17 is then applied to the mixer 8 via the analog gate 18. Here, the mixer 8 mixes the chroma signal of the decoder 17 with the Y signal of the inverse converter 7, and reproduces the signal.
An NTSC color video signal is output to an output line 19.

Furthermore, level sensors 20 and 21 are connected to the magnetic heads 13 and 14 via playback side contacts P-S of the changeover switches 11 and 12. These sensors 20 and 21 detect the level of the reproduction signal from the magnetic heads 13 and 14, and the reproduction is performed until this level falls below a predetermined level, for example, to the point where the demodulators 15 and 16 cannot perform demodulation operation under normal conditions. The output is generated when the signal level drops.

The output ends of these sensors 20 and 21 are connected to the analog gate 18 via an OR circuit 22. Here, the analog gate 18 is always in an on state and supplies the chroma signal of the color decoder 17 to the mixer 8, and when an OR output is generated from the OR circuit 22, that is, when either the R-Y signal or the B-Y signal is When a dropout occurs, the output of the OR circuit 22 turns off and prevents the color decoder 17 from generating a chroma signal.

Next, the operation of the invention constructed as above will be explained.

It is now assumed that the recording side contacts R-S of the changeover switches 4, 11, and 12 are closed and in the recording state.
In this state, when a Y signal is generated from the color camera 1, this Y signal is converted into a multi-channel Hadamard conversion signal by the Hadamard converter 2, FM modulated by the demodulator 6, and then the recording side contact R- The signal is applied to the magnetic head 5 via S and recorded on a magnetic tape (not shown) or the like. In this case, although only one channel is shown in the illustrated example, the same applies to the other channels as described above.

On the other hand, the R-Y signal and B-Y signal of the color camera 1 are also FM-modulated by modulators 9 and 10, respectively, and then applied to the magnetic heads 13 and 14 via the recording side contacts R-S of the changeover switches 11 and 12. and recorded on the above-mentioned magnetic tape.

Thereafter, the regeneration side contacts P-S of the changeover switches 4, 11, and 12 are closed to set the regeneration state. Then, the reproduced signal from the magnetic head 4 is given to the demodulator 6, where it is demodulated and then sent to the Hadamard inverse transformer 7.
and is restored to the original Y signal. Of course, in this case, the same applies to other channels as described above.

Furthermore, reproduced signals from the magnetic heads 11 and 12 are also applied to demodulators 15 and 16, respectively, where they are demodulated and then applied to a color decoder 17, where they are generated as chroma signals.

As a result, the Y signal and the chroma signal are mixed in the mixer 8 and sent to the output line 19 as a reproduced NTSC color video signal.

In this state, if the playback signal from the magnetic head 13, that is, the playback R-Y signal, drops out due to poor contact between the magnetic head 13 and the magnetic tape (not shown), the level of the playback signal will drop at this time. An output is generated from the level sensor 20 and is applied to the analog gate 23 via the OR circuit 22. Then, analog gate 23
is turned off, and generation of a chroma signal from the color decoder 17 is prevented. As a result, the reproduction R-
During dropout of Y signal, mixer 8 outputs Y signal.
Only the signal will be sent to output line 19.

Although the dropout of the reproduced signal from the magnetic head 13 has been described here, the dropout of the reproduced signal from the magnetic head 14 or the dropout of the reproduced signal from the magnetic head 1
The same applies to the case where dropout occurs in the reproduction signals No. 3 and No. 14 at the same time.

Therefore, with such a configuration, if dropout occurs in either of the reproduced color difference signals,
Generation of the chroma signal is prevented and only the Y signal is output. As a result, in the area where this dropout occurs, only the Y signal becomes available, and the color component due to the chroma signal component on the screen disappears, making it possible to eliminate the influence of color modulation noise caused by the dropout of the color difference signal, thereby achieving high quality playback. An image will be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications within the scope without changing the gist.
For example, although the above description uses the Hadamard transform method, it can also be applied to a method using time division.

As described above, according to the present invention, it is possible to provide a recording and reproducing apparatus which can eliminate the influence of color modulation noise caused by dropout of color difference signals and can obtain high quality reproduced images.

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. 1... NTSC color camera, 2... Hadamard converter, 3, 9, 10... modulator, 4, 11, 1
2... Selector switch, 5, 13, 14... Magnetic head, 6, 15, 16... Demodulator, 7... Hadamard inverse converter, 8... Mixer, 17... Color decoder, 18... Analog Gate, 19... Output line, 20, 21... Level sensor, 22...
...OR circuit.

Claims (1)

[Claims] 1 means for dividing the luminance signal component (Y signal) of the color video signal into converted signals of a plurality of channels and recording and reproducing the same;
B-Y); means for generating a chroma signal from the reproduced signal of the color difference signal and mixing it with the reproduced luminance signal to generate a reproduced color video signal; 1. A recording and reproducing apparatus comprising: a level sensor which detects each signal and generates an output when the level is below a predetermined level; and means for preventing the generation of the chroma signal based on the output of the level sensor.